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Communication Systems for

Disabled Users of Buildings

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Washington, DC 20234

December 1 981

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Sponsored by

Architectural and Transportation Barriers Compliance Board

MATIONAL VtnUEAU OF BTAMDABOa

I.1BBABT NBSIR 81-2428

COMMUNICATION SYSTEMS FOR

DISABLED USERS OF BUILDINGS

Belinda L. Collins

William F. Danner

Robert L. Tibbott

FEB 3 1982

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U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Physics Division

Washington, DC 20234

December 1 981

Sponsored by

Architectural and Transportation Barriers Compliance Board

U.S. DEPARTMENT OF COMMERCE. Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director
^4'.T
ABSTRACT

Communication systems in buildings are designed to provide both emergency and

directional information to all building users. Yet such systems, which are typically comprised of visual signs and audible alarms, may fail to reach some

of the estimated twenty-seven million hearing or vision Impaired people in the

United States. As a result, a number of alternative communication systems have

been proposed for inclusion in accessibility guidelines. In the following

pages the research base underlying communication provisions for each of three

sensory modalities, vision, hearing and touch, are reviewed. In addition,

various proposed code recommendations are presented and discussed. The adequacy

of the research base for each provision is discussed along with the need for

various code provisions. It is noted that code provisions for tactile warnings

and exit markings are particularly Inadequate. Recommendations for further

research into tactile warnings, tactile signage, and visual alarms are suggested.

Key Words; accessibility; alarms; blind; communication; code requirements;

deaf; directional indicators; handicapped users; tactile warnings.
TABLE OF CONTENTS

Page

1 . GENERAL INTRODUCTION 1

2. INTRODUCTION TO VISUAL COMMUNICATION REQUIREMENTS 2

2.1 VISUAL IMPAIRMENT 2 2.1.1 Definitions and Extent of Visual Impairment 2 2.1.2 Types of Visual Impairment 3

2.2 OTHER IMPAIRMENTS 4

2.3 EVALUATION OF PROVISIONS FOR VISUAL COMMUNICATION SYSTEMS 4

2.3.1 Visual Alarms 4

2.3.2 Flash Frequency 5

2.3.3 Character Dimensions 7 2.3.4 Character Contrast 8

2.3.5 Character Size 9

2.3.6 Sign Location 10

2.4 CONCLUSIONS AND SUGGESTIONS FOR FURTHER RESEARCH 10

3. INTRODUCTION TO AUDITORY COMMUNICATION REQUIREMENTS 12

3.1 HEARING IMPAIRMENT 12

3.1.1 Definitions and Extent of Hearing Impairment 12

3.1.2 Types of Hearing Impairment 13

3.1.3 Other Impairments 14

3.2 EVALUATION OF PROVISIONS FOR AUDITORY COMMUNICATION SYSTEMS .. 14

3.2.1 Audible Warning Systems 14

3. 2. 1.1 Audible Alarms 14

3. 2. 1.2 Appendix to Audible Alarms 17

3.2.2 Speech Communication Systems 19

3. 2. 2.1 Placement of Listening Systems 19

3. 2. 2.Types of Listening Systems 20

3. 2. 2.

Telephones 20

3. 2. 2.Appendix to Placement of Listening Systems ... 20

3. 2. 2.

Appendix to Types of Listening Systems ....... 21

3. 2. 2.

Appendix to Telephones 21

3.2.3 Sound Reinforcement Systems 22

3.3 SUMMARY/CONCLUSIONS 22

3.3.1 Overview 22

3.3.2 Audio Alerting Systems 22

3.3.3 Speech Communication Systems 23

3. 3. 3.1 Statement of the Problem 23

3. 3. 3.

Approach to Speech Communication Systems 24

3. 3. 3.

Economic Considerations 26

iv
TABLE OF CONTENTS (cont.)

Page

3.4

FURTHER RESEARCH 26

4. INTRODUCTION TO TACTILE COMMUNICATION REQUIREMENTS 28

4.1 CODE REQUIREMENTS 28

4.2 TACTILE WARNINGS ON HORIZONTAL SURFACES 33

4.3 DIRECTIONAL AND INFORMATIONAL CUES 37

4.3.1 Skin Sensitivity 41

4.3.2 Visual Impairments and Tactile Sensitivity 42

4.3.3 Braille Sensitivity 43

4.3.4 Shape Senslvlty 44

4.3.5 Tactile Door Markings 48

4.4 CONCLUSIONS 52

4.5 TACTILE RESEARCH NEEDS 53

5. CONCLUSIONS 54

6. REFERENCES 56

V
LIST OF TABLES AND FIGURES

Page

Table 1. Estimates of the Population Distribution Average Hearing

Loss (AHL) at 500, 1000, and 2000 Hz in the Better Ear,

for Four Stages of Hearing Disability Classified by Degree

of Auditory Handicap 13

Table 2. ATBCB Part 1190 - Minimum Guidelines and Requirements for

Accessible Design 15

Table 3. Code Requirements for Tactile Warnings 29-30

Table 4. Tactile Warnings for Horizontal Surfaces from Other Codes ... 32

Table 5. Code Requirements of Tactile Communication 38

Table 6. Tactile Communication Requirements from Other Codes 39

Table 7. Code Requirements for Tactile Warnings on Doors and Vertical

Surfaces 49-51

Table 8. Recommended High Priority Areas for Research on Building

Communication Systems for Disabled Users 55

Figure 1. ANSI A117.1 (1980) Diagram of Tactile Warning at Hazardous

Vehicular Areas 31
SI CONVERSION UNITS

The units and conversion factors given in this table are in agreement with the

International System of Units or SI system (Systeme International d 'Unites).

Because the United States is a signatory to the 11th General Conference on Weights and Measures which defined and gave official status to the SI system,

the following conversion factors are given.

Length

1 in = 0.0254* meter

1 ft = 0.3048* meter

Area

1 in^ = 6.4516* x 10“^ meter^

Illumination

1 ft candle = 10.76 lux

* Exactly

vii
FOREWORD

The Architectural and Transportation Barriers Compliance Board (ATBCB) was created by PL 91-205, Amendments to the Architectural Barriers Act (1970).

This Board is composed of the heads of, or representatives from, the following

federal agencies: Departments of Health and Human Services; Education; Defense;

Justice; Transportation; Housing and Urban Development; Labor; Interior;

General Services Administration; United States Postal Service; and the Veteran's

Administration. In addition, 11 public members, of which at least five must be

handicapped individuals are appointed by the President. The Board's purpose

is to ensure compliance with the Architectural Barriers Act, to conduct research

related to architectural barriers, and to bring civil action in Federal court

to enforce provisions of the act in any non-complying Federal department or agency. The Board is also empowered to develop minimum guidelines for accessibility. These proposed guidelines are referred to as the ATBCB rule (1981) in

the following pages; and are similar to, but not identical with, the American

National Standards Institute (ANSI) A117.1 Specifications for Making Buildings

and Facilities Accessible to and Usable by physically handicapped people (1980).

Provisions of these two documents are discussed in detail, as they relate to

communication systems for disabled users of buildings.

viii
1 . GENERAL INTRODUCTION

Communication systems in buildings are designed to provide both emergency and

directional information to all building users. Yet, such systems which typically consist of visual signs and audible alarms, may fail to communicate with

vision and hearing-impaired users. As a result, a number of alternative

communication systems have been proposed and incorporated into accessibility

guidelines. These include tactile warnings and indicators, raised or incised

alpha-numeric characters, pulsed visual alarms, high contrast signs, audible

alarms, and specialized acoustic equipment. In many cases, however, the effectiveness of the proposed alerting and signaling systems has not been adequately

determined for the intended user group.

In the following pages the research base for building communication system

requirements for disabled users is examined in terms of three separate sensory

modalities — vision, audition, and touch. For each modality the current code

provisions, specifically the ATBCB Rule (1981), the ANSI A117.1 (1980) Specifications for Accessibility, and relevant local codes are examined. The adequacy of the research base for each provision is then discussed in some detail.

Finally, conclusions for needed additional research in each area are drawn.

Throughout this report the focus will be on the properties of the built

environment that are amenable to improving communications with disabled users.

The many special systems available to expand the user's capabilities are outside the scope of this report and are not discussed.

Although the communication system requirements are specifically aimed at

disabled users, it is important to point out that such systems can affect all

building users. Requirements of populations which differ from the target population must also be considered. Tactile warnings that impede those in wheelchairs or walkers can themselves become a barrier, for example. On the other

hand, provision of effective tactile egress markers could aid all building

users, disabled or not, during a fire or a similar building emergency where

visibility is greatly reduced. As a result, communication system requirements

must be assessed for a wide spectrum of users. The potential for improving

communication for all building users, while meeting the needs of specific disabled users, is great.

1
2 . INTRODUCTION TO VISUAL COMMUNICATION REQUIREMENTS

Visual communication systems in buildings serve two general purposes. First,

they provide orientational and instructional information regarding the interior

plan or layout of a building, the location of particular rooms, activities,

people, and facilities, and the operation of devices such as telephones and

elevators. Information of this type is usually conveyed through the use of

signs incorporating words, numbers, and symbols. Second, visual communication

systems warn building users of emergency situations such as fires, generally

through attention-getting devices such as flashing lights. Most visual com- munication systems — whether designed to transmit emergency or nonemergency

information — make use of techniques such as color coding, brightness

contrast, and standardized locations to increase their effectiveness.

In general, visual communication aids serve nearly all persons disabled or not.

There are, however, within the total population of building users certain groups

for which the potential benefit from the use of appropriate visual aids is

great. These groups include; the visually impaired, including many persons

who are legally blind; persons who are deaf or have a severe hearing impairment; developmentally disabled persons; and those who are illiterate or speak a foreign language.

2.1 VISUAL IMPAIRMENT

2.1.1 Definitions and Extent of Visual Impairment

Three degrees of visual disability may be identified (Bureau of Census, 1979);

(1) Visual impairment includes "blindness in one or both eyes, cataract,

glaucoma, color blindness, detached retina or other condition of the

retina, or any other trouble seeing with one or both eyes even when

wearing glasses."

(2) Severe visual impairment is defined as "an inability to read ordinary

newsprint with glasses using both eyes, or having no useful vision in

either eye, or blindness in both eyes."

(3) Legal blindness is defined as "visual acuity for distant vision of 20/200

or less in the better eye, with best correction, or widest diameter of

visual field subtending an angle of less than 20 degrees."

Using these definitions, in 1972 there were approximately 10.7 million visually

impaired persons in the United States (5 percent of the population), 1.5 million persons with severe visual impairment (0.7 percent), and 468,000 persons

who were legally blind (0.2 percent) (Bureau of the Census, 1979).

