Directional Sound Evacuation - Marine

What is Localizer®

technology?

Fire Safety

Fire at Sea

Confusion in smoke

Signs lost in smoke

In the context of Marine safety, Directional Sound Evacuation (DSE) has the 

following advantages:

- Language independent - “Audible exit signs”

- up to 75% improvement in exit times - Time saved = Lives saved

- Ideal in poor visibility (dense smoke) - Lower cost – easy retrofit

- Works in open areas, corridors, stairs - ADA & DDA conformance

Localizer® directional sound is a broadband, multi-frequency (“white noise”) sound. 

The sound source is easily and quickly located by our ears, making it ideal for rapid 

ship evacuation. Details of the technology and the wide variety of applications can 

be found on the website www.soundalert.com

Developed at Leeds University, the technology is patented in the UK, USA, Australia 

and Hong Kong, with applications being processed in EU, Canada and Japan. 

Conventional General Alarm sounders and PA systems efficiently warn people in 

the event that evacuation is necessary, but can give no indication of exit routes. 

Illuminated exit signs and low location lighting will help only if visible and not 

obscured by smoke. Localizer-equipped DSE evacuation beacons can identify the 

nearest evacuation routes even in dense smoke. DSE was recently awarded the 

Fire Industry Council’s product innovation award and the RINA~Lloyds Register of 

Shipping Safer Ship award

The Scandinavian Star disaster showed that rapid evacuation of the smoke-filled 

areas would have saved lives. Low-Location Lighting has limitations in smoke filled 

environments where visibility is severely restricted – the recent Nieuw Amsterdam 

incident illustrated this. LLL gives no indication of direction to the nearest exit and is 

ineffective in open spaces. Normal wisdom is that evacuees should crouch and 

follow the evacuation route at floor level. However, whilst hot smoke rises in a stable 

still atmosphere, it quickly fills down to floor level when cooled by water mist 

extinguishing systems or disturbed by ventilation systems and people movement. 

Directional sound technology offers an additional or alternative evacuation method 

giving audible assistance that can considerably improve exit times. Localizer 

evacuation beacons positioned at carefully chosen locations guide people along 

escape routes. In addition to corridors and stairs, Localizer can also guide people 

out of open spaces, which represent as much as 40% of modern passenger ships, 

and today have no evacuation aids effective in smoke. 

The UK Government’s Maritime & Coastguard Agency recently completed an 

extensive series of independent tests with University of Strathclyde in which over 

400 volunteers participated in trials simulating accommodation, corridors, stairs and 

open spaces with and without smoke. In these trials improvements of up to 75% in 

evacuation times were recorded in smoke and 35% in perfect visibility. Following 

these trials, the Governments of UK and Germany are proposing Directional Sound 

Evacuation to the United Nations’ IMO for approval within SOLAS regulations as an 

alternative to Low Location Lighting and mandatory fitment in open spaces.

In May 2002, IMO’s Maritime Safety Committee commented: “directional sound is at 

least as effective as Low Location Lighting and its use is not diminished by smoke”.

Full details on the MCA’s website: www.directionalsoundevacuation.com

Implementation can be proposed using the new SOLAS Chapter II-2 Regulation 17 

“Alternative design & arrangements” for a “case by case” approval. 

Systems can be installed today as an extension to existing PA/GA systems and 

hence require no additional type approval.

* The Localizer is the registered trademark of Sound Alert Technology plc.

Taurus Park, Europa Boulevard, Warrington, WA5 5YT, United Kingdom

Tel: +44 (0)1925 446139 Fax: +44 (0)1925 446139 www.soundalert.com

Fire Industry Council 

Product Innovation 

Award 

Design 

Council

Award
I:\CIRC\MSC\1168.doc 

INTERNATIONAL MARITIME ORGANIZATION

4 ALBERT EMBANKMENT 

LONDON SE1 7SR 

Telephone: 020 7587 3152 

Fax: 020 7587 3210 

IMO 

E

Ref. T4/4.01 MSC/Circ.1168 

1 June 2005 

INTERIM GUIDELINES FOR THE TESTING, APPROVAL AND MAINTENANCE OF 

EVACUATION GUIDANCE SYSTEMS USED AS AN ALTERNATIVE TO 

LOW-LOCATION LIGHTING SYSTEMS 

1 The Maritime Safety Committee, at its seventy-fifth session (15 to 24 May 2002), recognized 

the need for the development of guidelines for the testing, approval and maintenance of evacuation 

guidance systems used as an alternative to low-location lighting systems required by SOLAS 

chapter II-2 and the FSS Code. 

2 The Committee, at its eightieth session (11 to 20 May 2005), having considered a proposal by 

the forty-ninth session of the Sub-Committee on Fire Protection, approved the Interim Guidelines for 

the testing, approval and maintenance of evacuation guidance systems alternative to the low-location 

lighting systems, set out in the annex. 

3 Member Governments are invited to apply the annexed Interim Guidelines and submit to the 

Sub-Committee on Fire Protection information on experience gained in the implementation of the 

Interim Guidelines and on any progress made in the development of the testing, approval and 

maintenance of evacuation guidance systems. 

4 Member Governments are also invited to bring the annexed Interim Guidelines to the 

attention of ship designers, shipowners, ship operators, shipbuilders and other parties involved in the 

design, construction, testing, approval and maintenance of evacuation guidance systems. 

*** 

MSC/Circ.1168 

I:\CIRC\MSC\1168.doc 

ANNEX 

INTERIM GUIDELINES FOR THE TESTING, APPROVAL AND MAINTENANCE OF 

EVACUATION GUIDANCE SYSTEMS USED AS AN ALTERNATIVE TO 

LOW-LOCATION LIGHTING SYSTEMS 

1 Scope 

The purpose of these Guidelines is to provide standards for the testing, approval and maintenance for 

alternative systems to low-location lighting systems required by SOLAS regulation II-2/13.3.2.5.1 

and chapter 11 of the FSS Code. 

2 Testing

2.1 Test for corridors should be performed in reduced visibility using theatrical (white) smoke 

with an Optical Density at least OD 0.5 m-1∗

. Measuring equipment should conform to a standard 

acceptable to the Administration. 

2.2 If the system is to be installed in public spaces, the test should be performed in reduced 

visibility using theatrical (white) smoke with an Optical Density at least OD 0.1 m-1.

2.3 Test for stairway enclosures should be performed in clear (no smoke) conditions. 

2.4 A minimum 80% of the participants should reach the pre-designated exit with a speed of 

movement of at least 0.7 m/s calculated using the distance measurement of the optimum route. 

Participants achieving a speed of movement of less than 0.7 m/s should be deemed to have failed. 

There is no speed of movement criterion applied to stairway enclosure tests. 

2.5 The maximum percentage of participants choosing failed exits should not exceed the value of 

2% for public spaces and 5% for accommodation areas, corridors and stairway enclosures. 

2.6 In the public space configuration when testing with two correct exits, no more than 15% of 

the participants may choose the more distant exit. 

2.7 There should be a minimum of 60 participants for each test - being at least 8 and not more 

than 12 of each age group 16-25, 26-35, 36-45, 46-55, 56-65, 66-75 with an average of 

45-55% male/female of the entire group. 

2.8 A ìcontrolî test should be performed with no guidance system in operation in order to 

demonstrate that there is no significant inherent bias to favour the pre-designated exit. Participants 

of the ìcontrolî test should not participate in any previous or subsequent tests. 

2.9 For the purpose of this section: 

.1 a ìcorrect exitî is an exit to which the evacuation guidance system intentionally 

guides participants; 

 

∗

 Refer to the United Kingdom Governmentís Health and Safety Executive (HSE) 1998 report: OTH 533 Emergency 

Way Guidance Lighting Systems (http://www.hse.gov.uk/research/othpdf/500-599/oth533.pdf). 
MSC/Circ.1168 

ANNEX 

Page 2 

I:\CIRC\MSC\1168.doc 

.2 participants arriving at any of the ìfail exitsî are deemed to have ìfailedî the test and 

should be stopped at that point; 

.3 only one participant should be in the test at a time in order to preclude any crowd 

behavioural influence; 

.4 the test area should be illuminated by the emergency lighting as required by SOLAS; 

and 

.5 during the test signage other than those being part of the test should not be used. 

3 Test facility design 

3.1 Public spaces

3.1.1 If the system is intended to be installed in public spaces, the test facility should be designed 

so that participants are required to navigate to a pre-designated exit across a public space, where the 

shortest distance to that exit is not along a wall. A minimum of two exits should be provided to test 

the ability of participants to identify and proceed to an exit within an open space. An additional fail 

exit should be located 2 to 3 m from each correct exit. 

3.1.2 The test room should be not less than 15 m by 10 m with the start point and pre-designated 

exit being on the long sides, diagonally opposite each other, such that the distance around the walls 

is approximately equal in either direction. The density of the smoke should be great enough to 

prevent a participant from being able to see no more than half to two-thirds of the distance to the 

nearest exit OD 0.1 m-1. Direct distance between start and a correct exit should be not less 

than 12 m. 

3.2 Accommodation areas and corridors

The test layout should be such that participants should be required to navigate correctly their way to 

a pre-designated exit via at least four decision points including at least two cross-junctions and at 

least one T-junction. It should not be possible to navigate the correct route by remaining attached to 

one continuous wall. The correct route should include the placement of a non-exit door within 2 to 

3 m of the correct exit door. A non-exit door is a fail exit. The total distance travelled over the 

correct route should be not less than 25 m, with the distance between decision points being not less 

than 5 m. 

3.3 Stairway enclosures

Participants should be required to use the stairway enclosures to a pre-designated floor. The 

participants should enter the stairway enclosures from a mid-point where each will be instructed by 

the guidance system to proceed either up or down. The option of up or down should be randomly 

chosen. 

4 Participant briefing 

Participants to be briefed on the purpose of the test and the technology to be tested, using the 

proposed briefing technique that would be used in the implementation on board ship, e.g. the briefing 
MSC/Circ.1168 

ANNEX 

Page 3 

I:\CIRC\MSC\1168.doc 

given during lifeboat drill, instructions on backs of cabin doors or via the shipís public address 

system, etc. No briefing should be given on the route, test layout or numbers of exits. 

5 Approval 

All systems should be approved by the Administration for compliance with the Performance 

standards for evacuation guidance systems (MSC/Circ.1167) developed by the Organization and, for 

electrically powered systems, IEC 60092 Electrical Installations in Ships. Installation requirements 

should be included in the approval procedures, and individual onboard arrangements should be 

verified accordingly. 

6 Maintenance 

6.1 All elements of the system should be visually examined and checked at least once per week, 

and a record thereof should be kept. All missing, damaged or inoperable elements should be 

replaced. 

6.2 All systems should have their signal tested at least once every five years. Readings should 

be taken on site. Should any reading be found to be outside manufacturerís tolerances, then that 

element of the system should be replaced. 

__________ 
News Update

American Bureau of Shipping June 2002

Vol.11, No.3

Maritime Safety Committee’s

75th Session

15 to 24 May 2002

Refer also: www.eagle.org / News and Events / Regulatory Information

ABS REGULATORY AFFAIRS: INTERNATIONAL REGULATION NEWS UPDATE, JUNE 2002 (VOL 11, NO.3)

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MSC – 75th Session (15 - 24 May 2002)

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International Regulation News Update June 2002

Refer also: www.eagle.org / News and Events / Regulatory Information

Regulatory Development Ship+ Application

OPENING REMARKS (page 2)

MARITIME SECURITY (pages 2 & 3) All Ships

Ship Security Plans

Security Alarm

Automated Identification Systems (AIS)

IMO Number

Continuous Synopsis Record (CSR)

Container Security

SOLAS AMENDMENTS AND INTERPRETATIONS (pages 3 & 4)

Enhanced Surveys Oil Tankers and Bulkers

IMDG Code All Ships

Ships Under Construction on 1 July 2002 All Ships

PERMANENT ACCESS (pages 4 - 6) Oil Tankers and Bulkers

Draft SOLAS Regulation

Ship Structures Access Manual

Draft Technical Provisions – Bulk Carriers

Draft Technical Provisions – Oil Tankers

BULK CARRIER SAFETY (pages 6 & 7) Bulk Carriers

Water Ingress Monitoring/Alarm

Dewatering Systems

Hatch Cover Design Loads

MISCELLANEOUS (pages 7 - 10)

Safety of Large Passenger Ships Passenger Ships

Passenger Ship Evacuation Analysis Passenger Ships

STCW Transitional Period to End All Ships

Cargo Securing Strength All Ships

Asbestos Monitoring Guidelines All Ships

Testing of Watertight Doors All Ships

Thermal Protection Assessment All Ships

Immersion and Anti-exposure Suits All Ships

ISM Major Non-Conformities All Ships

Emergency Towing Arrangements Existing Oil Tankers

HSC Model Test Guidelines High Speed Craft

FIRE SAFETY(pages 10 & 11) All Ships

FTP Code Type Approval

Smoke Detectors

Smoke Control

 ( + “ships” are all self propelled vessels)
MSC – 75th Session (15 - 24 May 2002)

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OPENING REMARKS

The 75th session of the Maritime Safety

Committee (MSC) met from 15 to 24 May 2002

at IMO Headquarters in London. Secretary

General William A. O’Neil highlighted a number

of ongoing efforts but focused on this session’s

most prominent agenda item -- the progress

made by an intersessional working group,

funded by the United States of America, to

develop regulation aimed at improving maritime

security.

A number of amendments to the SOLAS

Convention were adopted together with MSC

Circulars containing recommended guidelines

supplementing SOLAS regulations.

MARITIME SECURITY

Work continued on the development of a revised

SOLAS Chapter XI to include maritime security

regulations in addition to maritime safety. A

second intersessional working group funded

again by the USA is scheduled for 9-13

September so that a final draft of the revised

Chapter XI and a new Maritime Security Code

can be completed for adoption at the December

2002 Diplomatic Conference.

Draft requirements approved at MSC 75 include

the following provisions, which will be subject to

survey and periodic certification by a special

agency of the Administration or on behalf of the

Administration by a recognized organization with

special security expertise.

Ship Security Plans

Passenger ships, cargo ships >500 gt and

mobile offshore drilling units must be provided

with a ship security plan. The plan should

contain procedures and measures to prevent

introduction of weapons; identify shipboard

restricted areas; provide procedures for

responding to security threats and evacuation;

assign shipboard security duties including

auditing, training and drill procedures.

It is possible that the ship’s Security Plan may

be combined with the ISM Safety Management

System.

New positions ashore and onboard by a

designated ship and Company Security Officer

will be required and responsible for implementing

these plans. Records are to be maintained to

document the plan’s effective implementation.

Security Alarm

Every cargo ship >500 gt, passenger ship and

drilling unit constructed on/after 1 July 2004 will

be required to be fitted with a ship security alarm

which shall automatically alert shore authorities

that the ship’s security is under threat or is

being compromised. The alert shall continue

until it is deactivated by an authorized

personnel. The alert shall not be sent to other

ships and shall not raise an alarm on board.

Existing passenger ships, tankers, bulk carriers

and high speed craft will need to be retrofitted

with such alarms by the first radio installation

survey after 1 July 2004. All other cargo ships

>500 gt and drilling units need to comply by the

first radio installation survey after 1 July 2006.

Automated Identification System (AIS)

Agreement could not be reached on one of the

four proposals tabled on accelerating the

implementation dates for retrofitting AIS to ships

(other than passenger ships and tankers)

between 300 and 50,000 gt. The current range

varies from 2004 to 2007 according to cargo ship

size. The proposals range from 1 July 2004

(USA) to 2006 (Russia) with the European Union

proposing a middle range beginning 1 July 2004

with full implementation by 1 July 2005.

IMO Number

The ship’s assigned IMO Number is to be

marked externally on the ship’s stern, the front

of the superstructure or on both sides of the ship

by the plimsol mark. It is also to be marked

internally on a bulkhead of a machinery space, a

pump room (for tankers), or a ro-ro space (for roro ships) or on a hatchway (for bulk carriers).

This applies to passenger ships >100gt and

cargo ships >300 gt built on/after the expected

entry into force date (1 January 2004) and to

existing ships at the date of the first dry docking

due thereafter.

Continuous Synopsis Record (CSR)

All passenger ships >100gt and cargo ships

>300 gt are to be provided with a CSR which

indicates the ship’s history from the date on

which this regulation is scheduled to enter into

force (1 January 2004). The Administration is to
MSC – 75th Session (15 - 24 May 2002)

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issue the CSR which shall at least contain the

history of the ship’s name, registered bareboat

charterer, Flag, class society, ISM (DOC and

SMC) issuer and registered owner.

Container Security

The shipper shall ensure the security of a loaded

container before it is offered for shipment on

board. Two alternative means to ensure security

are under consideration:

• Electronic Seal – records the seal’s unique

identification number for the container’s

number to which it is affixed and the status

of the seal based on ISO Standard 18185,

“Freight Containers - Radio Frequency

Communication Protocol for Electronic

Seal”; and

• Mechanical Seal – a high security seal that

is uniquely numbered. Reference has been

made to ASTM Standard F832,

“Classification of Security Seals, Level D”.

SOLAS AMENDMENTS AND INTERPRETATIONS

Enhanced Surveys

Resolution A.744(18) on enhanced surveys was

amended to bring it in line with IACS Unified

Requirements that are already implemented by

IACS Member Societies. The amendments are

contained in resolution MSC.125(75) and include

the following provisions which enter into force on

1 January 2004:

Prompt and Thorough Repair on oil tankers and

bulk carriers is to be carried out at the time of

survey, except if adequate repair facilities are

not available. The repair is to be permanent so

as to alleviate the need to record it as a

condition of classification to be followed up at

the next survey.

Thickness Measurements of corrugated

transverse bulkheads between the first two cargo

holds in bulk carriers are contained in a new

Annex. In order to assess their strength to

resist the flooding of the No.1 cargo hold each

vertical corrugation, corrugation flange, web

shedder plate and gusset plate at two transverse

bands is to be measured. This applies to

existing single side skin bulk carriers (of 150 m

length or above, carrying solid bulk cargoes

having a density >1.78 tons/m3, constructed

before 1 July 1999. Additionally, thickness

measurements carried out at any of the required

surveys, if not carried out by the class society

itself, must be witnessed by a surveyor to the

extent necessary to control the measurement

process to assure that the measurements

represent the actual average condition of the

structural member.

Annual Survey Requirements for the foremost

cargo hold of existing bulk carriers described

above which do not have a sufficient number of

cargo holds to meet the damage stability

requirements of SOLAS regulation XII/9.1. For

bulk carriers between 5-15 years of age a

minimum of 25% of the frames are to undergo

close-up survey. This increases to 100% at

ages exceeding 15 years.

Accelerated Implementation of survey

requirements for bulk carriers and tankers more

than 15 years of age require the intermediate

survey to be the same extent as the prior

special survey, except for pressure testing of

cargo holds and tanks unless otherwise

considered necessary by the surveyor.

An overall survey of every ballast tank is to be

carried out for bulk carriers at >10 years of age

and tankers >5 years of age at their intermediate

survey. Further, close-up surveys of ballast and

cargo tanks are to be to the same extent as the

previous periodical survey for tankers >10 years

of age. Previously, these intermediate survey

requirements were not specified for bulk carriers

and were required for tankers more than 10 yrs

of age.

Also, ballast tanks sharing a common plane with

a heated cargo tank must be internally

examined on an annual basis for tankers

exceeding 15 years of age.

IMDG Code

Resolution MSC.123(75) contains amendments

to SOLAS Chapter VII that will, when it enters

into force on 1 January 2004, require packaged

goods and goods carried in bulk to comply with

the International Maritime Dangerous Goods

(IMDG) Code. This applies to all cargo ships

regardless of size and to ships carrying more

than 12 passengers.

However, not all of the provisions of the Code

have been made mandatory and the following

provisions remain voluntary:
MSC – 75th Session (15 - 24 May 2002)

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• Training of officers and ratings responsible

for cargo handling on ships and shore-based

personnel;

• Transport of explosives relative to hazard

division, compatibility and classification;

• The determination of flash point (a measure

of risk of formation of explosive or ignitable

mixtures when the liquid escapes from its

packing);

• Column 15 of the Dangerous Goods List -

the emergency schedule (EmS) number to

identify when the "Emergency Procedures

for Ships Carrying Dangerous Goods" is to

be provided by the shipper;

• Column 17 of the Dangerous Goods List -

properties and observations of goods;

• The transport schedules for class 7

Radioactive Material;

• Multi-modal Dangerous Goods Form

• Special provisions in the event of an incident

and fire precautions.

Ships Under Construction on 1 July 2002

The MSC agreed that the term first survey

includes the initial survey in addition to the

annual and periodical surveys when applying the

retroactive requirements calling for the fitting of

the following equipment at the first survey

on/after 1 July 2002 (or 2003 for AIS):

• Global Positioning System (GPS)

• Automated Identification System (AIS);

• Voyage Data Recorder (VDR) for passenger

ro-ro ships.

Under SOLAS, the Initial Survey includes all the

survey work necessary to issue a certificate

before the ship is put in service. Therefore, a

ship built before 1 July 2002 which is put in

service and issued a valid safety equipment or

passenger safety certificate on/after 1 July 2002

(or 2003 for AIS) needs to comply with the

regulations referenced above when it is put into

service.

Conversely, a ship which is put in service and

issued certificates before 1 July 2002 (or 2003

for AIS) has until the date of the first annual or

the first renewal survey for safety

equipment/passenger safety, whichever occurs

first after 1 July 2002, (or 2003 for regulation

V/19.2.4) to comply.

PERMANENT ACCESS

Draft SOLAS Regulation

A draft SOLAS regulation applicable to oil

tankers > 500 gt and bulk carriers > 20,000 gt,

constructed on or after 1 January 2005 was

presented to the MSC for approval. The MSC

decided to delay final review and adoption until

MSC 76 (December 2002).

The draft regulation calls for each space within

the cargo area to be provided with a permanent

means of access to enable, throughout the life of

a ship, overall and close-up inspections and

thickness measurements of the ship’s

structures to be carried out by the

Administration, the Company, as defined in

regulation IX/1, and the ship’s personnel. The

means of access is to comply with the

requirements of regulation II-1/12-2 and with a

mandatory set of Technical Provisions.

Where a permanent means of access may be

susceptible to damage during normal cargo

loading and unloading operations or where it is

impracticable, the Administration may allow, in

lieu, the provision of portable means of access

such as staging, moveable platforms and

ladders as specified in the Technical Provisions,

provided the means of attaching, rigging,

suspending or supporting the portable means of

access forms a permanent part of the ship’s

structure. All portable equipment shall be

capable of being readily erected or deployed by

ship’s personnel. The means of access shall be

subject to survey prior to, or in conjunction with,

its use in carrying out surveys in accordance

with regulation XI/2.

Safe access to cargo holds, cofferdams, ballast

tanks, cargo tanks and other spaces in the

cargo area shall be direct from the open deck

and such as to ensure their complete

inspection. Access to double bottom spaces

may be from a pump-room, deep cofferdam, pipe

tunnel, cargo hold, double hull space or similar

compartment not intended for the carriage of oil

or hazardous cargoes.

Tanks, and subdivisions of tanks, having a

length of 35 m or more shall be fitted with at

least two access hatchways and ladders, as far

apart as practicable. Tanks less than 35 m in

length shall be served by at least one access

hatchway and ladder. When a tank is

subdivided by one or more swash bulkheads or
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similar obstructions which do not allow ready

means of access to the other parts of the tank,

at least two hatchways and ladders shall be

fitted.

Each cargo hold should be provided with at least

two means of access as far apart as practicable.

In general, these accesses should be arranged

diagonally, e.g. one access near the forward

bulkhead on the port side, the other one near the

aft bulkhead on the starboard side.

Horizontal openings, hatches or manholes shall

be sized to allow a person wearing a selfcontained air-breathing apparatus and protective

equipment to ascend or descend any ladder

without obstruction and also provide a clear

opening to facilitate the hoisting of an injured

person from the bottom of an internal space. The

minimum clear opening shall not be less than

600mm x 600mm. When access to a cargo hold is

arranged through the cargo hatch, the top of the

ladder shall be placed as close as possible to

the hatch coaming. Access hatch coamings

having a height greater than 900mm shall also

have steps on the outside.

Vertical openings, or manholes, in swash

bulkheads, floors, girders and web frames

providing passage through the length and

breadth of the space, shall have a minimum

opening not less than 600mm x 800mm at a height

of not more than 600mm from the bottom shell

plating unless gratings or other foot holds are

provided.

Ship Structure Access Manual

A ship’s means of access to carry out “close-up”

inspections and thickness measurements shall

be described in a Ship Structure Access Manual

approved by the Administration, an updated

copy of which shall be kept on board. The Ship

Structure Access Manual shall include the

following for each space in the cargo area:

• plans showing the means of access within

each space, with appropriate technical

specifications and dimensions, to enable

close-up inspections to be carried out;

• instructions for inspecting and maintaining

the structural strength of all means of

access and means of attachment, taking

into account any corrosive atmosphere that

may be within the space;

• instructions for rigging and use of portable

equipment; and

• an inventory of all portable means of access

with safety instructions for the rigging.

Draft Technical Provisions – Bulk Carriers

Cargo Holds (Vertical Structure) - Permanent

vertical access to allow for inspection of a

minimum of 25% of the total number of hold

frames port and starboard equally distributed

throughout the hold including at each end in way

of transverse bulkheads.

In no case should this arrangement be less than

three permanent means of vertical access.

Means to readily secure safety cages to the

permanent means of access are to be provided.

A means of portable access may be used to

gain access over the sloping plating of lower

hopper ballast tanks to the lower brackets.

Cargo Holds (Overhead Structure) - Three

permanent means of access shall be fitted at

both ends of sides of the cross deck and in the

vicinity of the centerline. Each access is to be

accessible from the cargo hold or directly from

the main deck and is to be installed between

1.8m to 2.5m below the deck. Alternatively, if the

height of the overhead structure of the cross

deck is less than 17m, a movable means of

access (e.g., hydraulic arms with a stable base

or wire lift platforms) may be accepted.

Lower Hopper Tanks – Tanks ≥ 5m in height are

to be provided with one longitudinal, continuous

permanent means of access for the full length of

each tank, adjacent to side shell at 1.8m to 2.5m

below the deck with vertical access ladders to

the main deck access. Access holes are to be

arranged at each transverse ring web within

600mm of the tank base. Where the bottom web

frame rings have a web height greater than 1m,

step rungs/grab rails are to be provided to allow

safe access over each transverse web frame ring

and bottom web frame rings. Portable ladders

may be used for a tank height < 5m.

Top Side Tanks - Tanks ≥ 5m in height are to be

provided with one longitudinal, continuous

permanent means of access is to be provided for

the full length of each tank, adjacent to side

shell at 1.8m to 2.5m below the deck with vertical

access ladders to the main deck access. Three

(3) permanent vertical ladders are to be provided
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from bottom shell to the top of the lower hopper

plating at side shell connection fitted at each

end and mid-span. Access holes are to be

arranged at each transverse ring web within

600mm of the tank base. Where the bottom web

frame rings have a web height greater than 1m,

step rungs/grab rails are to be provided to allow

safe access over each transverse web frame ring

and bottom web frame rings. Portable ladders

may be used for a tank height < 5m.

Draft Technical Provisions – Oil Tankers

Cargo & Inboard Ballast Tanks

Overhead Structure - is to be provided with one

continuous athwartship permanent access

arranged at every deck transverse on the clean

(unobstructed) side of the web plating from 1.8m

to 2.5m below the deck. Lightening holes (300mm

φ) shall be cut in the web plating, (each side of

and adjacent to) each tripping bracket at a

minimum of 3 locations. The athwartship

accesses are to be accessible from a

continuous longitudinal permanent access

provided at the longitudinal bulkhead. Where a

longitudinal bulkhead contains attached framing,

the access shall be provided on that side.

Portable ladders may be used for a tank height

< 5m.

Vertical Structure - is to be provided with

permanent access unless the tank height is less

than 5m in which case portable ladders may be

an acceptable alternative.

Wing Ballast Tanks > 5m width

Overhead Structure - is to be provided with one

continuous longitudinal permanent access

provided for the full length of the tank from 1.8m

to 2.5m below the deck with means to pass

through swash bulkheads. Vertical access

ladders are to be provided at each end of the

tank and at its mid-span. Portable ladders may

be used for a tank height < 5m.

Vertical Structure - is to be provided with

permanent access to each transverse web

between horizontal stringers from the upper

knuckle point of the bilge hopper section to the

main deck. If the distance between these

members < 5m, portable ladders may be used

BULK CARRIER SAFETY

Water Ingress Monitoring/Alarm

IMO’s first action taken relative to the UK’s

second formal inquiry into the loss of Derbyshire

is contained in a set of new requirements for

water ingress alarms.

Single and double side skin bulk carriers >500

gt built on/after 1 July 2004 (when they are put in

service) and existing bulk carriers (by the first

intermediate or renewal survey carried out

thereafter) will need to be provided with water

level alarms giving audible and visual indication

on the navigation bridge when water is detected:

• at 0.5m and 15% cargo hold depth (but not

more than 2m) shall be fitted at the aft end

of each cargo hold. Bulk carriers which do

not meet the damage stability requirements

of SOLAS regulation XII/9.2 need only be

provided with the higher level alarm;

• at a level corresponding to 10% capacity of

any ballast tank forward of the collision

bulkhead; and

• at 0.1m above the deck of any dry or void

space (other than a chain locker) which

extends forward of the foremost cargo hold.

There was some support for the U.K. proposal to

accelerate the implementation schedule for

existing bulk carriers from the first intermediate

or renewal survey carried out after 1 July 2004 to

the first annual survey carried out thereafter.

BIMCO has reported that they may submit a

paper to MSC 76, which is scheduled to adopt

this regulation, arguing against such a proposal

recognizing that the fitting of these alarms,

particularly in cargo holds, will require flame

cutting, welding, staging, cabling, etc., which is

more safely carried out when the ship is in dry

dock as opposed to the use of riding crews

during operation.

IACS has adopted Unified Requirement S24

which contains a different implementation

schedule as well as system requirements. UR

S24 calls for single side skin bulk carriers >500

gt built on/after 1 January 2003 (when they are

put in service) and existing bulk carriers (by the

first intermediate or renewal survey carried out

thereafter if >10 years of age on 1 January 2003

or by 10 years of age if <10 years of age on 1

January 2003) will need to be provided with water

level alarms giving audible and visual indication
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on the navigation bridge when water is detected

at 2m above the cargo hold bottom.

Dewatering Systems

Subject to adoption by MSC 76 in December

2002, bulk carriers >500 gt built on/after 1 July

2004 (when they are put in service) and existing

bulk carriers (by the first intermediate or renewal

survey carried out thereafter) will need to be

fitted with a means of dewatering ballast tanks

and dry spaces, any part of which extends

forward of the collision bulkhead. Means of

operation shall be readily accessible from an

enclosed space that is accessible from the

navigation bridge or propulsion control position

without having to traverse exposed decks.

Hatch Cover Design Loads

Based on the UK’s presentation of results of

model tests carried out in association with the

the MV Derbyshire casualty at Lancaster

University, the MSC tasked the SLF SubCommittee to update the design loads for hatch

covers contained in the 1966 Load Line

Convention taking into account the above model

test results.

These tests were carried out in head, bowquartering and beam seas on one Panamax (83k

displacement) and two Capesize (188k and 204k

displacement) bulk carriers. Vertical, transverse

and horizontal loads on the hatches were

measured on deck from mid-length forward, for

three speeds (0, 13.5 and 15.5 knots). The

tests did not indicate any clear trends as to the

influence of speed on the vertical loads as there

were inconsistent readings across the range of

test conditions.

The Model Test Report places emphasis on the

predicted longitudinal loads as they were well

above the limiting loads of hatch covers to avoid

longitudinal displacement -- reported to be

45kPa by industry sources.

In light of this, the UK expressed concern that

IACS Unified Requirement S21, which provides

for a more robust hatch cover than the 1966

Load Line Convention, may also need to be

revised. IACS UR S21 requires net thickness

(after a corrosion margin is deducted) to be used

and takes into account design speed, coaming

height above water, hull form and the hatch

cover’s longitudinal location. Preliminary results

of IACS current assessment of UR S21 that

become available will be presented to the SLF

Sub-Committee during its upcoming 45th

Session (22-26 July 2002).

IMO discussions are currently focused on new

bulk carriers, although IMO noted IACS’

announcement to implement an equivalent

requirement to existing bulk carriers and plans

to wait for this outcome.