The age-specific incidence of severe visual impairment in the population is as follows (Murphy, 1975);

2
° 4 percent of persons with severe visual impairment are under age 25

° 8 percent are between 25 and 44

° 23 percent are between 45 and 65

° 65 percent are over age 65, including 22 percent between 65 and 74,

and 43 percent over age 75.

Only 20,000 persons with severe visual Impairment are in the labor force

(American Foundation for the Blind, 1975). This number represents about 1.3

percent of the number of persons with severe visual impairments and about 0.02

percent of the labor force. The data presented above suggest that age is the

primary reason that most people with severe visual impairment are not in the

labor force. Other possible reasons are employer prejudice against the handicapped, and the possible inability of the severely visually Impaired to perform many jobs. Also, it seems plausible, in view of the very small percentage

in the labor force, that existing architectural barriers, such as the lack of

effective visual communication aids, might significantly contribute to the

low employment figure.

Several points should be kept in mind concerning the definitions and the

estimates of visual Impairment. One is that most persons who are legally blind

are sensitive to light, color, and form and can benefit from visual alerting.

In fact, a person with 20/20 visual acuity can still meet the definition of

legal blindness if enough peripheral vision has been lost so that his visual

field encompasses less than 20 degrees. (Certain retinal disorders do, in

fact, destroy peripheral vision without affecting central visual acuity.)

Most persons who are legally blind have acquired blindness rather than

congential blindness. That is, they became blind during their lives instead

of having been born blind. Since only about 10 percent of blind persons use braille (persons with acquired blindess generally do not), signage designed

to aid people with severe visual impairment should also include some other

form of tactile communication, such as raised letters or arable numbers.

A further problem is that the definitions of "visual impairment" and "severe

visual impairment" are rather vague. For example, it is not clear at what

point a person should be considered to be having "trouble" seeing, nor what

"useful" vision is. Also, should persons with only minor color vision defects

be classified as visually impaired?

2.1.2 Types of Visual Impairment

There is no single predominant cause of visual impairment but rather a number

of conditions which affect vision in various ways. Visual disorders may affect

far vision (e.g. myopia), peripheral vision (e.g. early stages of glaucoma),

central vision (e.g. optic neuritis), contrast perception (e.g. cataracts)

night vision (e.g. retinal disorders), or multiple visual functions. The fact

that the visually impaired population includes persons with a wide range of

visual problems suggests that there cannot be one simple solution to the question of how to optimize the design of visual alerting systems. Instead, the use of redundant visual cues (e.g., color coding, shape coding, numerical

coding, and symbols) and appropriate illumination, contrast levels, and

3
character size can help ensure that the message is effectively conveyed to the

greatest number of persons. In this way, persons with a problem in one visual

area of function (e.g., color deficiency) will still be able to use other cues which they can perceive.

2.2 OTHER IMPAIRMENTS

Another group of building users with special visual alerting needs is the

hearing-impaired. According to Laney (1980), an estimated 17 million persons

in the United States have some form of hearing impairment. Of this group, 0.5

million are totally deaf. An especially critical problem is communication with

deaf persons during building emergencies such as fire, when the visibility of

flashing alarms can be restricted or totally obscured. It is not clear whether

deaf persons with otherwise normal sensory capacities require any special

visual aids for nonemergency communications.

The problem for the developmentally disabled, the illiterate, and persons who

speak a foreign language is somewhat different in that conventional visual com- munication systems may be Ineffective because of difficulties understanding a message rather than due to sensory deficits. Graphic symbols accompanied by

color and shape coding can be helpful to such persons. The use of tactile

cueing may also be useful to these person as well as to the visual and hearing

Impaired persons, and will be discussed at length in section 4.

The section which follows examines the adequacy of existing accessibility

standards for visual communication systems in meeting the needs of disabled

building users, as well as those of normal persons. Architectural and Transportation Barriers Compliance Board (ATBCB) provisions for visual alerting are described briefly and compared with provisions in other standards. Research

relating to the various provisions is discussed, and conclusions are presented

regarding the adequacy of the provisions. Specific research directed at

improving the provisions and the technical basis for them is suggested in

Section 4.

2.3 EVALUATION OF PROVISIONS FOR VISUAL COMMUNICATION SYSTEMS

2.3.1 Visual Alarms

If audible alarms are provided, then in addition, provide a visual

alarm device adjacent to or within each exit sign which flashes in

conjunction with audible alarms and operates from the same power

source . (ATBCB Rule, 1981)

This provision is worded similarly to those in ANSI A117.1 (1980), the DoD-Army

Design Guide (1976), the HEW Design Guide (1978), and the Illinois Accessibility Standards (1978). The DoD-Army Design Guide and the Postal Service Standards (1979) allow rotating lights. Strobe lights and pulsating signals are forbidden in some standards (DoD, 1976; HEW, 1978). It is not clear whether or not the ATBCB wording excludes rotating lights (i.e., whether the word "flashes'

refers to electrically flashed lights only or is used in a more general sense

to mean "flashing lights," independent of the mechanism producing the flashes).

4
A fundamental principle of visual signaling is that the conspicuity of a signal

light is maximized by making that light as perceptually different as possible

from its background. There is considerable evidence from laboratory studies

that the use of a flashing light rather than a steadily burning one is an effective means of increasing conspicuity. Bartley (19&l)j for example,

reported that lights which flashed at frequencies ranging from 2-20 Hz appeared

brighter than the same lights shining steadily. Gerathewohl (1953, 1957) con- ducted a series of laboratory studies of reaction time to peripherally viewed

lights and found that a flashing light was more conspicuous than a steadily

burning light when the background consisted of steady lights. Crawford (1962,

1963) found, however, that the presence of flashing lights in the background

decreased the conspicuity of flashing signal lights.

There have also been some studies of the conspicuity of exit signs during

actual building emergencies. Wiley (1972) and Sharry (1974) conducted investigations of occupant behavior during building fires and concluded that the

absence of illuminated emergency exit signs was an Important factor contributing to injuries and loss of life. Other evidence suggests that some additional means of Increasing conspicuity besides merely illuminating exit signs

is needed. Bryan (1956), for Instance, interviewed 38 survivors of a building

fire. One of the questions he asked each of them was: "Did you notice if any

of the doors had exit lights over them?". Bryan reported that "only 1 person

stated that he knew the exit lights were on... 2 persons did not know, and 2 persons thought the exit lights were on, while 33 people said they never

noticed" — including 8 of the policemen and firemen questioned.

The question of whether a flashing exit light is more conspicuous than a rotating light does not appear to have received much research attention. At

a distance, it would not be expected to matter perceptually which kind of light was used, since both would probably appear to be flashing. Under certain

restricted visibility conditions such as smoke, a rotating light might be more effective, since the sweep of the beam could be seen even when a person is outside the beam. The single most important variable determining conspicuity,

however, is effective Intensity. Effective intensity is defined as "the

intensity of a fixed light, which has the same signal effectiveness as the

flashing light in question" (Illuminating Engineering Society, 1964). If a light is of sufficient effective intensity, it does not matter much, it seems,

which type of light if used — electrically flashedor rotating.

2.5.2 Flash Frequency

Flash frequency of visual alarms shall be less than 5 Hz (ATBCB, 1981)

There is agreement among those standards which specify upper limits for flash

rates that 5 Hz is an appropriate maximum (ANSI, 1980; State of Illinois, 1978;

USES, 1979; State of Massachusetts, 1977). With respect to the technical

literature on the effects of various flash rates on visual perception, the

optimum flash rate is less than 20 Hz. At rates above 20 Hz, a flashing light

begins to be perceived as steady, and when this happens, the advantages of

increased conspicuity through brightness enhancement and the Intermittent

quality of the signal are lost. For dim lights, this fusion process may begin

5
at about 15 Hz. Gerathewohl (1953, 1957) Investigated the consplcuity of

flashing light signals at frequencies of 0.3, 1, 2, 3, and 4 Hz for various

contrasts and flash durations. He concluded that for the conditions tested,

the most conspicuous signal was one with a flash rate of 3 Hz, provided that

the light was at least twice as bright as its background. Response times to

lights flashing at 0.3 Hz were about twice as slow as at 3 Hz when contrast was

low. At high contrast levels, response was still nearly 40 percent slower at

0.3 Hz than at 3 Hz. Since Gerathewohl ’ s studies were limited to flash rates

of between 0.3 and 4 Hz, it is difficult to determine from his data what effect

further increases in flash rate beyond 4 Hz would have on consplcuity.

Aside from considerations of consplcuity, flash rates of certain frequencies

should not be used for visual alerting because they can increase the risk of

triggering epileptic seizures and other undesirable reactions in susceptible

persons. Jeavons and Harding (1975) reported data showing the incidence of

adverse photoresponses in epileptic persons at various flash rates. They found

that the risk was greatest at 16 Hz; however, their most Important finding for

present purposes was that even flash rates as low as 5 Hz were associated with

a substantially increased risk of adverse photoresponse. The incidence of such

responses was only 2 percent at 1 Hz, 2 percent at 2 Hz, 3 percent at 3 Hz, 5

percent at 4 Hz, 11 percent at 5 Hz, and 25 percent at 6 Hz. Thus, an upper

limit on flash frequency of 2 or 3 Hz instead of 5 Hz would seem to be safer

for persons with epilepsy.

Current standards do not place a lower limit on the flash rate. However, it is

reported that very slow flash rates of less than 1 Hz are unsatisfactory since

they do not convey a sense of urgency to most people (Howett et. al., 1978).

The evidence for the ineffectiveness of very low flash rates seems to come largely from the practical experiences of users rather than from formal research

studies. However, Gerathewohl (1953, 1957) produced experimental evidence that

response times to lights flashing at 0.3 Hz were much slower than to lights

flashing at frequencies of 1 Hz or more. Most existing flashing signals have

been designed for use at rates of 1-3 Hz (Howett, et al., 1978); emergency

vehicles generally use warning lights with flash rates of about 1.5 Hz.

Although it is not difficult to measure compliance with the provisions for

flashing exit signs as they are currently stated, the wording of these provisions is sufficiently general that a visual alarm could comply with them yet

still not fulfill its intended purpose. More detailed specifications are needed in several areas:

(1) As noted earlier, effective intensity is the most important determinant

of consplcuity. Consequently, a lower limit on this quantity (minimum

effective Intensity) is required to ensure that the light will not be so weak that that it cannot be perceived. It is necessary to consider such

factors as visibility under restricted conditions (e.g., smoke), degree

of visual handicap to be to be accommodated, and maximum potential distance

between the light and the persons to be warned. The light should not be

so bright that it is disabling for persons sensitive to strong light

(e.g., those with cataracts).

6
(2) The upper limit of 5 Hz on flash frequency may be too high. Although

available research data do not allow firm conclusions about the visual

effectiveness of 5 Hz versus lower flash rates, existing signal lights

rarely have flash rates exceeding 2 or 3 Hz. These lower flash rates are also less likely to cause adverse photoresponses in epileptic persons.