FSA Studies

The MSC considered progress reports from

studies not yet completed (UK/International FSA

Collaboration) and final reports from completed

studies (by Norway/ICFTU, Japan and IACS) in

developing a list of preliminary risk control

options (RCO’s).

The MSC was conscious of the fact that the list

is tentative pending receipt of final FSA study

reports, that some of the RCO’s take into

account the enhanced survey amendments to

A.744(18) presented above, and that further

study is needed to evaluate applying an RCO in

conjunction with others or individually.

The approved list of tentative RCO’s address:

• Improved structural robustness, reserve

buoyancy (focsle/bulwark), and corrosion

control & protection of the hull envelope;

• Improved robustness of hatch covers, deck

fittings and their closing mechanisms;

• Enhanced evacuation warnings and

abandonment provisions;

• Operational enhancements including

increased control of loading capabilities and

weather routing; and

• Earlier implementation of the structural

survivability provisions of SOLAS Chapter XII

(which IACS has accelerated from 15 to 10

years of age with effect from 1 January

2003).

IACS has announced the following five measures

are under development with a target to complete

the requirements in time to give owners sufficient

notice to plan for and implement the

modifications by the due date of the next

Intermediate or Special Survey commenced on

or after January 1, 2003:

• Installation of improved bulwark or

breakwater structure on existing bulk
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carriers when not fitted with a forecastle,

and a forecastle on new vessels to provide

more protection for forward hatches and foredeck fittings;

• Increased integrity of fore-deck fittings on

existing and new bulk carriers to resist

green water loading;

• Implement hatch cover requirements to the

forward 25% length of existing vessels that

are generally equivalent to UR S21

requirements for new vessels;

• Implement requirements for the strength of

side shell frames to existing vessels taking

into consideration IACS UR S12, which

currently is applicable to new bulk carriers;

and

• Fit water ingress detection and alarms for

spaces forward of the cargo area.

MISCELLANEOUS

Safety of Large Passenger Ships

Continuing its effort to undertake a global,

holistic evaluation of potential risks associated

with large passenger ships, the MSC further

refined its objectives and assigned a number of

specific task to its Sub-Committees.

Based on the guiding philosophy that places

emphasis on casualty prevention, improving

survivability of the ship as a safe haven for its

passengers, twelve tasks were assigned to

relevant Sub-Committees, the last three of which

were retained by the MSC:

1) Improve ship survivability against grounding,

collision or flooding;

2) Assess fire protection and prevention

measures (active/passive);

3) Assess emergency evacuation considering

ship survival time and crowd management in

light of any new technologies;

4) Review LSA functional requirements to

develop performance-based standards;

5) Evaluate recovery and rescue techniques

considering capacity of SAR services to

rescue large numbers of passengers;

6) Develop measures to assess alternative

designs to facilitate use of new

technologies;

7) Review ship operations and management

considering safe manning levels,

communication issues and officer/crew

training levels;

8) Assess safety to proceed to port after

fire/flooding by identifying essential systems

and considering redundancy provisions;

9) Review hardware and human element

measures to prevent grounding;

10) Review medical management practices,

equipment, qualifications and staff levels;

11) Improve ship security (underway by MSC);

12) Review measures including food handling

and sanitation relative to health-safety.

One new technology that is currently being

considered under Task 3 is a proposal by the

U.K. to allow the use of directional sound as an

alternative to low location lighting for evacuation.

Placed at discrete locations, trial testing shows

much improved evacuation times in smoke-filled

spaces as the emitting sound was clearly

identified and distinguishable against sound

levels of a fire and one’s own breathing

apparatus. Costs have been estimated to be

20% lower than low location lighting.

There had been a proposal to quantify (at least

nominally) the size of passenger ships (e.g.,

length, tonnage, number of persons) under

consideration by this task. However, the MSC

decided that it would be more appropriate for the

individual Sub Committees to consider size as it

may vary according to the assigned task.

Passenger Ship Evacuation Analysis

To facilitate prompt evacuation by passengers

and crew along escape routes, taking into

account possible congestion that may occur due

to crew movement in an opposite direction and

the possibility that certain escape routes,

assembly stations, embarkation stations or

survival craft may be unavailable as a result of a

casualty, the Committee approved

MSC/Circ.1033 which contains interim

guidelines to assess the adequacy and flexibility

of escape arrangements.

Evacuation time limits are recommended to not

exceed 60min for ro-ro passenger ships and

passenger ships with no more than three main

vertical zones and 80min for all other passenger

ships. Evacuation time, calculated by a

simplified method or by simulation analysis, is

defined as the total time it takes all persons to

travel (calculated in a probabilistic manner) to
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their assigned assembly station plus 2/3 of the

time it takes to embark and launch life boats

(30min.maximum).

Scenarios are assessed for evacuation during

day and night, with different initial distribution of

passengers and crew throughout the ship.

STCW Transitional Period to End

The MSC recalled that IMO’s approved

extension of the 1 February 2002 transitional

period deadline will expire on 31 July 2002. The

MSC also noted that after 31 July, major nonconformities could be raised against a ship and

the Company in cases where the seafarer did

not hold the necessary STCW 95-compliant

certificates or endorsements.

In this regard, Japan informed the Committee

that a concentrated campaign recently

undertaken by the Paris MOU had indicated that

approximately 35% of ships inspected had

deficiencies in seafarers’ certification.

Cargo Securing Strength

The Committee approved MSC/Circ.1026 which

revises the advanced calculation method to

determine the strength of securing

equipment/lashings contained in the Cargo

Securing Code. The new Circular:

• Revises the existing safety factor (1.5) used

to determine the calculated strength of the

device based on the device’s safe working

load (i.e., CS = SWL/1.5). For all

calculations of force and moment a safety

factor of 1.5 is to be used, except for tipping

where 1.35 is to be applied;

• Provides for a more uniform definition of the

horizontal securing angle given that securing

devices do not usually have a pure

longitudinal or transverse direction in the

horizontal plane; and, based on this more

uniform definition,

• Provides expanded tables of force

coefficients as a function of friction and

horizontal securing angles.

Asbestos Monitoring Guidelines

The MSC approved MSC/Circ.1045 which sets

out guidelines for setting up a maintenance and

monitoring program with the principal objective of

minimizing exposure of all crew and passengers

on board to asbestos fibers while the ship is “in

service” as opposed to when the ship is in a

repair or dry dock. The guidelines consider

three scenarios where there may be general

exposure, where more direct exposure in

working areas with a reasonable likelihood of

asbestos/fibers and where asbestos/fibers are

present (except for the three applications in

pumps, fire risk watertight joints and high

temperature flexible couplings permitted by

SOLAS). An inspection and assessment on

board ship by qualified professionals is also

recommended.

Testing of Watertight Doors

The MSC approved an alternative means to test

the watertightness of doors fitted in passenger

ships and cargo ships where testing may cause

possible damage to insulation or outfitting items.

As an alternative to testing by water pressure to

a head up to the bulkhead or freeboard deck

respectively, prototype pressure testing (before

the door is fitted) of each type and size of door

with a test pressure corresponding at least to

the head required for the intended location may

be accepted. Installation and fit-up shall

correspond to that of the prototype test with

each door checked for proper seating. This

regulation II-1/18 is scheduled for adoption at

MSC 79 in December 2004.

Thermal Protection Assessment

The MSC approved MSC/Circ.1046 which

provides information to assist in assessing the

impact of environmental factors, specifically

water temperature on thermal protection

equipment selection in the context of

hypothermia. Based on the criteria that thermal

protective performance for various types of

equipment is defined as the time to reach a

deep body temperature of 350C or reduce a deep

body temperature by 2

0C, where a significant

degree of incapacitation is expected to occur,

the Guidelines provide for comparison purposes

only the following table of relative performance

characteristics for equipment. Thermal Protective Means Lifejacket Thermal Protective Lifejacket Anti-Exposure

suit

Immersion

suit

(UnImmersion

suit

(Insulated)

IMO Minimum Test Requirements
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Time na 2h 1h 1h 1h

Temp - 100C 5

0C 50C 20C

Time for core temp drop of 20C or to 350C

When exposed to water with temps at left

0

0C - 0.5h 1.5h 1.5h 6h

5

0C 0.5 h 0.75h 2h 2h >12h

100C 0.8h 2h 4h 5h >12h

200C 1.7h 2h 10h >12h >12h

Immersion and Anti-exposure Suits

The MSC approved MSC/Circ.1047 which

provides guidance to the crew, when inspecting

immersion suits and anti-exposure suits required

by SOLAS, to check the storage bag’s general

condition and that closures remain satisfactory

for ease of suit removal. The suit, which should

be dry inside and out and free of deterioration,

should correspond to the type and size identified

on the bag. Donning instructions should be

legible and zippers should easily operate.

Inflatable head support and/or buoyancy ring

where fitted should be checked monthly for

damage and inflated quarterly.

ISM Major Non-Conformities

Upon MEPC’s October 2002 anticipated

concurrence with MSC’s approval, additional

ISM guidelines will be issued for certifying

compliance with the ISM Code.

The revision embraces the IACS practice of

allowing a major non-conformity to be

downgraded, provided a corrective action plan is

presented to the auditor prior to completion of

the audit. Such a practice is carried out in lieu

of withdrawing the ISM certificate which, in the

case of a withdrawn DOC, automatically

invalidates the associated SMC’s.

Somewhat different than the current guidelines

(which require an audit equivalent in scope to

that of an initial audit in order to revalidate the

withdrawn certificate) a downgraded major nonconformity can be accepted provided an

additional audit is satisfactorily completed within

a time period not to exceed 3 months. During

this period a short term certificate is issued to

allow for the accumulation of objective evidence

demonstrating the effective functioning of the

SMS with respect to the corrective action

implemented relative to the major nonconformity.

Emergency Towing Arrangements

The Committee approved resolution

MSC.132(75) which clarifies that the emergency

towing arrangements fitted on existing tankers in

accordance with resolution A.535(13) may be

retained provided that the towing arrangements

at one end of the ship are pre-rigged for ready

deployment as per the requirements of the

current Guidelines contained in resolution

MSC.35(63).

HSC Model Test Guidelines

The Committee approved MSC/Circ.1029 which

contains guidelines for the conduct of model

tests for Ro-Ro High Speed Craft (HSC) in the

event that such tests are to be used as a basis

for exemption from the requirement to fit an inner

bow door under the 2000 HSC Code.

The intent of the tests is to demonstrate that the

craft satifies certain residual stability criteria with

accumulated water on the vehicle deck(s) as a

result of failure of the bow shell door. Tests are

required to be carried out for several headings

and durations (which may be successively

accumulated to represent the recommended 10

minutes of full scale operation).

The accumulated water may be determined by

direct measurement at the end of each test or

by calculation from measured relative water level

within the vehicle space.

Tests should be carried out in waves with not

less than two significant heights corresponding

to 100% and 70% of the worst intended

operating conditions using three narrow band

JONSWAP spectra.

FIRE SAFETY

The MSC approved a number of circulars which

contain recommendations and guidance relative

to the application of fire safety regulations

contained in SOLAS and the Fire Test

Procedures (FTP) Code as summarized below.

FTP Code Type Approval

The MSC approved MSC/Circ.1036 which

recommends that type approval certificates for
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windows should indicate which side of the

window was exposed to the heating condition

during the test and cite which of the optional

tests was applied.

The Circular recommends that the minimum

window size tested under resolution A.754(18)

be revised to reflect the maximum size and that

the type of glass pane, its minimum thickness

and gaps, if appropriate, should be

commensurate for which approval is sought.

Test results obtained on this configuration

should, by analogy, allow for extending

approvals to windows of the same type, but with

lesser dimensions or greater thickness.

Smoke Detectors

The MSC approved MSC/Circ.1035 which

recommends that detectors fitted as equivalent

to smoke detectors required by SOLAS should

comply with Chapter 9 of the Fire Safety

Systems Code. This includes requirements for

power supply, performance, location and signal

characteristics. The only exception is where

carbon monoxide detectors are used, in which

case the alarm threshold should be set at 40ppm

with the ability of the detector to be adjusted to

high and low sensitivity settings in order to

obtain the optimum performance and to

minimize false alarms

Smoke Control

The MSC approved MSC/Circ.1034 sets out

guidelines to prevent the entry of smoke from

surrounding spaces into internal assembly

stations in order to permit the assembling of

passengers. For atriums, smoke control and

ventilation systems should be capable of

maintaining visibility in atriums in order to assist

in safe escape and to allow fire-fighters to

operate.

Compliance with the above performance

standard is facilitated by requiring each internal

assembly station and atrium to be served by a

separate ventilation system that is independent

of systems serving other spaces. Relative to the

normal pressure found in surrounding spaces,

the system is to maintain a negative pressure for

the atrium (as this space is not considered an

escape route) and positive pressure for internal

assembly stations (as these spaces form part of

the escape route).

Note - Items in [brackets] refer to the agenda items. For

further information concerning the above information,

please contact ABS Regulatory Affairs Department at:

tel: 201-226-5320; fax: -5314; Email:

gshark@eagle.org
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6 THE NAVAL ARCHITECT JULY/AUGUST 2003

SEVERAL interesting new safety

technologies, including the now commonly

used emergency low-location lighting in

various forms, have resulted from some of the

high-profile marine disasters of the last 26

years. These have particularly arrived since the

Herald of Free Enterprise accident in 1987, but

other important catalysts have included the fire

on Scandinavian Star in 1990, the Estonia

disaster of 1994, and a relatively unpublicised

incident on Nieuw Amsterdam in 2000, in which

electro-luminescent low-location lighting was

called into question. 

Nevertheless, none of the new technologies

can perhaps be considered so revolutionary (yet

perhaps so simple) as a novel one being

promoted today, which uses a human being's

basic sense: sound. Audible alarms are, of

course, in everyday use on board ships, but until

now, none have been specifically harnessed to

improve lifesaving; that situation is however

changing with the introduction by a UK-based

company named Sound Alert Technology of

what is known as directional sound. Its

technique, named Localizer, won the Royal

Institution of Naval Architects' 2002 Safer Ship

Competition.

Localizer, designed to help guide people to

exits in the dark but, perhaps more importantly,

under smoke conditions when exit and sign

visibility is severely restricted, evolved from a

chance incident that Professor Deborah

Withington, a sound specialist at Leeds

University, in the UK, experienced. While in a

taxi, she heard a police or ambulance siren but

realised that she could not identify the direction

from which it came, due to the frequency used

in such equipment.

The resulting technology (which was the

subject of papers earlier this year at The Royal

Institution of Naval Architects' Passenger Ship

Safety conference and at the Warship 2003:

Airpower at Sea conference*) instead uses

broad-band, multi-frequency sound that is

easily and quickly located by the human ear.

All current alarms sound in the range between

1kHz and 2.5kHz because the human brain is

very sensitive to these levels; unfortunately, no

directional information is given at these

frequencies, so a new spectral cue is required,

hence the term broad band (frequencies from

20Hz to 20,000Hz). The special sound

technique developed by Sound Alert

Technology has been patented. Directional

sound is already being introduced on land and is

being considered for aircraft.

IMO's concerns over the new generation of

very large passenger liners led to a UK working

party being set up (Maurice Storey and Alan

Cubbin from the Maritime & Coastguard

Agency, John Rugg, from Lloyd's Register, and

John McNeece, formerly with the McNeece

design consultancy). They considered sound to

be a positive aid for evacuating public spaces

and accommodation, and were optimistic over

its future - and brought it to the attention of their

IMO colleagues on the Large Passenger Ship

Safety working group of the MSC.

Subsequent marine trials appear to have

proved that sound is much more effective in

guiding passengers to exits than photoluminescent and electro-luminescent lightbased systems. It is especially interesting to

record that even technical staff intimately

familiar with cabin arrangements on particular

ships became totally disorientated in escape

trials under smoke conditions.

A further driver for sound-based systems has

been the very poor survivability time for

humans in heavy toxic smoke - as little as

1.5min, according to some researchers. Indeed,

90sec is used by the aircraft industry as the

measure of an aircraft's ability to quickly

evacuate passengers. 

Localizer beacons at strategic exit positions

could be especially useful, believes Sound Alert

Technology, in the large restaurants, casinos,

and lounges that tend to characterise the modern

generation of giant cruise liner and where

escape points could be very difficult to find

under smoke conditions. Under current SOLAS

regulations, low-location lighting is not needed

in such rooms - perhaps regrettably considering

the large numbers of people congregating in

them - but if it were to be made mandatory here,

some believe that it would be ineffective, given

the size of such spaces.

The UK MCA has taken a leading role in

promoting sound technology, and a most

interesting series of trials - devised in

conjunction with Leeds University and the

University of Strathclyde were carried out in

June and October 2001. These took place, with

the assistance of Tom McNeil, technical

Directional sound: an important new escape aid

Some figures and diagrams compiled by the UK MCA, which illustrate the attractions of directional

sound in speeding escape from various parts of a ship.

* 'Directional sound evacuation - an improved system for

way guidance from open spaces and exit routes on ships',

by Prof Deborah Withington, School of Biomedical

Sciences, University of Leeds, and Mike Lunch, Sound

Alert Technology Plc. Presented at RINA headquarters,

London, at The Royal Institution of Naval Architects'

international conference on Passenger Ship Safety, March

25-26, 2003, and also at the Warship 2003 conference on

June 25-26, 2003.
WITH recent increases in ship speed and

propeller loading, there is increased

danger of cavitation on the propeller and on

appendages such as rudders, pods, and struts.

The German model basin HSVA recently

conducted several full-scale observations on

semi-balanced rudders, revealing quite

dramatic cavitation occurrences and

cavitation-induced erosion damage.

Rudder cavitation erosion is of concern if it

occurs within the range of rudder angles a=±5

deg while course-keeping. Different types of

cavitation occurr on rudders, such as bubble,

sole, gap, vortex cavitation, and cavitation

caused by surface irregularities. HSVA

believes that principal emphasis must be

given to the area around the pintle. There,

details of gap size and geometry, as well as

exact workmanship, are of paramount

importance.

Model tests

Model tests can help in the early stage of

design, especially when they are performed in

a sophisticated test facility, and with a special

aim to predict those types of cavitation

occurrences. Rudder cavitation is not only

influenced by the geometry of the rudder, but

also by the inflow to the rudder and propeller.

Therefore, tests in 3D inflow, behind the

whole ship model, to give full propeller/hull

interaction, are necessary to obtain a clear

view of cavitation behaviour. If the danger of

cavitation-induced erosion is large for

specific areas such as the pintle, additional

tests in a smaller tunnel with even higher

Reynolds numbers are recommended.

For the scenario mentioned above, part of a

large rudder model was tested in HSVA's

large cavitation tunnel. These tests could

prove that there are mainly two critical areas

where cavitation occurs: the gaps between the

moveable part and the fixed part, and the

areas downstream of the maximum thickness

of the rudder sections. On the part-rudder

model, complicated interactions between the

flow through the gaps and the cavitation

phenomena were observed.

One solution to improve cavitation

behaviour is to keep cavitation - which cannot

be avoided - away from the rudder surface in

order to avoid erosion damage at those points,

which are sensitive with respect to strength.

To achieve this, use was made of wedgeshaped spoilers. The final rudder exhibits the

following modifications (compared with the

original rudder):

• width alteration of the horizontal gaps and

lower vertical gap in order to obstruct flow

through gaps

• spoiler at the lower end of the upper

vertical gap (upstream of medium

horizontal gap)

• spoiler on the lower pintle, in order to

direct cloud cavitation away from the

rudder surface

• fitting of a horizontal plate below the lower

horizontal gap, extending downstream of

the lower vertical gap.

These modified rudders have been in use on

two ships for six months, and diver reports show

an improvement regarding observed erosion

damage.

Numerical investigations

Before model tests, CFD calculations can be used

to check cavitation behaviour of different rudder

designs. With simple potential theoretical

techniques, pressure distributions can be

determined for the rudder profiles. Thickening

was observed - often used because of strength

considerations - which leads to significant lowpressure drops in the region of the pintle bearing.

This is the most critical area of the rudder, and

3D viscous-flow calculations reveal complicated

flow behaviour in this region. The water is

sucked in, comparable to the behaviour of a

scoop, into the gap between rudder horn and

rudder blade. By a change of geometry in front of

the gap, the quantity of water passing through

the gap could be reduced, resulting in

improved pressure distribution and therefore

less cavitation danger.

director of Caledonian MacBrayne, onboard

two CalMac moored ferries (at-sea trials were

not possible due to insurance restrictions). A

total of 360 volunteers from local towns were

recruited (all ages from 17-67), including blind

and deaf people, and of both genders) to test

Sound Alert Technology's system using

theatrical smoke.

Apparently, real smoke with its toxic gas

causes reflex closing of the eyes and is eyewatering, thus making escape even more

difficult for passengers. Water-mist fire

extinguishing systems - efficient though they

are - also have a side-effect of making smoke

fall to the deck quicker thus making public

space exit even more hazardous. The CalMac

ferry trials also included tests with electroluminescent low-location light-based systems.

A second series of tests was also carried out in

October last year at one of the Fincantieri

shipyards on a new Carnival cruise liner,

Carnival Conquest, shortly before delivery.

For one of these, the nine-deck-high atrium was

filled with smoke, and directional-sound alarms

fitted to all 26 exits (20 of which were on the

lower three levels, which created a confusing

acoustic scenario). Apparently, volunteers

found suitable exits very quickly.

For a cabin test in the complex crew area on

the same ship, directional sound gave 55%

reductions in average escape times when

compared with low-location lighting. The

public address and general alarm systems

were operated in both sets of test but had no

impact on the sound system's effectiveness.

The MCA appears to be impressed with such

figures, given the limitations of trials

scenarios; it is particularly interesting to note

that this organisation records that low-location

lighting was little used in the trials 'since in

3% density smoke, lighting assistance was not

visible.'

One piece of legislation that may hasten the

introduction of directional sound is the US

Americans with Disabilities Act, which now

applies to passenger ships; since blind people

cannot see low-location lighting, directional

sound would be a highly desirable feature.

Meanwhile, last year, both the UK and

German marine administrations have formally

proposed directional sound evacuation to IMO

as an equivalent to low-location lighting

within SOLAS regulations. It is believed that

Italy also supports the technology in principle.

Unfortunately, as most readers will know,

the wheels of IMO turn exceedingly slowly

and it could be several years for this

equipment to be formally approved.

Nevertheless, according to Sound Alert

Technology, directional sound could still be

introduced, using the provisions of SOLAS 2-

II, Regulation 17; this allows for 'alternative

design and arrangements' to be examined and

approved, subject to fire safety engineering

and risk analysis. However, some work by

owners and yards would be needed. 

Installation of a sound system could be very

attractive to shipyards - it is much simpler than

a low-location lighting design (some versions of

the latter are understood to be very labourintensive to fit due to the many short sections,

each of which must be wired from both ends for

redundancy). It could readily be integrated

within a public address or general alarm circuit

using established SOLAS practice, using a

second loop for redundancy in each fire zone

and additional sets of loudspeakers. New

direct-addressable digital technology for such

circuits could also be included. An alternative is

a free-standing arrangement, but this would

have to go through a lengthy approval process. 

A performance-based specification for

directional sounders has recently been

published by the British Standards Institution

(PAS41:2003). Notwithstanding all this

optimism, it seems likely at the present time that

few operators will be bold enough to install the

new technology prior to formal IMO approval -

except perhaps to meet their obligations under

disabilities legislation.

THE NAVAL ARCHITECT JULY/AUGUST 2003 7

Reducing rudder erosion on fast ships

These diagrams illustrate an improved pressure

distribution, thus less cavitation danger due to a

change in rudder geometry.
A P P L I C A T I O N S G U I D E

Directional Sounder

with Voice Messaging
1

A P P L I C A T I O N S G U I D E

Directional Sounder

with Voice Messaging

Contents

Section 1: Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Shortcomings of Traditional Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Directional Sound Aids Evacuation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Directional Sound Influences Human Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Voice Messaging Aids in Guiding Occupants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Section 2: Why Directional Sound Works. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Psychoacoustic Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Acoustic Performance in Building Applications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Bandwidth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Sound Level Masking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Average Ambient Sound. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Compatibility with Traditional Fire Alarm Notification Appliances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Compatibility with Voice Evacuation Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Reverberant Building Environments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Section 3: Applicability of Building Codes and Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Section 4: Locations for Directional Sounders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

What are the exits where directional sounders can be used?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

What are the areas of refuge or areas of rescue assistance where directional sounders can be used?. . . . . . . . . . . . . . . . . . . . . 8

What are other means of egress components where directional sounders can be used?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Locations that may not be suitable for directional sounders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Section 5: Directional Sound Installations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Type 1 (Basic) Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Type 2 (Enhanced) Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Special Considerations for Dead-Ends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Section 6: Positioning Directional Sounders on Wall and Ceiling Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Section 7: Frequently Asked Questions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Section 8: Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

List of Illustrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

This application guide provides information to building design professionals, 

specifying engineers, fire alarm system installers, and 

enforcement authorities regarding 1) the technical or psychoacoustic basis for directional sound technology, and 2) 

the implementation of directional sounders as an aid to 

locating exits, egress routes or refuge areas.

Directional sounders, integrated with the building’s fire 

alarm system, are a supplemental, audible means of identifying exits and egress routes and can provide a means of 

overcoming the limitations of current exit signage and alarm 

signals. The directional sound from the devices does not 

conflict with the traditional audible alarm signals, whether 

horns or bells; however, they are not a substitute for these 

traditional fire alarm devices. (Directional sounders are 

NOT intended to replace or be a substitute for fire alarm 

system notification appliances.) There may be potential 

compatibility issues with the voice speakers for which guidance is provided in the following sections of the guide.

Shortcomings of Traditional Methods

Fire alarm systems designed to initiate evacuation or relocation of occupants use audible and visible notification 

appliances that occupants will hear or see when the fire 

alarm system operates. Depending on the particular fire 

emergency plan, the occupants may be required to evacuate or relocate immediately or prepare for such evacuation 

or relocation. Oftentimes, occupants may not be familiar 

with the building and its associated emergency egress 

routes and may have to rely on exit maps, markings, or 

signage to guide them to an exit, refuge area or other 

means of egress.

The traditional maps, markings and signage required by 

codes provide occupants a visible means for locating or 

finding a path to safety. Generally, exit signage will be the 

primary means for locating an exit, refuge area or other 

means of egress. If an emergency plan has been prepared, 

it may include diagrams showing the locations and routes to 

exits. Occupants, however, may not have had an opportunity 

to study and understand such a diagram or cannot visualize 

an actual escape route as depicted on such a diagram.

There are other limitations to the way building occupants 

identify the means to reach a point of safety in a building 

during a fire or other emergency that necessitates evacuation or relocation. Persons with visual disabilities will have 

difficulty with emergency information that relies on visual 

cues. The signals that alert the occupants to an emergency 

event and suggest the need to evacuate usually are both 

audible and visual. Illuminated exit signs serve only as 

a visual cue. Other weaknesses are that the illuminated 

front of exit signs may often compete with nearby bright 

lights or other visually distracting elements. Exit signs may 

be inadvertently blocked from view due to renovations 

or remodeling of building or tenant spaces. Of course, at 

the time of a fire, when exit signs are most needed, it is 

possible for smoke to obscure exit signs and the location 

of exit doors.

Directional Sound Aids Evacuation

Directional sound technology offers a solution to improve 

the exit or relocation situation for building occupants. To 

help occupants in finding their way to an exit, refuge area 

or other means of egress, directional sounders integrated 

with the fire alarm system provide additional auditory 

information that can assist or aid occupants in locating 

escape routes without conflicting with the traditional 

fire alarm system notification appliances such as bells or 

horns. Directional sounders utilize a broadband acoustic 

characteristic that is distinctive from the audible sounds 

of bells, horns, or voice speakers. Directional sounders are 

intended to operate simultaneously with the traditional fire 

alarm notification devices and to be wired as part of the fire 

alarm system notification circuits. Again, it is important to 

note that directional sounders are NOT intended to replace 

or be a substitute for notification appliances required by 

building or fire codes. They are, however, to be installed 

on the notification appliance circuits, in accordance with 

NFPA 72, National Fire Alarm Code.

Experts and researchers in the area of human behavior 

have recognized two phenomena that appear common in 

evacuations of buildings.1,2,3 First, is that occupants tend to 

exit a building by the route familiar to them, which may 

be the same route they used to enter a building. Second is 

the concept of “learned irrelevance” of exit signs, where 

people continually exposed to exit signage seldom consider 

Section 1

Introduction

Preface

This installation guide is the first effort of System Sensor to address the application of its new directional sounders for 

buildings and structures. The technology and initial applications of directional sound were developed at the University of 

Leeds under the supervision of Professor Deborah Withington and have become an accepted technology by international 

organizations as an aid to evacuation. While directional sound technology is a recognized and accepted technology overseas, System Sensor considered it important and appropriate to obtain North American expertise to review the technology 

and assist with the development of this application guide. Experts with backgrounds in acoustic engineering, human 

behavior during fire and evacuations, building and fire codes; and fire protection engineering were key to this effort.

This guide intends to promote an understanding and awareness of the benefits and capabilities of directional sound. A 

primary focus of this guide is to provide information important to building design professionals, specifying engineers, fire 

alarm system installers, and enforcement authorities that will increase the probability of a proper installation and reduce 

the possibility of misapplication of directional sounders in the commercial marketplace. As with any new technology, it 

is anticipated that the role directional sound will play as a safety enhancement in buildings and structures will continue 

to develop and that this installation guide will be revised and updated to reflect modifications or improvements of the 

product features and refinements in directional sound applications in coming years.

February 2007

2

To support the development 

effort for this guide and other 

work, Schirmer Engineering 

Corporation, serving as 

the lead fire engineering 

consultant, assembled a team 

of experts that included both 

in-house staff and several 

key individuals recognized for 

their particular expertise in 

the areas of human behavior, 

fire protection engineering, 

and design of acoustic 

environments. A special 

thanks to the following for 

their contributions to date: 

 

John L. Bryan, DEd., Professor 

Emeritus, Department of 

Fire Protection Engineering, 

University of Maryland, and 

a student and observer of 

human behavior in fire.

Guylene Proulx, Ph.D., Senior 

Scientist, National Research 

Council of Canada, and an 

international expert on human 

behavior in fires.

Robert P. Elfering, P.E., an 

acoustical engineer with 

Shiner & Associates, a 

nationally recognized firm 

specializing in acoustics for 

commercial, multi-family, 

residential, institutional, 

educational, industrial and 

recreational facilities.

Daniel J. O’Connor, P.E., fire 

protection engineer. VicePresident of Engineering for 

Schirmer Engineering and the 

Chair of the Society of Fire 

Protection Engineer’s Task 

Group on Human Behavior. 

Member of the NFPA 72 

Committee on Initiating 

Devices. 

The work of these individuals 

serves not as an endorsement 

of the technology, but 

as independent sources 

for validation of the 

appropriateness of directional 

sound and the identification of 

limitations and considerations 

in application.
S Y S T E M S E N S O R

the information it is intended to convey, i.e. the identification of alternative exits and exit access. In an emergency, 

they fail to respond to signage pointing to alternate means 

of egress, instead opting for the exits with which they are 

familiar.

Directional sound offers a means for reducing these tendencies and providing an additional stimulus in the form 

of sound cues that draw attention to otherwise ignored 

egress routes and exit locations. In this way, directional 

sound can serve to increase exit utilization by encouraging 

the use of all exit facilities and speeding total evacuation 

when needed.

Directional Sound Influences Human Behavior

The broadband sound pulses of directional sounders make 

use of our natural ability to localize sound sources when 

provided with the appropriate spectral and temporal cues. 

To be of benefit, the technology requires occupants to 

make use of these supplemental audible cues in a manner that enhances their behavior during an evacuation. 

The psychoacoustic response to directional sounders has 

been shown in numerous exercises and research studies to 

lessen the time required for evacuation and to effectively 

assist occupants searching for egress routes and exits. 

Numerous research studies have shown that directional 

sounders improve the flow of people towards exits, and 

they improve evacuation efficiency. While many of these 

realistic exercises were conducted on passenger ships and 

ferries, the results are broadly applicable to evacuation and 

relocation scenarios in buildings.

Prompted by a 1990 fire that resulted in 158 deaths 

aboard the Scandinavian Star ferry in Norwegian waters, 

numerous evacuation trials have been conducted by the 

University of Leeds and the University of Strathclyde 

between 2000-2003. The various trials involved numerous 

scenarios such as evacuations with and without directional 

sound, evacuations with low visibility conditions created 

by use of theatrical smoke, and a variety of room and 

complex corridor arrangements. In smoke-filled scenarios 

with little or no visibility of exit signs, directional sound 

demonstrated its benefit to provide cues that significantly 

reduced the time for subjects to find the nearest exit and 

to find the exits without retracing their steps. 