(3) A lower limit on flash rate is desirable. Currently, a light could flash

at an extremely slow rate and still be in compliance — even though it

would not serve as an effective warning.

(4) Specifications for other variables, such as contrast, color, and flash

duration, should ideally be included since they affect conspiculty to some extent. Lights used for visual alerting should contrast with the background as much as possible. Furthermore, red lights are subject to less

scattering than blue lights under restricted visibiity conditions, such

as smoke, and may also connote danger.

2.3.3 Character Dimensions

Letters and numbers on sign systems shall have a width-to-height ratio of

between 3; 5 and 1;1 . (ATBCB Rule, 1981)

This provision is consistent with those for alphanumeric character proportion

in both the ANSI (1980) and Illinois standards (1978). At a particular viewing

distance, the legibility of a character with a given width-to-height ratio —

legibility being that quality of the character which allows a person to quickly

and accurately Identify it — depends on the particular character being viewed

and on the angle at which it is seen. The letter "I", for instance, does not

require as much width as the letter "W" , while equal width and height produce

optimum legibility for the letter "0". If a character is viewed at a large

acute horizontal angle rather than straight on, the optimum width-to-height

ratio increases (a wider character is needed). Meister and Sullivan (1969)

report that for projected displays, the character width-to-height ratio should

be approximately 0.75 (3:4), but closer to 1:1 if the display is to be viewed

at large acute horizontal angles. Heglin (1973) reports that experimental

studies have shown that the optimum width-to-height ratio for certain characters appears to be as high as 1.3: 1.0 when the viewing angle is unfavorable.

The range of width-to-height ratios specified by the ATBCB [4] appears reasonable provided that signage is located such that it can be viewed at an angle

close to perpendicular.

Letters and numbers on sign systems shall have a stroke width-to-height

ratio^ of between 1:5 and 1:10 . (ATBCB, 1981)

ANSI A117.1 (1980) also specifies a stroke-width-to-height ratio of between 1.5

and 1:10; Illinois (1978) requires that the ratio be between 1:6 and 1:10.

^ This term should be changed to either "stroke-width-to-height ratio" or "strokewidth-to-height ratio." When "stroke" and "width" are two separate

words without a hyphen, the term appears to mean the width-to-height ratio

of the stroke itself instead of the ratio of the stroke's width to the

letter height.

7
Meister and Sullivan (1969) and Heglin (1973) recommend that ratios of between

1:6 and 1:10 be used.

The optimum stroke-width-to-height ratio varies as a function of several

parameters — primarily contrast, Illumination, and character size. When positive contrast is used (light characters on a dark background), a narrower stroke

width is required than when negative contrast is used (dark characters on a light background). This is even more true when there is a visually impaired

observer or when less than optimum viewing conditions are present, such as dust

or smoke between the observer and the sign. The effect of these circumstances

is to Increase the apparent dispersion of the light areas of the sign into the

dark areas, thus making the light areas appear larger than they actually are. When high contrasts are maintained between the characters and their background,

Heglin (1973) recommends stroke-width-to-height ratios of 1:6 to 1:8 for black

on white and 1:8 to 1:10 for white on black. When contrast values are low, as they would be if the reflectances of sign colors differed much from those of

black and white, a stroke-width-to-height ratio of about 1:5 should be used

(1973). Similarly, as illumination is decreased, thick letters (1:5) become

more readable than thin ones, regardless of whether contrast is positive or negative. For illuminated characters on a dark background, Meister and Sullivan

(1969) and Heglin (1973) report that thinner strokes (ratios of 1:8 to 1:10)

should be used. When the characters on a sign are small or must be seen at a great distance so that the visual angle is small, relatively thicker letters

and numbers are required (Meister and Sullivan, 1969). Heglin (1973) recommends

a stroke-width-to-height ratio of 1:5 to 1:6 under such conditions.

The range of ratios specified by the ATBCB (1981) is generally consistent with

those recommended by researchers in the field. However, since the optimum

stroke-width-to-height ratio varies considerably for different viewing conditions, more detailed specifications of ratios might be desirable. It should

be made explicit, for instance, that ratios at the 1:5 end of the range should

be used for restricted viewing conditions (low contrast, low illumination

levels, reduced character size) and for signs using negative contrast, while

ratios at the 1:10 end of the range should be used when optimum viewing conditions are present or positive contrast is used. When the characters on a sign

are small or must be seen at a great distance so that the visual angle is small,

relatively thicker letters and numbers are required (Meister and Sullivan,

1969). Heglin (1973) recommends a stroke-width-to-height ratio of 1:5 to 1:6

under such conditions.

2.3.4 Character Contrast

Letters and numbers on sign systems shall contrast in value with

their backgrounds, preferably light letters on a dark background

(ATBCB, 1981).

This provision is worded very similarly to those in other guides and standards

(ANSI, 1980; DoD, 1976; HEW, 1978; Illinois, 1978). As mentioned earlier, contrast may be either positive or negative. For visual tasks involving prolonged

reading of text, it has been found (Tinker, 1963) that black on white (negative

contrast) is more effective. However, some studies have shown that for visual

8
tasks involving primarily detection, positive contrast leads to faster and more accurate response (Bishop and Crook, 1961; Hilgendorf and Milenski, 1974;

Wagner, 1975).

The brightness contrast between characters and background is a potentially more effective coding dimension than the hue contrast (Roth and Finkelstein, 1968).

However, redundant visual coding using both hue contrast and brightness contrast can enhance performance beyond what can be achieved by using either

coding dimension by itself. McLean (1965), for instance, found that adding hue

contrast to brightness contrast on a speed-of-reading dial task led to faster

reading times than did brightness contrast alone.

In order for the current provision to be enforceable, the terms "light", "dark",

and "contrast" must be quantitatively defined. This could be accomplished by

specifying that there be a certain minimum ratio between the luminous reflectances of the characters and their background. Restrictions on the combinations

of colors allowed for characters and background would help ensure that signs

could be read easily by color deficient persons.

Letters and numbers on sign systems shall have a matte finish on a matte

finish background (ATBCB, 1981).

The problem of glare is usually touched upon only briefly, if at all, in

accessibility standards. Illinois (1978), for instance, states that "signs

shall have glare free surfaces which will not interfere with legibility." It

further noted that increased illumination levels to aid the visually impaired

can also increase glare from highly reflective surfaces.

Defining the term "matte" in such a way that it would be susceptible to

quantitative determination could strengthen the enforceability of this provision. This would involve specifying limits for diffuse and specular surface

reflectance. There has been relatively little research on quantifying the

visual impact of reflections from specular surfaces (lES, 1981). One possible

approach to the problem would be to specify levels of illumination in sign

areas in terms of Equivalent Sphere Illumination (ESI). That is, require that

lighting environments produce task visibility equivalent to that produced by a particular level of illumination in a reference sphere. This approach is discussed in detail in the lES Lighting Handbok (1981).

2.3.5 Character Size

Current ATBCB signage requirements state (1981), "Provide numbers and letters

that are between 5/8 inch (16 mm) and 2 Inches (50 mm) high." Since these

requirements apply to raised or incised letters, which may serve as either a visual or a tactile means of communication, both minimum and maximum heights

are necessary. For visual alerting purposes, however, only the minimum character height is of concern. The ATBCB requirements also specify minimum character heights of 1/2 inch (13 mm) and 2 inches (50 mm) for elevator car position

indicators and door jamb markings, respectively. The 5/8 inch (16 mm) minimum

height for raised or incised characters is generally consistent with other

accessibility standards (ANSI, DREW, Illinois, USPS) although slightly higher

9
and lower values are also found. For example, (1/2 inch (13 mm) is used by

Ohio (1977) and 3/4 inch (19 mm) by New Jersey (1977)).

The crucial questions to be asked here are, "What is the intended viewing

distance?", and "What degree of visual disability is to be provided for?".

Under good illumination^ characters 5/8 inch (16 mm) high can be read at a distance of approximately 37 feet (11 m) by a person with normal (20/20) visual

acuity. A person with 20/40 vision would need to be about 18 feet (5.5 m) from

the sign before he could read it, and a person with 20/200 vision (bordering on

legal blindness) would have to be about 3.7 feet (1.1 m) from the sign. Even

though this latter distance seems rather close, it is still further away than

necessary for tactile perception of the sign message, and would allow for

visual perception by all but the most severely visually disabled persons.

2.3.6 Sign Location

The ATBCB requirements specify that interior signage be located on the latch

side of the door^ at a height of between 4 feet 6 inches and 5 feet 6 inches

(1.4 m and 1.7 m) above the floor. This range is similar to those found in

other accessibility standards. ANSI A117.1 (1980) does not specify sign locations, while the DoD (1976) and Postal Service standards (1979) specify ranges

of 3 feet 4 inches to 4 feet 4 inches and 3 feet 6 Inches to 4 feet 6 inches

(1.0 m to 1.3 m and 1.1 m to 1.4 m) , respectively. For visual purposes, signs

should ideally be located perpendicular to the viewer's normal line of sight.

Significant deviations in viewing angle in either the horizontal and vertical

direction exceeding about 30 degrees and 10 degrees, respectively, can decrease

sign effectiveness (Meister and Sullivan, 1969; Heglin, 1973; Sorenson, 1979).

Locating signage within these viewing angle limits is also desirable to accom- modate persons with restricted head movement or peripheral vision. The sign

heights specified by the ATBCB would appear to allow most persons to view the

signs at a viewing angle within desirable limits.

2.4 CONCLUSIONS AND SUGGESTIONS FOR FURTHER RESEARCH

Existing accessibility standards could be improved by providing more detailed,

quantitative specifications in several areas. These areas include:

° Establishing minimum values for the effective Intensity and flash

rate of exit signs. A lower maximum flash rate should also be

considered.

° Specifying stroke-wldth-to-height ratios in terms of expected viewing

conditions when possible.

° Quantitatively defining the terms "light" and "dark" as they are used

in connection with sign contrast.

2 More precise wording is desirable here. The phrase "latch side of the door"

should be replaced by "side of the door that opens first (or closes last),"

because swinging doors and sliding doors do not always have latches.

10
° Restricting color combinations used on signs to avoid loss of contrast

for the color deficient.

° Specifying quantitative limits for specular reflectance of sign

surfaces (gloss).

Some topics needing further research are:

° How do disabled persons behave during building emergencies?

° What criteria and methods of study should be used to evaluate the

effectiveness of visual communication systems for the disabled?

° How do flash rate, flash duration, color, and location combine to

influence conspicuity of visual alarms under normal and adverse

viewing conditions?

° What is the best way of alerting deaf persons during building

emergencies?

° What are the effects of energy-efficient light sources on the

perception of sign color by normal and visually impaired persons?

° What is the visual impact of various amounts of glare on visually

impaired persons?