The egress behavior of subjects in normal visibility did 

not show the same extent of improvement in egress times, 

but subjects indicated the sound cue as a confirming aid 

in finding the exit. A more dramatic result was evident in 

evacuation trials when subjects received a briefing on the 

meaning of the directional sound. In these trials with briefings, the subjects consistently performed better at finding 

the closest exit and exhibited faster exit times. 

Voice Messaging Aids in Guiding Occupants

A question often asked about directional sounders is how 

building occupants will know how to react when they hear 

the sound. Although the sound is intuitive to many people, an enhancement made to directional sound technology 

is the addition of voice messaging. In between four second 

bursts of directional sound, an alert message in the form 

of a recorded voice message can be used. The purpose 

of the voice message is to instruct the occupants of what 

action to take as they approach the directional sounder. 

This messaging will allow them to react quickly and confidently without training or prior knowledge of directional 

sound. The messages will instruct occupants that they are 

approaching stairs going up, stairs going down, an area of 

refuge, or the exit. 

3
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

Today, there is a significant body of literature and 

texts regarding the human 

mechanism of hearing and 

the science of acoustics. Since approximately the 1980’s 

significant studies and technical work have been done to 

quantify and further understand the psychoacoustic mechanisms that allow the human ear to pinpoint or localize the 

source of sounds.4,5,6,7 The following section summarizes 

the psychoacoustic basis for sound localization, describes 

why directional sound works and why directional sound is 

compatible with traditional fire alarm signals and reverberant building environments.

Psychoacoustic Theory

The ability to pinpoint the location of a sound source is 

based on the physics of sound and the physiology of the 

human hearing mechanism. The brain processes a large 

amount of neural signals, some of which provide cues to 

the sound source’s location.

People are able to hear sound ranging from about 20 Hz to 

20,000 Hz, although as we age this range diminishes. Many 

fire alarm signals are pure tones or narrowband sound 

in the 1000 Hz to 3000 Hz 

range, to which the human 

ear is particularly sensitive as far as loudness is 

concerned. Unfortunately, 

pure tones in this frequency 

range provide only limited 

localization information.

The primary localization 

cues are provided by interaural time differences (lower 

frequencies), interaural 

intensity differences (mid to 

higher frequencies), and the 

head-related transfer function (higher frequencies). In 

enclosed spaces that may be 

somewhat reverberant, the 

precedence effect provides 

directional information. 

Each of these four psychoacoustic phenomena is discussed briefly below:

The interaural time difference (ITD) and interaural intensity difference 

(IID) are termed binaural 

cues because they depend 

on both ears separated by 

the width of the head. At 

lower frequencies (longer 

wavelength) the time delay 

between arriving sound signals is detectable. Interaural 

time difference is most evident in frequencies below 

about 1000 Hz with clicks 

or short bursts of sound. At 

higher frequencies (shorter 

wavelength) the loudness/intensity differences between the 

ears is more noticeable because of partial shielding of the 

more distant ear by the head. Interaural intensity differences 

are most evident for frequencies above 3000 Hz. Figure 1 

depicts the binaural cues – ITD and IID.

The head-related transfer function (HRTF) relies on the 

effect of the external ear on perceived sound. The HRTF 

describes the transforming effect of the head, torso and 

external ear on sound as it travels from the sound source 

to the ear canals. The shape of the ear attenuates some 

frequencies and amplifies others, filtering the sound field 

as depicted in Figure 2. This filtering effect is mainly due 

to directional reflection effects the pinna and concha of 

the outer ear have on the incident sound field. The HRTF 

changes depending on sound source location, providing an additional localization cue. HRTF operates over a 

range of frequencies, but seems to be most effective in the 

5,000 Hz to 10,000 Hz range. Combined with the listener’s 

head motion, HRTF provides an independent localization 

method to complement ITD and IID capabilities.

In addition to confirming ITD and IID localization cues, 

the HRTF provides vital localization information when the 

sound source is near the plane equidistant from each ear, 

i.e. directly in front, behind or above the head. In these 

situations ITD and IID do not provide distinct localization 

cues because each ear is equidistant and unshielded from 

the source. Front-back and vertical localization of the 

sound source is made possible by the HRTF.

The precedence effect is important for discriminating 

between the direct sound signal and reflected sound, a 

common situation within buildings. The ear is capable 

of discerning and fixating on the first sound received 

(line-of-sight direct signal) and disregarding later signals 

(reflected sound). The acoustical signal arriving first at the 

ears suppresses the ability to hear other signals (including 

reverberation) that arrive up to about 40 milliseconds after 

the initial signal.

All of the above cues are utilized simultaneously when the 

source signal is broadband sound containing a range of low 

and high frequencies. The combination of different cues 

provides reinforcement and redundancy of information to 

enhance the ability to locate the sound source. Broadband 

sound tends to eliminate potential ambiguities that occur 

for pure tone or narrowband sound sources.

For further information regarding the theoretical aspects of 

sound localization, see the list of sources in the enclosed 

reference section.

Acoustic Performance in Building Applications

The directional sound device enables ready localization 

by providing bursts of broadband sound rather than a 

traditional pure tone signal. Intended to be used as a 

supplement to traditional alarm signals, a directional 

sounder provides an additional guidance cue. Parameters 

that account for the performance of directional sounders in 

buildings are as follows:

Bandwidth

Bursts of directional sound cover a broad enough range 

to enable binaural localization cues and HRTF localizaSection 2

Why Directional 

Sound Works

Figure 1. Interaural time and intensity differences of sound.

Figure 2. Examples of frequency dependent attenuation for sources 

in front, above and behind the listener.

4
S Y S T E M S E N S O R

tion cues. A low frequency content enables easy detection 

of interaural time differences, while a medium to high 

frequency content facilitates discrimination of interaural 

intensity differences. Low to high frequency content facilitates discrimination using the HRTF.

Directional sounders contain frequency content extending over almost all of the entire range discernible by the 

human ear. This wide band type of frequency content is 

often referred to as “white noise”. This wide spectral range 

of broadband sound is important for providing redundancy 

and reinforcement of perceived sound signals, enabling 

localization cues due to all binaural, transfer function, and 

precedence effect mechanisms. 

Sound Level Masking 

The concept of “masking” is important when determining appropriate sound pressure levels for alarm signals. 

Masking is an acoustic process in which the audibility 

of one sound (the signal) is affected by the presence of 

another sound (the masking sound). Masking sound, if 

it is loud enough and has similar frequency content, can 

partially or totally hide the signal sound.

Typical building environments have background noise due 

to ventilation and other mechanical systems, telephones, 

conversation, etc. In order to be clearly audible, the sound 

level of alarm signals should exceed background noise levels by at least 10 dB, preferably by 15 dB. The higher alarm 

signal level is required so that it is not hidden (masked) by 

other naturally occurring sound sources.

Average Ambient Sound

Ambient sound levels should be determined in order that 

the sound levels of directional sounders can be set at 

appropriate sound levels. Figure 3 from Appendix A to 

NFPA’s Fire Alarm Code shows examples of what average 

ambient sound levels may be for different applications.8

The examples should not be used as a substitute to taking 

actual on-site measurements. In the same appendix, the 

following is stated regarding the measurement of average 

ambient sound:

“When surveying the ambient sound levels to establish 

the increased level at which a notification appliance 

will properly function, the sound source needs to be 

averaged over a longer period of time. Moderately 

priced sound level meters have such a function, 

usually called ‘Leq’ or ‘equivalent sound level.’ For 

example, an Leq of speech in a quiet room would cause 

the meter movement to rise gradually to a peak reading 

and slowly fall well after the speech is over.

 “Leq readings can be misapplied in situations where 

the background ambient noises vary greatly during a 

24-hour period. Leq measurements should be taken over 

the period of occupancy.”9

Compatibility with Traditional Fire Alarm Notification 

Appliances

Directional sounders are envisioned as an additional 

evacuation aid to be used with, not as a replacement for, 

traditional notification appliances (bells, horns and speakers). Hence, during the period that people are exiting or 

relocating, there will be two dominant alarm system sound 

sources, both of which should be audible. 

Since both traditional alarms 

and directional sounders can 

comfortably exceed most 

common background noises, masking of alarm signals 

by ambient noise is not normally an issue. Traditional 

alarm devices have a strong 

tonal content as opposed 

to the more even, broadband content of a directional 

sounder. 

Figure 4 compares the 

spectrum of a typical fire 

alarm signal at a high setting with the spectrum of 

the directional sounder at 

a lower power setting. Note 

that while the typical alarm 

signal clearly dominates at 

3000 Hz and to a lesser 

extent at upper harmonics, the broadband directional signal of the directional sounder is 20-30 dB 

louder than the fire alarm 

over most of the range. And 

although the fire alarm may 

have an overall A-weighted 

sound level 20 dBA or more 

higher than the overall Aweighted sound level of 

the directional signal, both 

alarms are audible.

The reason that the directional signal does not actually have to be higher in 

overall sound pressure level 

than the traditional alarm 

signal is because the traditional alarm will only mask a 

narrow range of frequencies near the traditional alarm’s 

dominant pure tones. Since the directional sounder has a 

wide spectral range and is generated in short sound bursts 

giving timing, intensity and HRTF cues, most of the broadband sound will be audible in the presence of higher pure 

tone sound levels.

Reverberant Building Environments

Due to the precedence effect, the ear can discriminate 

the direct sound signal from reflected signals in enclosed 

spaces.

The directional sounder’s pulsing broadband directional 

signal makes good use of the precedence effect and can 

compensate for less than optimum listening conditions. 

Even in highly reverberant spaces, in which every surface 

was sound reflective, test subjects have had no problem 

determining the location of directional sounders.

Most building interiors have a blend of sound reflective 

and sound absorbent finishes. However, even under the 

semi-reverberant conditions of certain building interiors 

such as gymnasiums and lobbies finished in concrete 

Location Average Ambient 

Sound Level

Business occupancies 55 dBA

Educational occupancies 45 dBA

Industrial occupancies 80 dBA

Institutional occupancies 50 dBA

Mercantile occupancies 40 dBA

Piers and water-surrounded structures 40 dBA

Places of assembly 55 dBA

Residential occupancies 35 dBA

Storage occupancies 30 dBA

Thoroughfares, high density urban 70 dBA

Thoroughfares, medium density urban 55 dBA

Thoroughfares, rural and suburban 40 dBA

Tower occupancies 35 dBA

Underground structures and windowless 

buildings

40 dBA

Vehicles and vessels 50 dBA

 

Figure 3. Typical ambient sound levels

5

Figure 4. Frequency response of traditional fire alarm signals versus 

directional sounder

3 kHz Fire Alarm

Directional Sounder 

Directional Sounder vs. Fire Alarm Signal Directional sounder at 66dBA and fire alarm horn at 86dBA

measured at 10 feet horizontally in an anechoic chamber

Frequency (Hz)
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

1

Because directional sounders are wired as part of a 

building’s fire alarm system, the codes and standards applying to fire alarm 

installations also apply to directional sound. This is the 

case both when directional sound is added to existing fire 

alarm systems or when it is incorporated into new installations. When an existing fire alarm system is altered to 

incorporate directional sound, it may be necessary to make 

other alterations or replacements so as to have the system 

conform to current standards. 

The application of directional sound requires a basic 

understanding and knowledge of the means of egress, 

means of escape and area of refuge provisions found 

in the model codes for buildings and life safety. There 

are two independent organizations in the United States, 

the National Fire Protection Association (NFPA) and the 

International Code Council, Inc. (ICC), that write model 

building and fire codes intended for legal adoption by local 

governments (cities, counties, states). Local jurisdictions 

may adopt these model codes without change or alter them 

to suit their preferences. Some cities write their own codes, 

and many jurisdictions may still be operating under model 

codes promulgated by ICC predecessor organizations. The 

local authority having jurisdiction (AHJ) should be consulted for information on specific local regulations.

National Fire Protection Association (NFPA)

Batterymarch Park, Quincy, Massachusetts 02169-7471

block, terrazzo, drywall, glass, etc., the sounder’s directional signal will be easily locatable.

Compatibility with Voice Evacuation Systems

Where directional sounders and voice evacuation systems 

employing speakers are utilized within the same occupancy the directional sounders can reduce the speech 

intelligibility of the voice speakers. For this reason it is 

recommended that when both systems are utilized in the 

same installation that the two systems are not operated 

simultaneously. Where simultaneous operation of the voice 

evacuation speakers and the directional sounders cannot 

be avoided there are system design guidelines that can be 

followed to reduce the effects of the directional sounders 

on the intelligibility of the voice speakers.

The factors influencing the loss to speech intelligibility 

include; the intelligibility of the voice system without the 

directional sounders operating, the amount of reverberation present, and the sound pressure differential of the 

directional sounders vs. the voice speakers. 

In general, if the speech intelligibility of the voice evacuation 

system before adding directional sounders is very good then 

the effects of the directional sounders will be minimized. 

Thus, improving the speech intelligibility of the voice system will minimize the loss from the directional sounders. 

This can be accomplished by using high quality speakers, 

using more speakers, and/or increasing the sound pressure 

of the voice system relative to ambient sound levels.

6

High degrees of reverberation will result in greater loss to 

intelligibility of voice systems when directional sounders 

are present. The degree of reverberation of a space will 

depend on the room characteristics such as the volume, 

the nature of finishes and furnishings and the number of 

occupants. Spaces with acoustically soft surface materials 

(textured ceiling tiles, drapes, carpet) will absorb sound 

and be less of a reverberant environment than spaces with 

acoustically hard surfaces (concrete, plaster, glass) which 

reflect sound around a space. To minimize the effects of the 

directional sounders, avoid using directional sounders in 

acoustically hard environments or reduce the sound pressure of the directional sounders in these areas. Sound pressure of the directional sounders can be reduced by either 

reducing the power setting of the sounders in the area or 

carefully selecting the locations of the directional sounders 

to increase the separation of the directional sounders and 

reverberant areas. If the reverberation in an area is too 

great it will not be possible to achieve good speech intelligibility even without the directional sounders.

In locations where the sound pressure of the voice system 

is comparable to the sound pressure of the directional 

sounders the reduction of intelligibility will be increased. 

In general, this will only occur in close proximity to the 

directional sounders. Speech intelligibility can be improved 

by adding additional speakers to these locations. This will 

increase the sound pressure of the voice system in these 

areas. In general, adding a second speaker will result in an 

increase of 3dB. 

Section 3

Applicability of 

Building Codes And 

Standards

NFPA publishes codes and standards concerning all areas of 

fire protection. The key documents published by NFPA that 

define the requirements for exits and refuge areas are: 

NFPA 101, Life Safety Code – NFPA 101 specifies the 

requirements for means of egress, means of escape and 

areas of refuge for new and existing buildings depending 

on the occupancy classification of a building or portion of 

a building.

NFPA 5000, Building Construction and Safety Code – NFPA 

5000 is model building code for new construction that 

specifies the requirements for exits and refuge areas based 

on the occupancy classification of a building or portion of 

a building.

NFPA 1, Uniform Fire Code – NFPA 1 is a fire prevention 

code that incorporates provisions from prior editions of 

NFPA 1 and provisions of Western Fire Chiefs Association 

Uniform Fire Code. The document contains provisions for 

the means of egress and means of escape for new and 

existing buildings consistent with NFPA 101.

NFPA various other documents – Other NFPA documents 

may contain specific requirements for means of egress and 

means of escape.

Two other NFPA documents are of particular interest in 

relation to directional sounder installations:

NFPA 70, National Electrical Code – This is one of NFPA’s 

most widely recognized documents, covering all aspects of 
S Y S T E M S E N S O R

electric wiring installations, including those for fire alarm 

systems. It has been adopted by ICC (see below) as part of 

its series of codes.

NFPA 72, National Fire Alarm Code – NFPA 72 covers 

all aspects of fire alarm installations, including detection 

devices, manual fire alarm stations, alarm notification 

devices, central station services, power supplies and 

arrangement of circuits. It has been adopted by ICC (see 

below) as part of its series of codes. The 2007 Edition of 

NFPA 72 provides guidance on installing and maintaining 

directional sounders in Chapters 6 (Protected Premises), 

Chapter 7 (Notification Appliances) and Chapter 10 (Testing 

and Maintenance.)

International Code Council, Inc. (ICC)

5360 Workman Mill Road

Whittier, California 90601-2298

The ICC is the successor organization to the three regional 

model code development organizations:

Building Officials and Code Administrators (BOCA)

International Conference of Building Officials (ICBO)

Southern Building Code Congress International (SBCCI)

The ICC was formed for the purpose of combining the 

above three organization’s codes into a single set of model 

building and fire codes. The first combined documents 

included the ICC’s 2000 International Building Code and 

2000 International Fire Code, which define requirements 

for exits and refuge areas. Many jurisdictions have or are in 

the process of adopting the ICC’s building and fire codes, 

however, the BOCA National Building Code, the ICBO 

Uniform Building Code, and the SBCCI Standard Building 

Code continue to be used in many jurisdictions.

ICC documents that may contain exiting provisions or that 

may affect fire alarm (and directional sounder) installations include:

• International Building Code

• International Fire Code

• International Existing Building Code

• International Residential Code for One- and TwoFamily Dwellings

• International Property Maintenance Code

• ICC Electrical Code – Administrative Provisions (adopts 

by reference NFPA 70)

• International Performance Code for Buildings and 

Facilities

Federal Accessibility Laws:

Americans with Disabilities Act Accessibility 

Guidelines (ADAAG)

Fair Housing Accessibility Guidelines (FHAG)

In addition to any NFPA or ICC documents that may 

be legally adopted and applicable to building design 

are the Federal requirements applicable to buildings. 

The Americans with Disabilities Act (ADA) and the Fair 

Housing Amendment Act (FHA) are federal regulations 

that affect building construction as it relates to accessibility for persons with disabilities. Exit design, refuge area 

design and fire alarm system design all are impacted by 

these federal laws.

Currently, NFPA and ICC documents address accessibility 

provisions for people with disabilities which are modeled 

on the requirements of the Americans with Disabilities Act 

Accessibility Guidelines (ADAAG) and the Fair Housing 

Accessibility Guidelines (FHAG). Compliance with NFPA 

or ICC documents, however, does not constitute compliance with federal requirements and designers are guided 

to review and understand both ADAAG and FHAG requirements as they may apply to exit design, refuge area design 

and fire alarm system design. Additionally, it is noted that 

in the case of public service facilities (Title II of the ADA) 

an alternative design standard can be applied in lieu of the 

ADAAG. This standard is the Uniform Federal Accessibility 

Standards (UFAS).

Underwriters Laboratories, Inc. (UL)

UL is a testing laboratory that evaluates components 

of fire alarm systems to verify compliance with NFPA 

requirements and their own standards. Equipment such as 

directional sounders that pass UL tests are identified by a 

label or listing. UL publishes an annual directory that lists 

equipment bearing the UL label. In the case of a directional 

sounder, the applicable test standard is UL 464, Audible 

Signal Appliances. Under this standard, a directional 

sounder is listed as a supplemental notification appliance.

What are the exits

where directional 

sounders can be used?

Often, the simplest way to identify the exits in a building 

is to look for the exit signs. With few exceptions, exit signs 

will be found at the termination of exit paths, such as exterior doors at ground level, doors into enclosed stairways, 

doors leading horizontally into an adjoining building or 

fire area, and doors leading to exterior stairways and fire 

escapes.

The exit as defined by NFPA 101 (2003 ed.), NFPA 5000 

(2003 ed.) and the 2003 ICC International Building Code 

is one specific travel element or section of the means of 

egress which is comprised of three distinct elements that 

are 1) the exit access, 2) the exit, and 3) the exit discharge.

The exit is the primary focus of a basic installation of 

directional sounders, and most often this will be at doors 

leading to the exterior, at doors into stairways, or at 

horizontal exit doors. Basic and enhanced installations are 

more fully described in the section of this guide entitled 

“Directional Sound Installations.” The three basic elements 

of the means of egress and the specific concepts of an exit 

passageway and a horizontal exit found in NFPA and ICC 

documents are described in the table on page 8.

Both code organizations use effectively the same concept 

in defining the exit. Figures 5 and 6 graphically illustrate 

the concepts of exit access, exit, and exit discharge.

The code definitions on page 8 provide the generic description of an exit, which in more specific terms, may be 

found as one of the following types of exits described and 

illustrated below.

• Doors leading directly to the outside at grade

• Doors leading into a protected passageway which leads 

to the outside at grade

Section 4

Locations for 

Directional Sounders

7
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

Enclosed

Exit Stair

Exit Access

Ends at Exit

Door

up

down

up

down

Enclosed

Exit Stair

X X

X

Exit Access Starts

At Any Point

X

X

X

Exit Access

Routes

Figure 5. Exit access starts from any normally occupied point on a floor and ends at the door 

leading into an exit.

Exterior Exit

Stairway

Exit

(From Grade Level)

Interior Exit

Stairway

Exit Discharge

Figure 6. Different types of exits illustrated.

• Interior stairs enclosed by fire rated construction, which 

includes

– Smokeproof towers

– Pressurized stairways

• Exterior stairs isolated from the building interior with fire 

rated or protective construction

• Passageways enclosed by fire rated construction (should 

not be confused with corridors)

• Horizontal exits

• Ramps enclosed by fire rated construction

• Escalators enclosed by fire rated construction

• Fire escapes

• Other special exits – Although the above listed items represent common types of exits found in buildings or structures, there are other types of open or unenclosed routes 

that may legally constitute an exit. These are sometimes 

the result of unique building conditions, a code equivalency or performance-based building design.

Figure 7 illustrates one of the most common arrangements 

of an exit, the fire resistive enclosed stair. Figures 8 and 9 

are enhanced versions of the same type of stair exit. Figure 

8 illustrates a smoke-proof tower arrangement that represents an enclosed stair preceded by an open-air balcony 

or vestibule. Similarly, Figure 9 shows an enclosed stair 

accessed via a vestibule that is mechanically ventilated. 

What are the areas of refuge or areas of rescue 

assistance where directional sounders can be used?

In 1990 the Federal Government passed the Americans with 

Disabilities Act which was the first large scale legislation 

to contain provisions for accessible means of egress for 

people with physical disabilities or mobility impairments, 

such as occupants using wheelchairs, walkers, crutches or 

canes. During the 1990s and up to the present time both 

the NFPA and ICC (and its predecessor organizations) have 

developed criteria for accessible means of egress consistent 

with the federal laws. In addition to federal law, both NFPA 

and ICC codes require that newly constructed buildings 

have accessible means of egress as defined by NFPA and 

ICC documents. An element of an accessible means of 

egress is often a specially provided space in the building 8

Basic Concepts – Means of Egress

NFPA Definitions ICC Definitions

Means of Egress – A continuous and unobstructed way of travel from any point in a 

building or structure to a public way consisting of three separate and distinct parts: 

(1) the exit access, (2) the exit, and (3) the exit discharge.

Means of Egress – A continuous and unobstructed path of vertical and horizontal 

travel from any occupied portion of a building or structure to a public way. A means 

of egress consists of three separate and distinct parts: the exit access, the exit and 

the exit discharge

Exit Access – That portion of a means of egress that leads to an exit. Exit Access – That portion of a means of egress that leads from any occupied portion 

of a building or structure to an exit.

Exit - That portion of a means of egress that is separated from all other spaces of a 

building or structure by construction or equipment as required to provide a protected 

way of travel to the exit discharge.

Exit - That portion of a means of egress that is separated from other interior spaces 

of a building or structure by fire-resistance-rated construction and opening protectives as required to provide a protected path of egress travel between the exit 

access and the exit discharge. Exits include exterior doors at ground level, exit 

enclosures, exit passageways, exterior exit stairs, and horizontal exits.

Exit Discharge – That portion of a means of egress between the termination of an exit 

and a public way.

Exit Discharge – That portion of a means of egress system between the termination 

of an exit and a public way

Exit Passageway - NFPA does not maintain a formal definition of exit passageway but 

does explain the concept in the Appendix of NFPA101 as follows: An exit passageway 

serves as a horizontal means of exit travel that is protected from fire in a manner 

similar to an enclosed stair.

Exit Passageway – An exit component that is separated from other interior spaces of 

a building or structure by fire-resistance-rated construction and opening protectives, 

and provides for a protected path of egress travel in a horizontal direction to the exit 

discharge or the public way.

Horizontal Exit - A way of passage from one building to an area of refuge in another 

building on approximately the same level, or a way of passage through or around a 

fire barrier to an area of refuge on approximately the same level in the same building 

that affords safety from fire and smoke originating from the area of incidence and 

areas communicating therewith.

Horizontal Exit - A path of egress travel from one building to an area in another building on approximately the same level, or path of egress travel through or around a wall 

or partition to an area on approximately the same level in the same building, which 

affords safety from fire and smoke originating from the area of incidence and areas 

communicating therewith.
S Y S T E M S E N S O R

up

down

Fire Door

Fire Rated Enclosed

Stairway

Figure 7. Fire-rated enclosed stair.

Fire Rating Based On

Number Of Stories

up

down

up

down

Fire Rated Exit Passageway

(Penetrations Restricted)

Corridor

Fire Rated Door

Figure 12. Floor exit arrangement showing a fire rated exit passageway leading to an 

enclosed exit stair. The doorway into the exit passageway constitutes the point 

of entry into the exit.

up

down Fire Door

Mechanical

Ventilation

Shaft

Fire Rated Enclosed

Stairway

Figure 9. Smokeproof tower, mechanically 

vented.

2 Hour Fire Barrier Doors are Automatic

or Self Closing Fire Doors

up

down

up

down

Enclosed Exit

Stair

Enclosed Exit

Stair

Figure 10. Building floor area served by enclosed exit stairs and horizontal exit fire barrier 

wall. Door openings through the 2-hour fire barrier qualify as exits.

9

8

7

6

5

4

3

2

1

6

5

4

3

2

1

Horizontal Exit from One

Building to Another Via Bridge

2 Hour Fire

Barrier Wall

Either or

Both Sides

Figure 11. Illustration of a horizontal exit using a bridge between two buildings.

9

Open to Outside updown

Fire Rated Enclosed

Stairway

Fire Door

Fire Door

Figure 8. Smokeproof tower.
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

called an area of refuge. In fully sprinklered buildings, any 

sprinklered story or floor of the building is effectively considered an area of refuge and; therefore, the areas of refuge

discussed herein are typically found in recently constructed 

(i.e. buildings built after 1990) non-sprinklered, multistory buildings. Buildings built prior to the passage of the 

Federal ADA laws typically are not required to have areas 

of refuge; however, state or local governments may have 

passed laws or ordinances that required areas of refuge in 

sprinklered and non-sprinklered buildings built before and 

after 1990.

Where areas of refuge have been designated, they typically 

will be a part of or immediately adjacent to a stairway 

that is part of the means of egress. As such, the directional sounder at the entrance to the stairway will serve to 

identify the location of the area of refuge – see Figure 13, 

below. A different situation exists when an elevator serving 

as an accessible means of egress has been provided, and 

includes the elevator lobby as an area of refuge as shown 

in Figure 14. Such means of egress elevators and associated 

refuge areas are now required by ICC in non-sprinklered 

buildings having more than four levels above or below 

the level of exit discharge (the ground floor, usually), and 

they are permitted by NFPA. In such cases, a directional 

sounder must differentiate between access to an area of 

refuge solely intended for those requiring assistance for 

exiting and access to an exit stairway.

An unusual condition that may be encountered is where an 

elevator is also part of the required means of egress. This 

may occur in a tower structure, such as an airport traffic 

control tower. In these cases, the access to the elevator is 

treated in the same manner as access to a stairway, and a 

directional sounder at the entrance to the elevator lobby or 

the elevator door, itself, may be appropriate. Using elevators as one of the recognized means of egress is likely to 

become more common in the future as codes are changed 

to reflect the reality of trying to evacuate tall buildings in 

an emergency.

What are other means of egress components 

where directional sounders can be used?

In addition to exterior doors, doors leading to stairs and 

ramps, and other common components of the exits previously identified, other types of exits and other components 

of the exit path may need directional sounders to assist in 

evacuation or relocation. In older buildings, fire escapes 

still are considered to be part of the required exit system, 

and they are likely to be identified by exit signs at the 

door or window leading to the fire escape, as well as in 

Basic Concepts – Area of Refuge

NFPA Definitions ICC Definitions

Accessible Means of Egress – A means of egress that 

provides an accessible route to an area of refuge, a 

horizontal exit, or a public way.

Accessible Means of Egress – A continuous and unobstructed way of egress travel 

from any point in a building or facility that 

provides an accessible route to an area of 

refuge, a horizontal exit, or a public way.

Area of Refuge – An area that is either (1) a story in a 

building where the building is protected throughout by 

an approved, supervised sprinkler system and has not 

less than two accessible rooms or spaces separated 

from each other by smoke resisting partitions; or (2) 

a space located in a path of travel leading to a public 

way that is protected from the effects of fire, either by 

means of separation from other spaces in the same 

building or by virtue of location, thereby permitting a 

delay in egress travel from any level.

Area of Refuge – An area where persons 

unable to use stairways can remain temporarily to await instructions or assistance 

during emergency evacuation.

up

down

30 × 48 Wheelchair Space Area of Refuge

Adjacent to Means of

Egress Stairway 48 Minimum

48 Minimum

up

down

Area of Refuge

In a Means of

Egress Stairway

48 Minimum

48 Minimum

Figure 13. Areas of refuge at stairways.

10

Accessible Elevator

X

up

down

Exit Access Starts

at Any Point

Protected

Area of Refuge

X

X

Accessible Exit

Access Routes

up

down

Figure 14. Area of refuge at elevator lobby, serving an accessible means of egress elevator.
S Y S T E M S E N S O R

the corridor access to the fire escape. At both locations, 

directional sounders will be useful in supplementing the 

visual signage.

Exit access includes the path of travel from any point in 

the building along aisles and corridors to an exit. A Type 2 

installation that provides sounders both at exits and in the 

exit access route is described in the section “Directional 

Sounder Installations,” following. Directional sounders 

in a Type 2 installation may be appropriate wherever 

supplemental signage is used to assist in identifying the 

exit access route. 

Most commonly, supplemental exit signage (typically, an 

exit sign with or without single or bi-directional arrows) 

is used at corridor intersections where the direction to the 

exit is not obvious and for long stretches of corridors or 

walkways where the exit sign at the exit is too far away to 

be readily seen. Not all of these sign locations are appropriate for a sounder — sound is omnidirectional and travels 

around corners. Each potential sounder location has to be 

analyzed individually. Sounders spaced too closely may 

cause confusion. See “Directional Sound Installations” for 

guidance.

Open stairways (i.e. stairways not within a fire-resistive 

enclosure) and walkways, under certain circumstances, 

may also be designated as a primary means of egress and 

are likely to be designated by exit signs. Directional sounders may be appropriate at these locations.

“Dead-ends” and common paths of travel are other components of the means of egress. The former (see definition, this page) can be a problem if a person becomes 

disoriented or fails to see an exit sign at the open end of a 

corridor that has only one way out. A directional sounder 

at the point where the “dead-end” corridor joins with paths 

to two (or more) exits will help to orient the occupant and 

lead the occupant away from a situation where the person 

can become trapped at the far, dead-end of the corridor.

Common paths of travel may include exit access travel in 

a dead-end corridor, but the most common situation is the 

travel from any point in a room to the room’s only door. 

Because two separate paths to an exit are not available 

within the room, that portion of the means of egress is a 

common path of travel. The codes limit the length of such 

common paths of travel, depending on the occupancy. In 

complicated situations, as for instance, when the space is 

broken up by filing cabinets, library shelving or other such 

obstructions, a directional sounder at the room’s exit door 

will better define the way out than an illuminated exit sign. 

Even though under such conditions an exit sign may be 

required only if the room is intended to be occupied by 

more than 50 persons, a sounder can be appropriate even 

for space intended for fewer than 50 persons, such as a 

library stack area.

Locations that may not be suitable for directional 

sounders

Under some circumstances, windows may be designated 

as an emergency means of escape. In schools and day 

care centers, they are designated as “windows for rescue,” 

intended to be used by firefighters to assist in evacuation, 

but not by the children on their own. In such locations, 

Other Means of Egress Features

NFPA Definitions ICC Definitions

Common Path of Travel – The length of travel 

measured in the same manner as travel distance 

but terminating at the point where two separate 

and distinct routes of travel become available. 

Separate paths that merge also are common paths 

of travel.

Common Path of Egress Travel – That portion of 

exit access which the occupants are required 

to traverse before two separate and distinct 

paths of egress travel to two exits are available. Paths that merge are common paths of 

travel.