° What combinations of redundant visual cues are the most effective

(e.g., color, shape, and numerical coding)?

° What are optimum levels of illumination for sign areas for visually

impaired persons?

° What combinations of sensory cues (visual, auditory, tactile) are most effective for the entire disabled population?

11
3. INTRODUCTION TO AUDITORY COMMUNICATION REQUIREMENTS

Although auditory communication systems in buildings are used for both emergency

and non-emergency situations, an individual with a hearing impairment may not

be able to use them. The types of systems of concern for the hearing-impaired

can be viewed in three general categories; (1) warning systems (alarms) which

are primarily for emergency alerting purposes, (2) distributed speech communication ("public address") systems which can serve both emergency and non- emergency functions, and (3) sound reinforcement systems which are used to

amplify and project speech and music over a specific audience area. Though the

degrees of fidelity required by speech communication systems and sound reinforcement systems may differ, the principles applied to achieve a requisite

degree of speech intelligibility are similar. Therefore, major emphasis will

be placed on the discussion of speech communication systems, with several brief

comments pertaining to sound reinforcement.

The first category, warning systems or "alarms", has as its primary function,

the task of alerting building occupants that some dangerous condition exists.

In setting standards for such systems the needs of the hearing-impaired individuals must be taken into account. One must determine whether or not most individuals can in fact hear the alarm, and estimate to what extent such auditory

alarms must be supplemented by visual alarms and/or speech communication

systems

The second and third categories, however, are more complicated because more

than mere detection of a warning sound is required. Information must be con- veyed to the listener. The degree of accuracy achieved in this transmission

serves as the criterion for the system.

Improvements in speech communication systems can benefit nearly all building

users since Improvements in transmission qualities required for hearing-impaired

individuals tend to enhance the quality of such systems for non-impaired individuals as well. Therefore, it seems quite reasonable that standards developed

for public use systems could benefit from technical consideration of the

requirements for communicating with hearing-impaired individuals.

3 . 1 HEARING IMPAIRMENT

3.1.1 Definitions and Extent of Hearing Impairment

Hearing impairments identified during audlologlcal examinations are stated

by comparison (in decibels, dB) to the standard reference zero, ISO 389-1975(E),

which specifies the "normal" threshold of hearing as a function of frequency.

For convenience, hearing Impairments are given a single number representation

as an average hearing loss (AHL) which is the arithmetic average of the losses,

expressed in decibels above standard zero, at 500, 1000, and 2000 Hz, the

frequencies most important for speech intelligibility.

Estimates of the extent of the population affected by hearing impairments

(Plomp, 1978) taken from five U.S. National Health Surveys (NCHS 1965, 1967,

1970, 1975, a,b) suggest that 7.5 percent or approximately 17 million persons

12
in the U.S. experience hearing difficulties. (For a review of population

estimates of hearing-impaired individuals, see Laney, 1980.) Four degrees of

hearing impairments identified by Beasley (1940) were examined by Plomp. A

summary of this study appears as table 1.

Table 1. Estimates of the Population Distribution Average Hearing

Loss (AHL) at 500, 1000, and 2000 Hz in the Better Ear,

for Four Stages of Hearing Disability Classified by

Degree of Auditory Handicap (After Plomp, 1978).

STAGE UNDERSTANDING SPEECH AHL(dB) POPULATION IMPACTED

1 Noisy Environments 24-34 4.1% ("' 9.3 million*)

2 Close range conversation in quiet

35-54 2.4% (~ 5.4 million)

3 Loud speech without

hearing aid

55-89 0.8% (~ 1.8 million)

4 Total deaf > 90 0.2% (~ 0.5 million)

* Based on population of 226 million.

Although persons of all ages can be affected by such hearing impairments, the

incidence and severity clearly Increase with age. Plomp estimates that the

number of persons affected by each of the first three stages of hearing loss

doubles in the following fashion: stage 1 every 10 years from 1 percent of

the population at age 20; stage 2 every 7 years from 1 percent of the population at age 50; and stage 3 every 5 years from 1 percent of the population at

age 55. This Increase in the number of persons experiencing such hearing

disabilities is in addition to the gradual loss of high frequency hearing with

age (presbycusis) that impacts nearly twenty-five percent by age 65 and fifty

percent by age 75 (Duquesnoy and Plomp, 1980).

3.1.2 Types of Hearing Impairment

Hearing losses, among the 17 million persons with greater than 24 dB AHL, have

two additive components (Plomp, 1978). The first component has been classified

by Plomp as a class-A or attentuation loss which can be compensated for wholly

or in part by hearing aids. The amplification improves speech perception in

quiet environments that are not highly reverberant. The second component, however, is classified as a class-D or distortion loss which cannot be compensated

for by hearing aids. Further, because of a significant decrement in resolution,

the impairment makes the individual particularly susceptible to excess noise

and reverberation in rooms.

13
The consequence of the above for hearing-impaired individuals is that without

special attention to matters of architectural acoustics or alternative remedial

measures, a significant portion of the population experiences difficulties in

understanding speech in public building spaces.

3.1.3 Other Impairments

Another group of building users for whom auditory communication systems are of

particular interest is those who are visually handicapped. Though this group

of individuals would typically not have specific auditory requirements in terms

of detection (alarms) or speech intelligibility (speech communication sytems),

they could benefit from adoption of a standardized, easily recognizable alarm

signal indicating that an emergency situation has arisen. This topic will be

discussed later.

The section which follows examines the adequacy of existing accessibility

standards for auditory communication systems in meeting the needs of individuals with a communicative handicap. ATBCB provisions for auditory alerting and

communication are described briefly and research relating to various provisions

is discussed. Research directed at improving the provisions and providing

technical bases for these provisions is then outlined briefly.

3.2 EVALUATION OF PROVISIONS FOR AUDITORY COMMUNICATION SYSTEMS

The most significant formal statement to the inclusion of requirements for physically handicapped individuals in building practices is the American National

Standard Specifications for Making Buildings and Facilities Accessible to and

Useable by Physically Handicapped People (ANSI A117 .1-1980) . The provisions

of ATBCB 's Minimum Guidelines and Requirements for Accessible Design (Part

1190) are nearly identical. Though California and Nevada building codes also

include specifications for auditory communication systems, they do not differ

significantly from ANSI A117.1 (1980). Thus, their provisions will not be discussed individually. Rather, this document reviews only those sections of

ANSI A117.1 (1980) relevant to auditory communication systems.

Relevant sections of ATBCB Part 1190 appears in brackets, and are listed in

their entirety as table 2.

3.2.1 Audible Warning Systems (Alarms)

3. 2. 1.1 ANSI A117. 1-1980, Section 4.28.2, Audible Alarms [119.0180]

If provided, audible emergency alarms shall produce a sound that

exceeds the prevailing equivalent sound level in the room or space

by at least 15 decibels or exceeds any maximum sound level with a duration of 30 seconds by 5 decibels, whichever is louder. Sound

levels for alarm signals shall not exceed 120 decibels.

14
Table 2. ATBCB Part 1190 — Minimum Guidelines and Requirements

for Accessible Design

119.180 Alarms.

(b) Audible alarms. Audible alarms shall produce a sound pressure

level that exceeds ambient room or space noise by 15 decibels or any maximum noise level of 30 seconds duration by 5 decibels, whichever is greater.

119.210 Telephones.

(d) Equipment for hearing impaired people. Telephone receivers shall

generate a magnetic-field in the area of the receiver cap. Volume controls

shall be provided in accordance with Subpart C — Scope.

1190.230 Assembly areas.

(d) Listening systems. Provide assembly areas with a listening

system to assist no fewer than two persons with severe hearing loss.

(1) If the listening system serves Individual seats, locate such

seats within 50 feet (15 m) of the stage or arena. Such locations shall

provide a complete view of the stage or arena.

(2) Acceptable types of listening systems include, but are not

limited to, audio loops and radio frequency systems.

15
In general, audible warning systems should, as part of their design and

installation, include consideration of the following: (1) the acoustical characteristics of the physical sound-radiating device (including power spectrum,

frequency response and directivity), (2) the location and spacing of those

devices, (3) the sound transmission properties of the building in which the

system is to be installed, and (4) the background noise levels over which the

signal must be heard. The provision dealing with audible alarms in the ANSI

standard addresses only the last of these four important design considerations

explicitly.

In 1975, the Committee on Hearing and Bioacoustics and Biomechanics (CHABA) of

the National Academy of Sciences in response to a request from the National

Fire Prevention Association (NFPA) proposed a national standard for fire-alarm

characteristics. Their recommendations with regard to item four above have

essentially been followed by ANSI A117. 1-1980. Further, it was CHABA* s recom- mendation that the acoustical characteristics of the signal source, considered

by itself, be unspecified (item one above). This recommendation was made

because the acoustical environment varies greatly from one building to the

next. A suitable signal system should be selected by the building designer to

"penetrate" the existing or projected background sound distribution.

Though this approach is quite reasonable in structures designed for normal

hearing individuals, some explicit frequency range over which the maximum

sound pressure level of a warning device is achieved should be specified to

accommodate hearing-impaired individuals. This will be discussed further in

the next section.

By specifying the level by which the warning signal must exceed the background,

presumably at the "listener position," CHABA was also addressing items two and

three above implicitly. That is, that decisions as to location and spacing of

physical devices, and dealing with the sound transmission properties within the

building are the responsibility of the building designer. '

The approach taken by CHABA and reflected in ANSI A117. 1-1980 represents a considerable improvement over recommendations like those made by the Uniform

Building Code. Thus, the requirements specify only a minimum decibel level

(A-weighted) at a particular distance from the device. Recommendations of

this type address, only incompletely, item one and omit consideration of the

placement of the sound sources and the acoustic properties of the building in

which they are positioned.

A significant aspect not addressed, however, by ANSI A117. 1-1980 is the minimum

absolute sound pressure level required at a "listener position." Incorporation

of requirements similar to British Standard 5839: Part 1, 1980 for fire alarm

systems would be useful. That standard specifies a minimum A-welghted sound

pressure level of 65 dB generally, and in those instances where the alarm must

arouse sleeping persons, an A-weighted sound pressure level of 75 dB at the

"listener position," with all doors closed.

16
3. 2. 1.2 Section A4.28.2 Audible Alarms

This section appears in the appendix to ANSI A117. 1-1980 and as such is not part

of the ANSI Standard.

Audible emergency signals must have an intensity and frequency that can attract attention of individuals who have partial hearing loss. People

over 60 years of age generally have difficulty perceiving frequencies

higher fhan 10,000 Hz. '

This provision would seem to imply that any frequency below 10,000 Hz of an unspecified but "sufficient" intensity would be appropriate to attract the

attention of individuals who have partial hearing loss. Not surprisingly, the

situation is considerably more complex.

Loss of high frequency hearing with age (presbycusis) is not limited to

frequencies above 10,000 Hz. In fact, perception of frequencies as low as 250

Hz has been shown to be affected (Corso, 1976). Usually losses between 250 and

1500 Hz are less severe, with progressively more severe losses in the region

from 2000 to 8000 Hz. This frequency dependent variation becomes more extreme

with increasing age. However, for all age groups, the region between 250 and

1500 Hz would be a region of minimal loss.

Further, those individuals wearing hearing aids will have a specific frequency

region over which their aids provide maximum gain. Two classic studies (Davis

1947 and Medical Research Council Report No. 261, 1947) recommended maximum

gain over a frequency range from 750 to 4000 Hz. Recent data on commercially

available hearing aids compiled at the National Bureau of Standards for the

Veterans Administration (Beck, 1980) indicates that for most types of hearing

aids, maximum gain typically is present in the vicinity of 1000 Hz, the region

most important for speech intelligibility.

A third consideration with regard to frequency specification is addressed by

British Standard 5839 mentioned previously (Butler, 1980). Specifically, that

standard addresses the issue of attenuation of signal levels as a result of

transmission within the building. Typical building partitions including brickwork, gypsum board on wooden studs, concrete and so on, have transmission loss

values that increase rapidly with frequency (Lawrence, 1970). Therefore, in an effort to maximize transmission through such acoustical "obstacles", the

British Standard recommends maximum acoustic output between 500 and 1000 Hz.

Unfortunately, as Butler points out, many warning devices have maximum output

well above this frequency region. Since the efficiency of sound radiation

from a typical source used for alarm systems increases as the square of the

sound frequency, the performance at relatively low frequencies capable of

passing through architectural barriers may be fairly inefficient.

With the above three dominant factors in mind, it appears that the frequency

region between 750 and 1500 Hz, although best suited as the region of maximum

acoustical output for audible alarms, is probably not the region excited by

most alarm systems.

17
Another aspect of alarm characteristics not addressed by ANSI A117. 1-1980 is

the temporal pattern of the acoustical signal. CHABA Working Group 73 (1975)

in their report for NFPA, unamimously recommended adoption of a standard

"temporal profile" for fire alarm signals. Working Group 73 felt that such

standardization v/ould fulfill the requirements that; (a) the signal should be

evident and easily detectable, (b) should be distinctive and clearly different

from a variety of other alarm systems (e.g. emergency vehicles) and (c) should

present minimal problems in terms of adapting existing fire-alarm systems.

Their conclusion was that for the standard fire alarm, the temporal pattern

should consist of an alteration of nominal "on" and nominal "off" presented

repeatedly. Specifically, they recommended that the signal should:

. . . consist of two "shorts" and a "long" repeated regularly.

Specifically, if the on-segment is denoted by an underlined number

and the off-segment is not underlined, then the basic pattern would

be

1 1 ^

4.

If the nominal duration for a segment were 1/2 second, then the

standard signal would be "on" a half-second, "off" a half-second, "on"

a half second, "off" a half second, "on" one second, "off two seconds" and repeat. We would suggest that the nominal on-segments be

between 0.4 and 0.6 seconds, and that the nominal off-segments be

between 0.3 and 0.6 seconds.

The definition of the nominal "on" and "off" state for the signal

is a standardization problem. We recommend that once the signal is

nominally "on" it should achieve some level and fluctuate less than

2 dB from that sound level. Once the "on" state is terminated, the

level of the signal should fall at least 10 dB within 0.1 seconds,

and stay below that nominal "off" level until it resumes the "on"

state. The transition from "off" to "on" should occur within 0,1

seconds. These measurements could be made in a free field,

because, while the numerical values of "on" and "off" would be

Influenced by peculiarities of the acoustic environment (e.g., the

local reverberation), the informative value of the signal would

probably still be preserved.

(Green, et al., 1975)

It should be noted, that the temporal (and frequency) characteristics of a standardized alarm are still a matter of debate. An earlier proposal by NFPA

which described a "slow whoop" siren is still preferred by some authorities.

However, the idea of a temporal pattern signal seems to be gaining support.

One possible modification is to specify groups of three equal short pulses, a pattern compatible with bell systems.

A major source of difficulty in developing standardized audible alarms is the

pronounced lack of direct empirical psychoacoustic data. This issue will be

discussed further in section 3.3. However, until such time as reliable data

18
are available, it would appear reasonable to make recommendations of an "informational" nature in the appendix to ANSI A117. 1-1980 based on current

insights into the best approach to be taken.

It should be noted that an alarm signal following the recommended temporal and

spectral characteristics above, though of Importance for the entire population,

would be particularly helpful in conveying Information about the nature of the

emergency to visually and hearing-impaired individuals and also, because of its

simplicity, persons with language handicaps. This should provide motivation

for increased efforts toward a well thought-out audible alarm standard.

3.2.2 Speech Communication Systems

ANSI A117. 1-1980 does not address speech communication systems directly.

Reference is made, however, to requirements for sound systems in assembly

areas under Section 4.33. Requirements for assembly areas are often based

upon sound reinforcement systems for individuals free of hearing Impairment.

However, for the hearing-impaired, the critical objective of such systems is

intelligible speech communication.

Therefore, consideration should be given to environmental requirements for

speech intelligibility as well. (Note: Such data would be of use in evaluating direct unaided communication between individuals as well as communication

via electroacoustic systems.)

A discussion of speech intelligibility requirements for the general population

and specifically for those with hearing impairments appears in section 3.3.3,

following a review of those provisions of ANSI A117. 1-1980 which address

"assembly area" requirements.

3.2 .2.1 ANSI A117. 1-1980, Section 4.33.6, Placement of Listening Systems

[1190.230]

If the listening system provided serves individual fixed seats, then such

seats shall be located within 50-ft (15-m) viewing distance of the stage

or playing area and shall have a complete view of the stage or playing

area

This provision is quite reasonable and takes clear advantage of the fact that

considerable non-verbal information can be attained at such viewing distances.

Perhaps more importantly, however, is the fact that many hearing-impaired individuals rely upon information from visual speech perception (lipreading).

Taking advantage of skills developed by the hearing-impaired to help alleviate

their communicative handicaps is by far the most cost-effective approach possible and deserves emphasis.

Often, however, when sound systems are supplied in threaters and auditorla,

managers of such spaces feel that the need for close proximity to the stage has

been alleviated. Though this may be true for some individuals, it certainly

does not serve very well the needs of many hearing-impaired members of the

audience. A statement should be made indicating that both placement of

19
individuals where they have good access to visual information and provision of

listening systems are desirable.

3. 2. 2. 2 ANSI A117. 1-1980, Section 4.33.7, Types of Listening Systems

[1190.230]

Audio loops and radio frequency systems are two acceptable types of

listening systems.

Martin (1977) in a review of possible communication systems for the hearingimpaired discussed each of the listening systems mentioned by this provision.

The most widely used system is the inductive loop system. An a.c. magnetic

field is produced by a loop of wire distributed in a room. A hearing aid used

with this system must have an inductive pick-up coil that can be switched into

operation in place of the microphone normally used with the aid. A disadvantage

of the inductive loop is "overspill" or interference from other magnetic fields.

The second system listed by ANSI A117. 1-1980 is the radio frequency system.

This type has been used quite successfully. A more recently developed system

not mentioned by the ANSI standard is the Infrared scattering system. This

type of system eliminates "overspill" problems at what is typically a lower

cost than the radio frequency system. This option should be considered.

(NOTE: The medical Implications of infrared fields is not well understood;

particularly the risk of delayed development of cataracts.)

Inductive loop pick-ups have been used successfully by Individuals with hearing

aids who wish to use pubic telephones. Older telephones had sufficient "stray"

magnetic field to activate hearing aids equipped with such inductive loop facilities. Recent developments by the telephone industry resulted in more efficient

telephone components that no longer leak the necessary magnetic field strength

required for Inductive loop pick-up (Corliss, 1981). As the telephone industry

replaces the older units with new models, the ability of many hearing impaired

individuals to use normal public telephone systems is being diminished. This

issue deserves attention from standardization groups.

3. 2. 2. 3 ANSI A117. 1-1980, Section 4.31.5 (Telephone) Equipment for Hearing

Impaired People [1190.210]

Telephones shall be equipped with a receiver that generates a magnetic

field in the area of the receiver cap. If banks of public telephones

are provided, then a reasonable number. but always at least one, in a building or facility shall be equipped with a volume control.

3 . 2 . 2 . 4 ANSI A117. 1-1980, Section A4.33.6, Placement of Listening Systems

This section appears in the appendix to ANSI A117. 1-1980 and as such is not part

of the ANSI standard.

20
A distance of 50-ft (15-m) allows a person to distinguish performers*

facial expressions.

This Issue has been discussed under section 3. 2. 2.1 of this document.

3 . 2 . 2 . 5 ANSI A117. 1-1980, Section A4.33.7, Types of Listening Systems

This section appears In the appendix to ANSI A117. 1-1980 and as such Is not part

of the ANSI standard.

A listening system that can be used from any seat In a seating area

Is the most flexible way to meet this specification. Earphone jacks

with variable volume controls can benefit only people who have

slight hearing losses and do not help people with hearing aids.

At the present time, audio loops are the most feasible type of

listening system for people who use hearing aids, but people without

hearing aids or those with hearing aids not equipped with Inductive

pickups cannot use them. Loops can be portable and moved to various

locations within a room. Moreover, for little cost, they can serve

a large area within a seating area. Radio frequency systems can be

extremely effective and Inexpensive. People without hearing aids

can use them, but people with hearing aids need custom-designed

equipment to use them as they are presently designed. If hearing

aids have a jack to allow a by-pass of microphones, then radio frequency systems would be suitable for people with and without hearing aids. Some listening systems may be subject to Interference

from other equipment and feedback from hearing aids of people who

are using the systems. Such Interference can be controlled by careful engineering design that anticipates feedback and sources of

Interference In the surrounding area.

These Issues were addressed under section 3. 2. 2. 2 of this document with the

addition of Infrared scattering systems In assembly areas and the use of

Inductive loop pick-ups In using public telephones.

It should be noted that Martin (1977) as well as a number of other researchers

(Flnltzo-Helber and Tillman, 1978; Klein, 1971, Nabelek and Pickett, 1974 a,b;

Plomp and Duquesnoy, 1980) have Identified Improvements In the acoustics of

building spaces as being another "system element" by which communication with

the hearing-impaired can be facilitated. This topic will be discussed

further In section 3.3.3.

3. 2. 2.

ANSI A117. 1-1980, Section A 4.31.5 (Telephone Equipment for Hearing

Impaired People

Other aids for people with hearing Impairments are telephones,

teleprinters, and other telephonic devices that can be used to

transmit printed messages through telephone lines to a teletype

printer or television monitor.