Dead-End Corridor – (commentary) A condition 

where the corridor continues past an exit and creates a pocket into which an occupant might travel. 

Relatively short dead-ends are generally permitted.

Dead-End Corridor – not defined; assumed to 

be self-explanatory. A maximum dead-end corridor length of 20 feet is permitted.

Dead-End Corridor

updown

up

down

Enclosed Exit Stair

Figure 15. Dead-end corridor

Exit

Common Path of Travel

X

Dead-End

Exit

Figure 16. Common path of travel

11

sounders would serve no practical purpose. Windows 

designated for escape also may be encountered in apartments and private residences, where sounders would not 

be appropriate.

Sounders are not appropriate under other circumstances. 

A stairway may stop before it reaches a point where it discharges to a place of safety, instead discharging back into 

the building at a point that can be involved in fire or filled 
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

with smoke. Elsewhere in a building, an exit door or stairway may not be accessible because there is an intervening 

door that might be locked. An exterior door that appears 

to lead to a place of safety actually leads to an outdoor 

enclosed space from which there is no escape. The building codes do not allow such doors or stairs to be considered as exits, and typically, there would be no exit signage 

in connection therewith. But mislabeling can occur, and 

changes are made to buildings without a complete review 

of the means of egress. It is possible for an exit sign to be 

improperly placed at a door or stairway that does not lead 

to safety, and placing directional sounders at such locations must be avoided. (It should be noted that both NFPA 

and ICC documents permit ground-level discharge from a 

stair back into the building under prescribed conditions. In 

these cases the stair is consider a viable exit and should be 

marked accordingly as an exit) 

Portable ladders, rope fire escapes and similar escape 

devices, according to appendix material in the NFPA Life 

Safety Code, can be useful to facilitate escape from a burning building but may be unsuitable for use by aged or 

disabled people or by small children. Neither NFPA nor ICC 

recognizes these as legitimate exits, and directional sounders should not be used to identify their location.

For new buildings, particularly, both NFPA and ICC state 

that access to an exit shall not pass through a high-hazard 

occupancy, a kitchen, a storeroom or a closet. It is common, however, to find the second means of egress from 

a restaurant dining room to be through the kitchen, and 

there may be other circumstances where such “prohibited” 

means of egress are permitted. When such situations are 

encountered, the authority having jurisdiction should be 

contacted for the appropriateness of sounders at these 

apparent exit access paths.

12

General 

General guidance is provided in this section for directional sound installations 

for either new fire alarm systems or as enhancements to 

existing systems. Installation and maintenance instructions 

for the directional sounders provided by the manufacturer 

and NFPA 72 should be consulted for specific information 

related to mounting, device features, electrical wiring and 

appropriate settings.

Directional sound is a broadband, multi-frequency sound. 

A directional sounder should incorporate the capability 

to be set to multiple pulse patterns, each consisting of a 

period of directional sound interleaved with an optional 

voice message. The patterns are used to provide distinctive sound cues at an exit or along a route to the nearest 

exit and the voice messaging provides clear instructions to 

building occupants. 

The pulse patterns can be set to signify increasing proximity to an exit, the fastest pulse being used at the exit. Other 

audible information can supplement the pulsing broadband sound as guidance. For example, each pulse pattern 

is capable of being supplemented with other audible cues 

such as voice messaging instructing occupants that they 

are approaching a stairway going up or down, or that 

they have reached an exit. Another direction given is that 

occupants are approaching an area of refuge, which should 

be distinctly marked.

The application or installation of directional sounders in 

buildings or structures requires an understanding of basic 

egress concepts and features. Key concepts and features 

that are important considerations in developing and implementing an installation of directional sound devices have 

been reviewed and, again, are as follows:

• Exit access

• Exit

• Exit discharge

• Refuge area, area of refuge, or area of rescue assistance

• Horizontal exit

• Exit passageway

• Dead-end corridor

• Common path-of-travel

• A fire escape when recognized as an exit

The concepts used to position directional sounders differ 

from the concepts applied to standard notification appliances (See System Sensor “Audible/Visible Appliance 

Guide”). Generally, fire notification appliances in buildings, such as bells, horns and speakers, require placement 

at numerous locations in order to achieve the sound levels 

that can be heard and understood by occupants throughout 

all building areas. NFPA 72 would consider this a “public 

mode” application.

A symbol different from the traditional fire alarm devices 

should be used for directional sounders on installation 

floor plans. The following symbol is used in this guide and 

is suggested for general usage: 

Figure 17. Directional sounder icon

Type 1 (Basic) Installation

A Type 1 installation calls for directional sound devices 

at the location of code-required exits and areas of refuge. 

The intent is to place a directional sound device in close 

proximity to the door of each exit or area of refuge as an 

audible cue for locating it in an emergency. 

Examples of Type 1 installations are shown in Figures 18 

through 20.

In a Type 1 installation of directional sounders, the concern 

is not for establishing an audible signal in all occupied 

building spaces. Rather, the focus is to provide sound cues 

to assist occupants in more easily locating the point of 

entry to an exit or area of refuge during an evacuation and 

under possibly smoky conditions. The key considerations 

for establishing a Type 1 installation are as follows:

• Using the guidance in the section “Locations for 

Directional Sounders,” identify the doors leading to 

exits and areas of refuge. Also, identify areas where 

directional sounders should not be used.

• Determine the position of directional sounders based 

on the recommended installation zones for doors, using 

the guidance in the following section “Positioning 

Directional Sounders on Wall and Ceiling Surfaces.”

Section 5

Directional Sound 

Installations
S Y S T E M S E N S O R

• Determine the ambient sound levels for the location of 

each exit or area of refuge door. Specify the power setting that will result in a minimum 15 dBA sound level 

above ambient sound levels at ten feet from the device. 

Power settings resulting in a sound level in excess of 

15 dBA above ambient are acceptable where greater 

sound level penetration is desired.

• Directional sounders located at exit doors are set to the 

fastest pulse pattern and may the incorporate the voice 

message “Exit Here.”

• Directional sounders located at stairwells are set to the 

fastest pulse pattern and may incorporate the voice 

messages “Stairs Up” or “Stairs Down”, depending on 

the orientation to ground level.

• Directional sounders located at doors leading to exit 

stairs that also have an area of refuge at or adjoining 

the landing are set to a fast pulse pattern, followed by 

the distinctive “area of refuge” supplemental indicator.

Enclosed

Exit Stair

Enclosed

Exit Stair

up

down

downup

Area of

Refuge

Area of

Refuge

Sounder Set to ‘Fast’ Pulse Plus

Refuge Tone to Mark Entrance

to Exit Stair and Adjoining Area

of Refuge

Sounder Set to 

Fast’ Pulse to

Mark Exit Stair

Sounder Set to ‘Slow’ Pulse

Plus Refuge Tone to Mark Area

of Refuge That is Not an Exit

KEY

Exit Sign Shaded Quadrant

Represents Visible Face

Exit Sign With Designation

of Directional Arrow

Directional Sounder

Full Height Walls

Partial Height Dividers

Figure 18. Directional sounders at exit stairways and areas of refuge in a Type 1 installation.

up

up

down

down

Common Path of Travel

Dead-End Dead-End

In open-plan floors, Type 2

sounders should not be used for

other than dead-ends or common

path of travel conditions.

Multiple sounders in the common

egress route of an open floor

plan would result in conflicting

directional sound cues. Type 1

sounders may need to have the

power setting increased for

better penetration into the open

floor space.

KEY

Exit Sign Shaded Quadrant

Represents Visible Face

Exit Sign With Designation

of Directional Arrow

Directional Sounder

Full Height Walls

Partial Height Dividers

Figure 19. Directional sounders in an open-plan building.

13
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

• In some cases, it may be beneficial to use additional 

directional sounders prior to the location of the exit 

where intervening doors occur along the egress path, 

such as cross corridor doors which are self-closing 

or automatic closing. When such intervening doors 

significantly reduce the penetration of the directional 

sounder mounted at the exit along the egress pathway 

an additional sounder installed at the intervening doors 

will provide a sound cue for occupants seeking the exit 

located beyond the intervening doors (see Figure 20). 

• A building’s emergency planning documents, including occupant training procedures, should be revised 

to reflect the meanings of the “slow” and “fast” pulse 

directional sounds and the supplemental signals.

Type 2 (Enhanced) Installation

A Type 2 installation is an enhanced Type 1 installation. In 

addition to the sounders needed for a Type 1 installation, 

it provides devices that give audible directional cues at 

key points along the means of egress, thereby guiding the 

person towards the exit or area of refuge. Locations to be 

considered for supplemental directional sounders in a Type 

2 installation include the following:

• door from a room/area having a common path-oftravel,

• the outlet end of a dead-corridor,

• at points of multiple route choice where a directional 

sound device is located leading in the direction of the 

nearest exit, 

• at points along a route where the sounder at the exit 

is not audible. In this case a directional sounder is 

installed to act as a locator of the egress route to the 

exit.

Care must be taken in a Type 2 installation to guide the 

person in just one direction, generally the direction that 

leads to the closest exit. Situations that can lead a person 

into a circular route or into a dead-end must be avoided. 

A Type 2 installation requires additional analysis effort 

and design specification to properly implement directional 

sounders. The key considerations for establishing a Type 2 

installation are as follows: 

• Include all directional sounders necessary for a Type 1 

installation.

• Use additional directional sounders where they will 

enhance the ability of occupants to locate exits and the 

direction thereto. When locating a directional sounder 

at a point where the egress path turns or changes 

direction, preferably locate the sounder past the turn 

but no further than approximately 2 feet past the turn. 

It is also acceptable to locate the sounder just before 

the turn. See Figure 21 for the recommended zone for 

locating sounders at turns in the egress route such as 

a corridor.

• In some cases, it may be beneficial to use additional 

directional sounders where intervening doors are 

located along an egress path such as cross corridor 

doors which are self-closing or automatic closing. 

When such intervening doors significantly reduce the 

penetration of directional sound along the egress pathway an additional sounder installed at the intervening 

doors will provide a sound cue for occupants following 

the egress route that continues beyond the intervening 

doors. (See Figure 22.)

14

Fire Rating Based on

Number of Stories

up

down

up

down

Corridor

Set Directional

Sounder to ‘Fast’

Pulse Pattern

Intervening Door

Additional sounder set to ‘Fast’ pulse to increase the directional sound penetration

into the corridor once the intervening door closes. The sounder should be located

on the corridor side of the door. Once the evacuees pass through the door they will

begin to hear the sounder at the stairwell and proceed towards the actual exit.

Figure 20. Floor exit arrangement showing a corridor leading to an enclosed exit stair. Example indicating when directional sounders should be placed at an intervening door.

2 FT.

Direction of Travel to

the Nearest Exit

Center Line of Corridor

Preferred

Installation

Zone

Acceptable

Installation Zone

Direction of Travel to

the Nearest Exit

Figure 21. Preferred and acceptable zones for location of directional 

sounders at a turn in the exit access route.
S Y S T E M S E N S O R

15

Enclosed Exit Stair

up

down

‘Fast’ Pulse

‘Medium 1’ Pulse

‘Medium 2’ Pulse

‘Slow’ Pulse

KEY

Directional Sounder

Full Height Walls

Partial Height Dividers

Figure 23. Level 2 sounders in a long corridor, with slow to fast pulse patterns along the exit access route towards the exit.

Enclosed Exit Stair

up

down

 ‘Fast’ Pulse

Location B

‘Medium 1’ Pulse

Location A

‘Medium 2’ Pulse

 ‘Slow’ Pulse

For an intervening door close to a sounder, an

additional sounder before the door may not be

necessary. An appropriate alternative would be

relocating the sounder from location B ahead

of the door.

The intervening doors, when closed, are likely to reduce the sound

penetration of the sounder at location A. Therefore, an additional

sounder would be appropriate before the intervening doors. In

this case the sounder mounted before the doors would be set to a

‘Medium 2’ pulse the same as the sounder at location A.

Relocation

Alternative

KEY

Directional Sounder

Full Height Walls

Figure 22. Building floor area served by enclosed exit stairs with intervening doors along egress route. Example indicating when additional 

directional sounders may be necessary at intervening doors.

• Use increasing speed in pulse patterns in moving from 

sounder locations most distant from the exit (slower 

pulse) to sounders nearer the exit (faster pulse). (See 

Figure 23.)
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

Enclosed Exit Stair

up

down

‘Fast’ Pulse

‘Medium 1’ Pulse

‘Medium 2’ Pulse

‘Slow’ Pulse

‘Medium 2’ Pulse

Same Pulse OK If Not

Same Route to Exit

Not More Than Four

Sounders Along Same

Route to Exit

KEY

Directional Sounder

Full Height Walls

Figure 24. Sounders in a Type 2 installation in a long, complex exit access route.

Key Decision

Point

Key Decision

Point

Route A

Exit Exit

Exit

Considerations for Occupant Load Balance:

Although Route A is the shortest travel

distance to an exit, Type 2 sounders are not

recommended to be located along Route A

due to the limited exit capacity. Where

occupant balance issues may be present, it

is recommended that directional sounders

be limited to a Type 1 installation (exits only).

Auditorium

(400 Occupants)

KEY

Exit Sign Shaded Quadrant

Represents Visible Face

Exit Sign With Designation

of Directional Arrow

Directional Sounder

Full Height Walls

Figure 25. A Type 2 installation should not be used where supplemental sounders may not lead to the 

most appropriate exit.

• Do not use more than 

four sounders in the route 

towards an exit. Only four 

pulse patterns are available 

(including that of the Type 

1 sounder at the exit), and 

using two sounders with 

the same pulse patterns 

along the same route may 

cause confusion on the 

direction to the nearest 

exit. (See Figure 24.)

• Use a maximum separation 

of 50 to 80 feet between 

sounders along the egress 

path. In general, directional sound pressure will 

reduce by 6dB for every 

doubling of distance. In 

high sound absorbing 

locations the maximum 

separation between directional sounders may need 

to be reduced. As indi16

cated in Figure 28, sound pressure levels will drop 

to an ambient level at a distance of approximately 56 

to 100 feet for sounders set to a sound pressure level 

of 15 to 21 dB above ambient (measured at 10 feet 

from device), respectively. As a general rule spacing 

sounders in the range of 50–80 feet apart will provide 

readily identifiable sound cues as occupants move 

through exit routes. Such spacing will result in occupants approaching the audible zone of the directional 

sounder within several steps after passing a previous 

sounder location. 

• Use Type 2 sounders in rooms or spaces having an 

open floor plan with a single means of egress that 

constitutes a common path of travel.

• A building’s emergency planning documents, including occupant training procedures, should be revised 

to reflect the meanings of the “slow” and “fast” pulse 

directional sounds and the supplemental signals.

A Type 2 installation is not always appropriate: 

• Do not use a Type 2 installation for open floor plans 

with multiple exits, where sounders will tend to conflict with each other.

• Do not use a Type 2 installation where occupant loads 

and exit capacities are not reasonably balanced with 

travel distances to routes. (See Figure 25.)

Additional illustrations of Type 2 installations can be found 

in Figures 26 and 27.
S Y S T E M S E N S O R

17

Enclosed

Exit Stair

down

up

Enclosed

Exit Stair

up

down

Sounder Set to

‘Fast’ Pulse to

Mark Exit Stair

Sounder Set to Fast

Pulse to Mark Exit Stair

Corridor A

Corridor C

Corridor B

No directional sounder is needed

in corridor with alternative

directions of movement

Directional sounder is located in Corridor C in

proximity of exit sign; intent is to provide sound

cue outside Corridor B leading to direction of

exit stair. Sounder set to ‘Medium 1’ pulse.

Directional sounder is located in Corridor A in

proximity of exit sign; intent is to provide sound

cue outside Corridor B leading to direction of

exit stair. Sounder set to ‘Medium 1’ pulse.

Suite with Common

Path of Travel

Directional sounder is located to

Provide sound cue of location of

Suite egress door. Sounder set to

‘Medium 2’ pulse (optional if corridor

Sounders are not audible).

KEY

Exit Sign Shaded Quadrant

Represents Visible Face

Exit Sign With Designation

of Directional Arrow

Directional Sounder

Full Height Walls

Partial Height Dividers

Figure 26. Example of a Type 2 installation. 

Key decision points should be

identified as locations for

directional sounders. The

sounders are located on the

side of the exit signs that is

nearest an exit.

up

down

up

down

Key egress decision point. For Type 2 installation locate

directional sounder in direction of nearest exit.