21
3.2.3 Sound Re 3.nf orcement Systems

As previously discussed (section 3.2 and 3.2.2), sound reinforcement systems

that meet the needs of hearing-impaired individuals are simply more elaborate,

coverage dependent (i.e. must service a finite floor surface area occupied by

an audience), speech communication systems. As a matter of practice, it should

be noted that current sound reinforcement techniques (Davis and Davis, 1976)

use speech intelligibility data in their criteria. These criteria provide a reasonably objective and quantitative approach to sound system design and, in

addition, are closely correlated to the users* needs. This topic will be

discussed in further detail in section 3.3.

3.3 SUMMARY/ CONCLUSIONS

3.3.1 Overview of ANSI A117. 1-1980

ANSI A117. 1-1980 addresses only two issues of Importance to the hearingimpaired: (1) relative intensity requirements of "alarm" systems with respect

to background noise levels and (2) limited requirements for "assembly areas"

(i.e. distance to "performers" and a listing of two audio system types used in

theaters and auditoria). ANSI A117. 1-1980 would be improved by a more rigorous

consideration of the parameters critical to audio alerting systems and speech

communication systems. In addition, appropriate emphasis should be placed

upon the fact that each building requires a "system”. These systems are not

add-on features. Rather they require a degree of attention similar to other

building systems early in the building design process. Approached from this

perspective, the costs are minimized and the completed building will succeed

acoustically for both hearing-impaired and unimpaired individuals.

3.3.2 Audio Alerting Systems

The major parameters of audio alerting systems include: (1) acoustical characteristics of the device (power spectrum, frequency response and directivity);

(2) the location and spacing of acoustical devices; (3) the sound transmission

properties of the building; and (4) the background noise levels in the building. Item 3 leads naturally to item 2, which, when combined with data from

item 4, can be used to specify an appropriate acoustical device (item 1) for

the specific needs of a given building. Though a comprehensive guide for this

design process is not currently available, assistance available from professional acoustical consultants should provide satisfactory results.

Of perhaps more immediate relevance to ANSI A117. 1-1980, are performance

criteria needed by the hearing-impaired and other communicatively handicapped

individuals. These include specification of:

(1) sound intensity - (specified at typical listening positions) whichever of

the following is greater:

(a) greater than or equal to an A-weighted sound pressure level of 65 dB

(75 dB in sleeping environments)

22
(b) 15 dB above the prevailing A-welghted equivalent sound level

(24 hours)

(c) 5 dB above any maximum A-weighted sound level that has a duration of

30 seconds or more

(2) sound spectrum - maximum acoustical output should fall between 500 and

2000 Hz (alternatively between 750 and 1500 Hz).

(3) temporal pattern - adoption of a temporal pattern similar to that

recommended by CHABA Working Group 73 (1975).

3.3.3 Speech Communication Systems

As in all auditory communication systems, those designed to transmit speech

intelligibly require consideration of both the source and the path to the

receiver. The acoustic environment effectively modifies the acoustic character

of the signal. The specific demands made upon the system (design goals) are a function of the needs of the expected receivers and their location relative to

the source. Hence, the acoustic characteristics of the building space are an integral part of the system design.

Two types of speech communication systems are of relevance to the hearingimpaired; those which use electroacoustic reinforcement of the source (talker)

and those which do not (person to person communication). Both of these types

depend upon the "path" or acoustical environment in which communication is

attempted

3. 3. 3.1 Statement of the Problem

Current efforts toward the Integration of hearing-impaired individuals into the

"mainstream" of American society (Northcott, 1973) imposes difficulties in the area of speech intelligibility. There has been insufficient attention to architectural acoustics (i.e. the acoustical environment) in many public building

spaces. All ages are affected. As stated previously, approximately 17 million

people in the U.S. experience hearing difficulties that may pose problems in

understanding speech. These stem primarily from class-D or distortion loss

components of their hearing disability (Plomp, 1978). Further, these distortion losses cannot be compensated by mere amplification or hearing aids. Poor

speech intelligibility for the hearing-impaired in public spaces is degraded

further by excessive noise levels and excessive reverberation. Often, too,

there is an Inadequate design of the electroacoustic elements of the system

(Finitzo-Heiber and Tillman, 1978; Klein, 1971; Martin, 1977; Nabelek and

Pickett, 1974 a,b; Plomp and Duquesnoy, 1980).

Though the impact on communication in emergency situations is much more

obvious, speech communication difficulties under non-emergency conditions can

also have profound effects. Davis (1974), in a study of children's performance

in school, observed that hearing-impaired youngsters enrolled in normal-hearing

classes fall increasingly behind in knowledge of basic concepts when compared

to their normally hearing peers. The problem of hearing-impaired children in

23
understanding speech in the classroom has been identified as a possible cause

of such poor performance ( Finitizo-Hieber and Tillman, 1978).

Therefore, architectural acoustic design and the design of electroacoustic

elements of speech/sound reinforcement systems should not neglect the requirements of the hearing-impaired if a "mainstream" philosophy is to be adhered to.

3. 3. 3. 2 Approach to Speech Communication Systems

A comprehensive approach in designing speech communication systems, therefore,

must include consideration of: (1) the receiver (speech intelligibility

requirements), (2) the path (architectural acoustic requirements) and (3) the source (electroacoustic requirements).

Research applicable to these issues has proceeded from two complementary

perspectives during the last decade. Acoustical engineering concerned with

predicting sound reinforcement system performance for normal-hearing individuals developed techniques that combined traditional physical acoustic measurements and architectural acoustic design practices with innovative electroacoustic design procedures that have been quite successful (Peutz, 1974; Klein,

1974; Davis and Davis, 1976).

The second perspective has emphasized basic research on the speech intelligibility requirements of the hearing-impaired at such institutions as the Institute of Perception TNO (The Netherlands), Gallaudet College, and Northwestern

University. This work has emphasized new quantitative techniques: (1) to assess the impact of hearing impairment upon the speech reception threshold

(SRT,) as affected by the acoustical environment (Nabelek and Pickett, 1974 a,b 5 Finitzo-Hieber , 1978), and (2) to characterize the acoustic environment physically, using new measurement techniques that address those aspects of the environment that are critical to speech intelligibility (Houtgast and Steeneken,

1973; Plomp and Duquesnoy, 1980; Plomp and Mimpen, 1979; Steeneken and

Houtgast, 1980).

This work has laid the foundation for establishing speech intelligibility

criteria that can be directly related to architectural and electroacoustic

design methods. An Integration of these receiver, path and source requirements

is necessary to satisfy the needs of both normal and hearing-impaired building

users. An overview of the current state of the above mentioned research

efforts follows.

To date, the most widely used and easily understandable method of ensuring

adequate speech intelligibility in rooms has been the method developed by Davis

and Davis (1976), based on work initiated by Peutz (1974) and Klein (1974).

This method has been used extensively by audio professionals responsible for

adequate speech intelligibility in the design of sound reinforcement systems.

Though the details of the method employed are beyond the scope of the current

discussion, a brief statement will be given here.

24
Peutz established an empirical relationship between certain physical parameters

of the environment under question and the articulation loss of consonants

(AL(,Qj^g). AL(,Qns was found to be predictive of an individual's ability to

understand speech in a reverberant environment (often important in large public

building spaces). Specifically, Peutz derived the following relationship:

cons yQ

where: D = distance from the listener to the source (m)

T = the reverberation time of the space (sec)

V = volume of the space (m^)

Q

= directivity factor of the source

The acoustical engineer controls the reverberation time (T) by proper design

of the architectural acoustic elements of the building space (specifically

their absorption characteristics). The engineer can also specify electroacoustic devices (when used) that meet particular directivity requirements.

(Note: A serious impediment, however, is the inadequacy of technical data on commercially available electroacoustic transducers).

As a "practical working limit" for sound reinforcement systems, an AL^q^s of

< 15 percent has been established for normal hearing individuals (Davis and

Davis, 1976). This empirically established criterion is used in combination

with the requirement that the slgnal-to-noise ratio be a minimum of 25 dB.

Though data do not exist for establishing a limit on AL^ons hearingimpaired, many speech communication systems currently in use would not meet

the above limit. Therefore, adoption of the above limit in combination with

signal-to-noise requirements could be used to greatly improve speech intelligibility generally, and for the hearing-impaired particularly.

Specific approaches to speech intelligibility requirements with regard to the

hearing-impaired has been undertaken, as mentioned, by researchers affiliated

with the Institute of Perception in the Netherlands. Houtgast and Steeneken

(1973) developed a new physical acoustic measurement technique for characterizing room acoustics called the modulation transfer function (MTF). The MTF

of a space when converted mathematically to a speech transmission index (STI) was found to correlate well with observed speech intelligibility (speech reception threshold, SRT) observed in that space (Duquesnoy and Plomp, 1980;

Houtgard, et al . , 1980; Plomp, et al . , 1980). The results of this research

effort initiated a data base on acoustic criteria to serve the hearing impaired

(Duquesnoy and Plomp, 1980; Plomp and Duquesnoy, 1981). Though current efforts

toward using the MTF technique directly are at the research level, data have

become available suggesting that the reverberation time (T) acceptable for

normal-hearing listeners must be reduced to provide acceptable communication

for hearing-impaired individuals and must be related to the degree of distortion loss (class-D) experienced = 0.75^T, where D is the distortion

loss expressed in dB).

25
Fundamental research continues on the relation between the MTF technique and

speech intelligibility requirements. The development of state-of-the-art measurement instrumentation and methodologies to characterize rooms acoustically

is the next step toward the application of insights derived from the emerging

data.

Research at the National Bureau of Standards is currently directed toward

physical acoustic room characterization. One aspect of this effort includes

(a) the development of an absolute sound power source (Cook, 197 ) and (b) the

development of a modulated reverberation (MR) technique to improve upon traditional decay curve reverberation time measurements. At this time the research

is focusing on a methodology for the accurate determination of sound absorption

coefficients of acoustical building materials. This involves the measurement

of phase angle changes imparted by a room on the infrasonic modulation (below

20 Hz) of the source output. The modulation transfer function (MTF) technique

used to predict speech intelligibility in a room could be developed as an extension of the same system. The MTF is derived by observing amplitude

changes imparted by a room on such an inf rasonically modulated signal.

3. 3. 3. 3 Economic Considerations

The cost of improving communication systems in buildings in general, and to

accommodate the needs of handicapped Individuals in particular, must be controlled. Recently, a method has been developed at the National Bureau of

Standards (Weber and Rudder, 1981) for estimating the costs of alternative

ways of achieving target levels of sound isolation (both outdoor-to-indoor and

between building spaces). Though the acoustical techniques employed for sound

isolation differ from those used to control reverberation time within building

spaces, the same economic model (or cost analysis method) is applicable to the

latter as well.