Decision point with 4 egress

rouite choices. Directional

sounder is not recommended

in these nearby corridor

areas to avoid conflicting

sound cues.

Key Decision Point

Key Decision Point

Key Decision Point

A

C

B Sounder placed at this

location so that building

occupants originating

from points A, B, or C will

follow the

shortest

path to

an exit.

KEY

Exit Sign Shaded Quadrant

Represents Visible Face

Exit Sign With Designation

of Directional Arrow

Directional Sounder

Full Height Walls

Figure 27. A Type 2 installation with multiple egress route decision points.

Directional sounders are 

at exit stairways and at 

key egress route changes. 

Sounders in the corridor 

along the exit access route 

are needed if the directional 

sounders at the stairways 

are not audible.
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

Special Considerations for Dead-Ends

Figures 29 and 30 illustrate common types of dead-end corridor conditions. In each case, when a directional sounder 

is used in a Type 2 installation, it should be located fully 

outside the dead-end corridor, such that a person will be 

directed out of the dead-end and towards the nearest exit. 

No sounder should be placed within the dead-end portion 

of the corridor as it may draw persons outside the deadend into the dead-end condition.

The shaded portions on the diagrams (Figures 29 and 30) 

give the preferred location of Type 2 sounders in each 

instance. To guide the occupants in the proper direction, 

the sounder should be placed into the access route to the 

nearest exit, past the dead-ends by not more than two feet. 

It can be either wall or ceiling-mounted. Once past this 

sounder, they should hear a more rapidly pulsed sounder 

in the direction of the exit. 

The Type 2 sounder at the end of a dead-end corridor 

may be unnecessary if either the Type 1 sounder at the 

nearest exit or another Type 2 sounder in the exit access 

route is close by and readily audible at the far end of the 

dead-end.

up

down

Dead-End

2’

Exit Stair

Path to

Alternate Exit

Path to

Nearest Exit

* Not needed if sounder at stairway

is audible at far end of dead-end.

Locate Type 2

Directional

Sounder Here*

KEY

Directional Sounder

Full Height Walls

Figure 29. Directional sounder at single dead-end corridor.

Dead-End

Corridors

No Sounder

No Sounder No Sounder

Path to Exit

2’

Type 2 Directional

Sounder Location

KEY

Directional Sounder

Full Height Walls

Figure 30. Directional sounder at multiple dead-end corridors.

Sound Pressure vs. Distance from Directional Sounder 

–5

0

5

10

15

20

25

10 20 30 40 50 60 70 80 90 100

Distance from Sounder (Feet)

Sound Pressure above 

ambient (dB)

Figure 28. Sound pressure of directional sound compared to ambient as a function of distance from the 

directional sounder.

Note: Initial sound pressure of directional sound set at 15dB, 18dB and 21dB greater than ambient at 10 feet.

18
S Y S T E M S E N S O R

A directional sounder 

should be installed in close 

proximity to the location 

of a door or multiple doors 

that provide the initial entry 

point into or through the exit or area of refuge. In the case 

of smoke-proof towers or exit passageways that lead to 

an enclosed stair, the initial entry point is the first door 

encountered in the path into the smoke-proof tower or 

into the exit passageway. The following figures illustrate 

recommended zones for locating directional sounders on 

the wall or on a ceiling in cases where sufficient wall space 

for mounting a device is not available.

In the case of open floor plans, partial-height partitions can 

pose a sound absorbing obstruction to a directional sound 

device. The directional sounder shall be placed above the 

level of room dividers, preferably one to two feet higher. 

Figure 36 illustrates the desirable distance that a directional sounder should be installed above the highest partition, 

or divider, in the space.

Additional sounders may be needed at multiple arrays of 

multiple doors, based on sound pressure.

Floor

Door Handle

Height

Ceiling

Center Line of

Door

EXIT

12 in.

24 in.

Hatch Area is

Preferred

Zone for

Location of

Directional

Sounders

Hatch Area is

Acceptable

Zone for

Location of

Directional

Sounders

Example

Locations for

Directional

Sounders

Example

Locations for

Directional

Sounders

Single Door

Figure 31. Sounder locations adjoining a single door.

Floor

Ceiling

Center Line of

Door

EXIT

12 in.

24 in.

Hatch Area is

Recommended

Zone for

Location of

Directional

Sounders

Example

Locations for

Directional

Sounders

Double Door

Figure 32. Sounder locations adjoining a double door.

Floor

Ceiling

Center Line

of Device

2 ft.

Where limited

wall surfaces

are available, a

ceiling mount

installation

with directional

sounder no more

than 2 feet distance

off face of door.

Example

Locations

for

Directional

Sounders

Side View

Floor

Ceiling

Front View

Figure 33. Ceiling-mounted sounders.

19

Section 6

Positioning Directional 

Sounders on Wall and 

Ceiling Surfaces
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

Where Directional Sounders Are Oriented

toward a space with partial height dividers

it is recommended that the directional

sounder be above the top of tallest divider

or partition.

24 in.

Directional Sounder

Side View

Floor

Ceiling

Enclosed

Exit Stair

60 in.

Desirable

Figure 36. Sounder location above level of room dividers.

Floor

Center Line of

Door Array

EXIT

36 in.

24 In.

Hatch Area Is Recommended

Zone for Location of

Directional Sounders

Example Locations for

Directional Sounders

Door Array – Recommended Location

for Multiple Door Installation

EXIT

36 in.

Figure 34. Sounder locations at multiple doors.

Wide Corridor

Center Line of Door

Array

36 in.

24 in.

Hatch Area is Recommended

Zone for Location of

Directional Sounders

Example Locations

for Directional

Sounders

Where egress approach is from one direction, the directional sounder

should be located over both sets of doors encountered.

36 in.

EXIT

Example Separation of 6 ft.

Separation May Be Larger

Wall Ends Direction Of

Egress Approach

Center Line of Door

Array

36 in.

24 in.

Hatch Area is Recommended

Zone for Location of

Directional Sounders

Example Locations

for Directional

Sounders 36 in.

EXIT

Figure 35. Sounder location at single-directional approach to multiple doors.

20
S Y S T E M S E N S O R

1. What is a directional 

sounder and how does it 

work?

A directional sounder is a 

type of electronic signaling device that is installed as 

part of a building fire alarm system. When activated, it 

produces short bursts of broadband sound in a frequency 

range that is distinctive from the audible sounds of bells, 

horns, or voice speakers. The broadband sound pulses of 

directional sounders make use of our natural ability to 

localize the sound sources.

2. What does the term “Directional” refer to?

The term “directional” refers to the unique characteristics 

of the sound that allow listeners to identify exactly where 

the sound is coming from. It does not in any way refer to 

the orientation or direction that the sound emanates from 

the sounder.

3. What is the advantage of adding directional sounders to a building’s emergency egress facilities?

Directional sound technology offers a solution to improve 

the exit or escape situation for building occupants. To 

help occupants in finding their way to an exit, refuge area 

or other means of egress, directional sounders integrated 

with the fire alarm system provide additional auditory 

information that can assist or aid occupants in locating 

escape routes without conflicting with the traditional fire 

alarm system notification appliances such as bells, horns, 

or voice speakers. Directional sounders effectively serve 

as “audible exit signs.” They are installed at exits and at 

points in between as an additional cue for persons needing 

to find exits and areas of refuge in an emergency. Because 

sound travels around corners, directional sounders are not 

line-of-sight dependent, and their unique audibility is an 

assist for persons with visual impairments.

4. What activates and powers the directional sounders?

Directional sounders are wired into and powered by the 

alarm notification circuits of the building’s fire alarm systems. Directional sounders are intended to operate simultaneously with the traditional fire alarm notification devices 

and to be wired as part of the fire alarm system notification 

circuits. There is no need to have a separate control panel 

for directional sounders.

5. Can directional sounders be installed as part of any 

fire alarm system?

Directional sounders should be compatible with the manufacturer’s recommended power supplies for the fire alarm 

system in which the sounders are used. Additional power 

supplies may be needed to handle the added current draw 

of the directional sounders.

6. What is a Type 1 (basic) directional sounder installation?

A Type 1 (basic) directional sounder installation is focused 

on providing directional sounders only at “exits” and 

“areas of refuge” as defined by building and fire codes. 

Such an installation typically includes a sounder at exterior exit doors, at doors leading into enclosed stairways or 

ramps, at the entrance to areas of refuge, at horizontal exit 

doors, and at other points defined as an “exit” or “area of 

Refuge” by applicable codes or standards.

7. What is a Type 2 (enhanced) directional sounder 

installation?

A Type 2 installation is an enhanced Type 1 installation. In 

addition to the sounders needed for a Type 1 installation, 

it provides devices that give audible directional cues at 

key points along the means of egress, thereby guiding the 

person to a nearby exit or area of refuge. In a Type 2 installation additional directional sounders can be used to mark 

the direction away from a dead-end corridor situation or 

identify the single means of egress from a room or space.

8. Are all installations either Type 1 or Type 2?

Type 1 installation refers to an installation that locates 

directional sounders only at the exits. Type 2 installation 

refers to an installation that includes additional sounders 

throughout the egress pathways. There may be situations 

where a Type 1 installation is desired, however due to special situations, some additional sounders may be required. 

An example of a special situation might include the case 

where locating sounders only at the exit may not provide 

adequate sound penetration to reach the majority of the 

occupants. These installations may not be considered 

Type 2 installations since the objective isn’t to identify the 

entire egress pathway even though additional sounders 

are used.

9. How many directional sounders are needed in a 

building?

Just as the numbers of traditional fire alarm signals are 

dictated by the size, configuration, noise levels and sound 

attenuation characteristics of a building, so are the numbers of directional sounders dependent on the characteristics of the building. It has to be taken into consideration 

whether a Type 1 or a Type 2 installation is being provided. 

Other considerations are the number of ground floor exits, 

the number of exit stairways and ramps, the complexity 

of exit access routes, the sound attenuation characteristics 

in the vicinity of sounder locations, ambient sound levels, 

and other parameters specific to each building. As a general guide, directional sounders are sufficiently audible at 

distances of 50 to 100 feet.

10. Are directional sounders UL listed?

In the case of a directional sounder the applicable test 

standard is UL 464, Audible Signal Appliances. Per this 

standard the System Sensor directional sounder device is 

listed as a “supplemental notification appliance.”

11. Are there some locations that are not suitable for 

directional sounders?

Directional sounders should not be placed at means of 

escape that are not recognized as “exits” by codes and 

standards, such as emergency rescue windows. Also, 

directional sounders should be avoided if they might create 

confusion on the nearest or best exit to use. In large, open 

areas, there may be multiple exits, but multiple directional 

sounders can cause interference with each other.

21

Section 7

Frequently Asked 

Questions
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

ADA The American With 

Disabilities Act. An act of 

Congress signed into law 

in 1990 intended to ensure civil rights for people with 

disabilities.

ADAAG The Americans With Disabilities Act Accessibility 

Guidelines. Developed as “rules” for accessible design. 

ADAAG includes both scoping and technical requirements 

for building design and construction.

Area of refuge A space within a building, separated from 

the remainder of the building by fire-resistive construction, 

that serves as a relatively safe staging area for people who 

cannot easily use stairways while awaiting assistance for 

evacuation. Also known as “area of rescue assistance.”

Average ambient sound The average sound level measured in a given area over the period of occupancy.

Bandwidth The frequency range of an audible appliance, 

measured in cycles per second, or Hertz (Hz). Audible fire 

alarm appliances typically are in the 3000 Hz range, while 

directional sounders cover most of the spectrum capable 

of being heard by the human ear (approximately from 20 

to 20,000 Hz).

Corridor dead-end That portion of a corridor that has 

only a single direction of travel towards an exit.

Exit That portion of a means of egress that is separated 

from the building to afford a protected path of travel to 

the exterior. Typically, the exit starts at an exterior door, 

a door into an enclosed stairway, or at doors of an horizontal exit.

Exit access That portion of a means from egress leading 

from any occupied portion of a building to an exit.

FHA The Fair Housing Amendment Act is federal legislation promulgated by the United States Department of 

Housing and Urban Development. The FHA provides for 

fair housing protection against discrimination on the basis 

of family status or persons with disabilities.

FHAG The Fair Housing Accessibility Guidelines. The 

FHAG includes both scoping and technical requirements 

for a broad category of residential construction.

ICC International Code Council, Inc. Publishers of the 

International Building Code, International Fire Code and 

other, related documents.

NFPA National Fire Protection Association. Publishers of 

fire safety codes and standards, like the Life Safety Code 

and National Fire Alarm Code, and NFPA 5000, a model 

building code.

Traditional fire alarm signal Audible and visual fire and 

evacuation notification appliances of a fire alarm system, 

such as horns, bells, speakers, and strobes.

22

Section 8

Glossary
S Y S T E M S E N S O R

5. Blauert, J. (1997) Spatial Hearing, Cambridge, MA: MIT Press.

6. Withington, D. J., Localisable Alarms, extract from N.A. Stanton 

and J. Edworthy (eds), Human Factors in Auditory Warnings, 

Ashgate Publishing Ltd. (1999).

7. Withington, D. J. 2002b, Life Saving Applications of Directional 

Sound, in M. Schreckenberg and S. D. Sharma (eds), Pedestrian and 

Evacuation Dynamics (Berlin/New York: Springer).

8. National Fire Protection Association, National Fire Alarm Code, 

Quincy, MA: 2002, 137.

9. National Fire Protection Association, op. cit., 138.

1. Sime, Jonathan, “Movement Toward the Familiar Person and 

Place Affiliation in a Fire Entrapment Setting, “ Environment and 

Behaviour 17:6 (1985) 697-724.

2. McClintock, T., et al, “A Behavioral Solution to the Learned 

Irrelevance of Emergency Exit Signage,” 2d International Symposium 

on Human Behavior in Fire, March 26-28, 2001, Boston, MIT 

InterScience Communications, 23-33.

3. SFPE Engineering Guide, Human Behavior in Fire, Society of Fire 

Protection Engineers, Bethesda, Maryland, 2003.

4. F.L. Wightman and D.J. Kistler, Sound Localization, in W.A. Yost, 

A. N. Popper and R.R. Fay (eds), Human Psychophysics, New York: 

Springer-Verlag (1993).

References

23
E X I T P O I N T TM D I R E C T I O N A L S O U N D E R

24

List of Illustrations

Figure 1. Interaural time and intensity differences of sound.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 2. Examples of frequency dependent attenuation for sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. Typical ambient sound levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 4. Frequency response of traditional fire alarm signals versus directional sounder. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Figure 5. Exit access starts from any normally occupied point on a floor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 6. Different types of exits illustrated.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 7. Fire-rated enclosed stair.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 8. Smokeproof tower.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 9. Smokeproof tower, mechanically vented.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 10. Building floor area served by enclosed exit stairs and horizontal exit fire barrier wall.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 11. Illustration of a horizontal exit using a bridge between two buildings.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 12. Floor exit arrangement showing a fire rated exit passageway.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Figure 13. Areas of refuge at stairways.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 14. Area of refuge at elevator lobby, serving an accessible means of egress elevator.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Figure 15. Dead-end corridor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 16. Common path of travel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Figure 17. Directional sounder icon. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 18. Directional sounders at exit stairways and areas of refuge in a Type 1 installation.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 19. Directional sounders in an open-plan building.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 20. Floor exit arrangement showing a corridor and intervening door scenario.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 21. Preferred and acceptable zones for location of directional sounders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Figure 22. Building floor area served by enclosed exit stairs and horizontal exit fire barrier wall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 23. Level 2 sounders in a long corridor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 24. Sounders in a Type 2 installation in a long, complex exit access route. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 25. A Type 2 installation should not be used where supplemental sounders may not lead to the most appropriate exit. . . . . . . 16

Figure 26. Example of a Type 2 installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 27. A Type 2 installation with multiple egress route decision points.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 28. Sound pressure of directional sound compared to ambient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 29. Directional sounder at single dead-end corridor.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 30. Directional sounder at multiple dead-end corridors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 31. Sounder locations adjoining a single door. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 32. Sounder locations adjoining a double door. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 33. Ceiling-mounted sounders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 34. Sounder locations at multiple doors.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 35. Sounder location at single-directional approach to multiple doors.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Figure 36. Sounder location above level of room dividers.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
©2007 System Sensor. The company reserves the right to change specifications at any time. A05-1048-001 • 3/07 • #1786