Further development of the cost-benefit analysis technique for application to

the selection and use of sound absorptive building materials would be very

useful. Though system designs employing appropriate electroacoustic and architectural acoustic elements are not expected to be prohibitive due to costs, a quantitative method for predicting those costs and for making decisions among

alternative designs is essential in meeting auditory communication requirements

for the hearing-impaired.

3.4 FURTHER RESEARCH

Additional research is needed in nearly all areas addressed thus far. At

present, none of the issues has been resolved adequately. However, there are several areas in which simple experiments would prove very effective.

(1) A comprehensive approach to audible alarm systems is needed. Psychoacoustic data on what constitutes an adequate acoustic "alarm" for all

building users including the hearing-impaired are particularly needed.

Design techniques that will assure delivery of that acoustic signal to

building occupants must then be worked out based upon these data.

26
(2) Speech intelligibility requirements for hearing Impaired building

users must be integrated into a single set of criteria and design

methods that can be used to achieve adequate speech communication

systems

(3) Practical physical acoustic measurement Instrumentation must be

developed. Methodologies for characterizing the acoustic environment

of building spaces (e.g. MTF and MR) in ways that are meaningful to

the building design process must be worked out.

The impact of such research is not limited to the approximately 17 million

individuals experiencing communication difficulties due to hearing losses.

Everyone who uses public buildings is affected by the quality of the communication capabilities achieved.

27
4. INTRODUCTION TO TACTILE COMMUNICATION REQUIREMENTS

Tactile communication systems are used in buildings to provide both directional

and hazard warning information primarily to visually handicapped individuals.

These systems typically rely upon raised letters, surface markings, and marked

doorknobs to communicate relatively brief bits of information to visually

handicapped individuals. Information systems, for example, which provide

directional and locational information within a building, are intended to

guide a person. Hazard warning systems on the other hand, are intended to

stop or slow down a person before the hazard is encountered. Thus, intersections, elevators, stairs, excavations and the like must be marked with a clearly identifiable warning message to prevent accidents.

Typically, directional and general information sytems are designed to be sensed

by the fingers or hand. They are located on vertical surfaces often at about

eye level, although there are no consistent requirements for location. These

systems use alphanumeric or Braille characters to convey information, although

one researcher, Genensky (1980), has proposed the use of shapes for encoding

"men's" and "women's" restrooms.

Hazard warning systems are usually located on horizontal surfaces and are designed to be sensed with the feet or a cane. An exception is a knurled or roughened doorknob used to indicate the door to a hazardous area and which is

sensed by the hand and fingers. The hazard warning, typically not specific

in content, indicates the presence of a hazard but gives no additional

information about the nature of the hazard.

An area of tactile communication which has received little code attention is

that of providing emergency information such as fire egress. No provisions

currently exist for indicating fire exits, routes, and safe havens with any

sort of tactile code. Yet, because of smoke layering and obscuration during

building fires, all building users can become visually handicapped during a fire. Emergency tactile guidance systems thus have the potential for providing

essential egress information to all users.

4.1 CODE REQUIREMENTS

Both the ANSI A117.1 Standard and the ATBCB rule address requirements for

tactile communication. These are presented in table 3 and figure 1 which

present the requirements in each area for each code. These requirements cover

the areas of information signage and tactile warnings. Emergency egress inf or mation is not addressed. Table 4 also Includes similar information from a variety of state codes.

28
ATBCB

ELIMINATED

Table 2. Code Requirements for Tactile Warnings

ANSI A117.1 - 1980

4.29 TACTILE WARNINGS

4.29 Tactile Warnings

4.29.1 General. If tactile warnings are required, they shall comply with 4.29.

4.29.2* Tactile Warnings on Walking

Surfaces. Tactile warning textures on walking surfaces shall consist of exposed

aggregate concrete, rubber, or plastic

cushioned surfaces, raised strips, or grooves. Textures shall contrast with

that of the surrounding surface. Raised

strips or grooves shall comply with

Fig. 40. Grooves may be used indoors only.

4.29.4 Tactile Warnings at Stairs. All

stairs, except those in dwelling units,

in enclosed stair towers, or set to the

side of the path of travel, shall have a tactile warning at the top of stair runs

(see Fig. 41).

down.

Fig. 41

Tactile Warning at Stairs

4.29.5* Tactile Warnings at Hazardous

Vehicular Areas. If a walk crosses or adjoins a frequently used vehicular way,

and if there are no curbs, railings, or other elements detectable by a person who

has a severe visual impairment separating

the pedestrian and vehicular areas, then

the boundary between the areas shall be

defined by a continuous 36-in (915-mm)

wide tactile warning texture complying

with 4.29.2 (see Fig. 42).

29
Tactile Warnings - Table 2 continued

4.29.6* Tactile Warnings at Reflecting

Pools. The edges of reflecting pools

shall be protected by railings, walls,

curbs, or tactile warnings complying

with 4.29.2.

4.29.7* Standardization. Textured

surfaces for tactile warnings shall be

standard within a building, facility,

site, or complex of buildings.

A4.29 Tactile Warnings

A4.29.2 Tactile Warnings on Walking

Surfaces. Warnings set slightly more

than one pace (24 in to 48 in (610 mm

to 1220 mm)) in front of a hazard

allow a blind person to perceive the

signal, follow through with one last

step, and stop before encountering

the hazard. People who use long canes will usually detect a textured surface

with their cane before they detect it

with their feet.

A4.29.3 Tactile Warnings on Doors to

Hazardous Areas. Tactile signals for

hand reception are useful if it is

certain that the signals will be

touched

A4.29.5 Tactile Warnings at Hazardous

Vehicular Areas. Curbs on sidewalks

serve as customary tactile cues for the

edge of a street. The abrupt change in

level is easily perceived by cane or foot

A4.29.6 Tactile Warnings at Reflecting

Pools. Other hazards besides reflecting

pools may require similar protection.

A4.29.7 Standardization. Too many

tactile warnings or lack of standardizati

weakens their usefulness. Tactile signal

can also be visual signals to guide dogs,

since dogs can be trained to respond to a large variety of visual cues.

30
Figure 1. ANSI A117.1 (1980) Diagram of tactile warning at

hazardous vehicular areas

31
Table 4. Tactile Warnings for Horizontal Surfaces from Other Codes

GSA

- use short staccato cue, such as several rows of brick across sidewalk

to cue danger (such a stair, direction change etc.) perpendicular to

line of movement — cue should be rougher than surrounding texture

- use design, planting and paving to indicate direction of access,

changes in level and slope, intersection and adjacent areas/facilities

“ narrow strips of texture — 4 '-18" width = danger

wide strip — 36" minimum to signal adjacent areas and facilities

DoD

- provide textured warning strips (e.g. paint-on gritted epoxy) on walk

or floor perpendicular to head of stairs, ramps (except curbside)

and other hazards

- strips should be 1/16" high, 3" wide with 3" intervening spaces and

36" long — in contrasting color (safety yellow)

use strips of vinyl or rubber in carpeted areas

Illinois

provide tactile warning signals of consistent texture within building

or site use only as an alert

- pattern — (a) applied strips forming grooves 1/8" deep and bonded to

surface

(b) continuous sheet with grooves 1/16" minimum depth

(c) grooves 1/8" deep integral to walking surface

(d) change of material to one with 1/8" deep grooves

width of signal shall be 2'0" perpendicular to grooves if there is a perceivable difference in hardness between walkway and signal and

3*0" if no difference

- 4" wide guidestrips are effective

use cue to indicate hazardous area along with or pedestrian area

Minnesota

- use differences in surface texture to identify ramps and curb cuts

use tactile floor strips to identify abrupt changes in floor elevation

Texas

- use special rough or textured surfaces to signal approaching ramps,

walks intersections

- use curbs to indicate approaching vehicular crossing

Washington

- use tactile cues, textural change of surface, to provide continuity

of directional information, and serve as warning against hazards

HEW

floors at head of open stairs, ramps, curbs should have abrasive

strips or textured flooring material

32
4.2 TACTILE WARNINGS ON HORIZONTAL SURFACES

Only limited research has been conducted on the perceptability of tactile

warning strips in public places. These strips designed to be felt by a foot or

a cane, provide warning of a possibly hazardous transition in the walking surface. Thus, such strips would be located at the head of stairs, at curbside

before a street crossing, at platforms in transit stations, and at similar

abrupt changes in horizontal movement planes.

Assessing the effectiveness of such strips is a difficult task, for unlike most

tactile (psychophysical) research, the users are wearing shoes which reduce

their tactile sensitivity to an unknown and variable degree. If the user is

relying upon a cane, he/she still does not experience direct tactile contact

with the strip. As a result, specification of the adequate stimulus for tactile warning becomes much more complex than simply knowing the sensitivity of

the soles of the feet. Such specification can best be determined behaviorally

by assessing the area, surface characteristics, and extent of surface change

of the strip that a significant number of visually impaired persons wearing

specified or known foot gear can detect reliably.

Aiello and Steinfeld (1979) conducted a three phase study designed to determine

some of the problems that the visually impaired face during movement through an unfamiliar set of buildings. In the first phase, 28 visually handicapped

people walked a specified route using recorded directions in a university

building which required the use of a variety of orientation cues. Observers

differed in their degree of visual handicap, with at least half being partially

sighted with some degree of color, light, and/or object perception. As a result, the variations in color contrast were studied along with the tactile

variables. A set of recorded directions were given to participants at the

beginning of each of five segments of a specific route. An observer noted all

directional and environmental problems and recorded the time to complete the

walk. The participants, who required an average of seven minutes for the walk,

completed both a map and a questionnaire at its end. They noted three major

problems: disorientation and confusion due to large areas and irregular paths,

hazardous and difficult negotiation due to obstacles, and poor directions.

Phase two, which used eight participants from phase 1 in a laboratory project,

was designed to explore variables in the design of tactile warning signals

Walking performance parameters such as pace gait (feet/minute) and stopping

distance (after a tactile signal was felt) were assessed to determine baseline

performance. Next, the minimum raise (height) detectable by either cane or feet was determined. Finally, parameters related to configuration such as abrasive strips, abrasive areas, small area ribbed rubber mats and large area

ribbed rubber mats were assessed. Raise varied from 1/64-1/8 inches. Observers

noted cane technique, sensing method (feet or cane), and signals detected.

Preference data were also obtained. Participants strongly preferred the larger

area rubber matting because of its greater area, texture, resillancy, and

distinctive sound characteristics. Review of the results from the eight subjects suggested that raise height should be no more than 1/8 inch but should

be at least 1/16 inch. Heights greater than 1/3 inch may become tripping

hazards (although such heights were not examined in the present experiment).

33
Larger areas seemed to be preferred particularly if patterned or roughly

textured. Signals which contrasted in resiliance (and color) with surrounding

floor surfaces also appeared to be more effective. The critical issue was

depth, or the distance between the tactile cue and the signaled hazard, for

which these authors recommended 18-36 Inches, partly because the average

stopping distance (after detection of a tactile cue) was 2.82 feet with a range

of 1.1 to 4.0 feet. Observation also indicated that the diagonal cane technique yielded much shorter stopping distances. The authors recommended that

signal placement be removed by an intervening area from the staircase hazards.

This area should, however, be colored the same as the hazard to focus attention

on the hazard and not on the signal.

Only four types of tactile surfaces were assessed in this experiment—masking

tape layers, abrasive strips, areas of an unspecified material, and ribbed

rubber mats (with ribs perpendicular to the line of travel). Footgear of the

participants was not recorded. Tactile cues were tested only for level sur- faces—no staircases were involved. Use of visual cues was not examined separately for the partially sighted participants. Only three levels of raise were assessed, 1/64, 1/32, 1/8 inches. Measurements of floor resiliance were

not taken nor was the patterning of the resiliant material specified or varied.

Subjects were familiarized with signals before the experiment began and told

the general type of configuration to expect for each experimental session.

In phase three the recommended tactile warnings were tested in an actual

building using five of the participants from phase two. These tactile warnings were Installed at the tops of all staircases and before elevators on two

floors. Raised numerals were also provided on an elevator control panel. Participants were familiarized with both the tactile warnings and the numerals.

Reliance upon the warnings and performance with the numerals were observed and

recorded. Participants again provided maps of the route they followed at the

conclusion of testing. Distance of the tactile cue for the staircases was varied from 18-36". Again an intervening area was left between the cue and the

first step. Results indicated that an 18 inch "signal" was acceptable in most

cases except where a staircase was approached straight on. Here a 24 inch

"signal" would have been more acceptable. (Performance measures were not indicated, however.)

From the assessment of directional indicators, the authors reported that

subjects found the raised numerals on vertical surfaces very difficult to use—perhaps because they had not been trained in the use of arabic characters.

Even so 5 those participants who did use the numerals found them difficult to

read. With practice, their performance improved but they reported that although

the numeral height of 1/2 inch was acceptable, the stroke width of 1/16 inch was too thick. As a result the authors recommended a sharper numeral with a greater stroke width to height ratio.

Based upon the data obtained in this study, Aiello and Steinfeld (1979)

recommended tactile warning strips for stairs in a path of travel, at passenger

loading platforms, and at the intersection of pedestrian and vehicular circulation paths. These strips should take the form of 1/8 inch grooves running

parallel to the hazard edge with a minimum width of 24 inches if there is a

34
change in perceived hardness and 36 inches if there is not. They also

reconunended the use of continuous handrails on staircases with extension of one inch at the top and the bottom. Other recommendations included the use of

tactile signals—roughened surfaces—on door openers for doors to hazardous

areas; as well as the use of raised characters 1/32 inches from the surface an

at least 5/8 inches high or indented characters 1/32 inches deep with a strokewidth of a least 3/8 inches. The authors provided no data to support their

recommendations for handrails or door tactile warnings. They did not discuss

the composition of door tactile warnings either.

Templer (1980) also conducted a study of tactile surfaces for visually impaired

pedestrians. He noted (page 44-45) that "while various types of tactile guides

have been used to aid visually handicapped pedestrians . . . there appears to

have been no attempt to determine experimentally what types of outdoor surfaces

textures are most easily detected by the visually impaired." Templer *s study

was designed to assess the response to a variety of materials and surfaces that

could be added to existing pedestrian pathways.

Templer (1980) selected eleven textured surfaces and a twelfth control surface

(normal sidewalk) for study. Each surface was four feet wide and six feet long

except for one 15 foot long section. The textures varied from thermoplastic

solids, to ruled concrete, exposed aggregate, asphalt, paving brick, and similar

material. Characteristics of each surface are reported by Templer (1980) in

detail. A total of 52 subjects were used, 31 of which were visually handicapped

and legally blind. The remaining 21 subjects were physically, but not visually

handicapped. Visually handicapped subjects included those with low partial

vision, high partial vision, and total blindness. See Templer (1980) for a discussion of criteria for determining extent of visual handicap.

Subjects were initially familiarized with all surface textures. Then, subjects were asked to detect the surfaces one at a time in random order. Their task was

to walk forward from a starting point which was randomly varied from 15 to 22

feet from the textured surface, and to stop immediately upon detecting any

change in the surface. Guide ropes were placed at both sides of the test area. Distance traveled along the textured surface was recorded along with the time

to traverse the last 10 feet of the approach path. If a surface change were

detected, subjects were asked to rate the ease of detection on a four-point

rating scale. The textured surfaces were also evaluated in terms of comfort,

balance and stability for non-visually but physically handicapped persons,

again using a rating scale.

The results Indicated that those subjects with high partial vision detected 85

percent of the test materials. Of the people with low partial vision, 86 percent successfully detected seven of the twelve materials, while 70 percent

detected another three materials. For the totally blind subjects, 86 percent

detected five of the twelve materials while 70 percent detected three additional

materials. Only three materials, thermoplastic strips, exposed aggregate, and

pliant polymer, were detected by more than 85 percent of all visually handicapped subjects. Two of these materials, thermoplastic strips and exposed

aggregate, were also rated as easily detectable by all subjects. Measurement of

stopping distances, recorded for all subjects, indicated that totally blind

35
subjects took longer than those with low partial vision who took longer than

those with high partial vision. All seven materials tested were detected by 90

percent of the totally blind subjects within 48 inches of the start point, and

one, pliant polymer, within 30 inches. Stopping distances ranged from 0-24

inches for low and high partial by sighted subjects. Comfort ratings of the

surfaces by other handicapped subjects revealed that the exposed aggregate surface was rated as moderately or greatly adverse. All of the other materials

received mean ratings in the categories of "not at all" or "a little" effect on comfort, balance, and stability.

Inclusion of users with non-visual handicaps is a very Important consideration

in developing recommendations for tactile surface warnings. Such warnings may

impede movement by the wheelchair bound, crutch, cane or walker users, and cause tripping hazards for all people.

Templer (1980) commented that most visually impaired subjects were able to

detect changes in surface materials studied with little difficulty. Exact

specifications of the physical characteristics of the most effective set of

warning materials still remains, however. For those materials tested, a 30

inch to 48 inch strip of material was needed for detection. Thermoplastic

strips six inches wide and spaced at six inch intervals across the direction of

movement were found to be both detectable and comfortable. These patterns are very different from the ANSI recommendation of 3/4-2" strips separated by 1/4" - 3/4".

The work by Templer and Aiello and Steinfeld represents a preliminary

investigation of the characteristics of tactile surfaces that could be used for

movement guidance and direction finding. Use of both behavioral and preference

techniques appears to be a viable means for assessing tactile effectiveness.

Nevertheless, numerous questions remain to be answered in the field of tactile

warnings. From a research point of view, the number and kind of subjects

studied should be expanded and defined. Visual capacity should be defined con- sistently throughout all research addressed to tactile warnings and communication systems. Age, sex, movement experience, education and similar demographic

variables must be documented and studied. Similarly, tactile deficits if any

should be noted. Use of a cane should be documented along with kind of footgear

worn. Footgear in fact is never mentioned in either study reviewed in this

section; yet it might adversely or differentially affect sensitivity. Finally,

the characteristics of the tactile stimulus should be explored and specified in

terms of material, resillancy, raise, patterning, slip resistance, and contrast

with surrounding materials. Furthermore, the optimum physical dimensions and

application pattern remain to be explored in greater detail. For example,

Aiello and Steinfeld (1979) recommended depths of 18 to 36 inches while Templer

(1980) found depths of 48 inches to be most appropriate for totally blind

subjects. Such discrepancies must be further assessed.

36
4.3 DIRECTIONAL AND INFORMATIONAL CUES

Both the ANSI A117.1 Standard and the ATBCB Rule treat two types of tactile

signage for manual communicating; raised or incised alphanumeric characters and

textured surfaces on door knobs to hazardous areas. Details of the alphanumeric

characters are specified in terms of height (5/8 - 2") width (1/4" minimum) and

depth (1/32"). See tables 5 and 6. Details of the textured warning are less

specific. These warnings may be achieved by knurling, roughening, or applying

materials to the hand contact surface. The issues of consistency in materials

and most effective tactile cues are not addressed by either standard.

37
Table 5. Code Requirements for Tactile Communication

ATBCB Rule

1190.200 Signage

ANSI A117. 1-1980

4.30 -— Signage

(c) Raised or incised characters. 4 . 30 Signage

Provide numbers and letters that 4.30.1* General. All signage that are

provides emergency information or

(1) Raised or incised from the general circulation directions or background surface 1/32 inch identifies rooms and spaces shall

(0.8 mm). Also incise or raise comply with 4.30.2, 4.30.3, and

symbols and pictographs in this 4.30.5. Tactile signage shall also

manner

comply with 4.30.4.

(2) Between 5/8 inch (16 mm) 4.30.2* Character Proportion.

and 2 inches (50 mm) high. Letters and numbers on signs shall

(3) Sans serif with sharply have a width-to-height ratio between

defined edges. 3:5 and 1:1 and a stroke-width-to-

(4) If incised, provided with height ratio between 1:5 and 1:10.

at least a 1/4 inch (6 mm) stroke 4.30.3* Color Contrast. Characwidth

ters and symbols shall contrast with

their background — either light

characters on a dark background or

(b) Character proportion and dark characters on a light backcontrast. Letters and numbers ground

on sign systems shall: 4.30.4* Raised or Indented

(1) Have a width-to-height Characters or Symbols. Letters and

ratio of between 3:5 and 1:1. numbers on signs shall be raised or

(2) Have a stroke width-to- incised 1/32 in (0.8 mm) minimum and

height ratio of between 1:5 and shall be sans serif characters.

1:10. Raised characters or s 3nnbols shall be

(3) Contrast in value with at least 5/8 in (16 mm) high but no their backgrounds, preferably higher than 2 in (50 mm). Indented

light letters on a dark back- characters or s 3nnbols shall have a ground

stroke width of at least 1/4 in

(4) Have a matte finish on a (6 mm). Symbols or pictographs on matte finish background. signs shall be raised or indented

(not clear whether "b"

applies to "c")

1/32 in (0.8 mm) minimum.

38
Table 6. Tactile Communication Requirements from Other Codes

Post Office

- raised/incised letters and numerals required for access

- room or office identification shall be mounted 4' +6" above finished

floor and adjacent to entryway consistently on left or right side of

door

incised letters 1" high, 1/32" deep (minimum)

- raised letters 5/8" high, 1/64" raised (minimum)

HEW

- raised letters/numerals to identify rooms/offices

placed on corridor wall on latch side of doorway approximately 60"

from floor

characters 5/8" high, 1/32" raise (minimum)

door indentif ication — 60" centerline preferred (54-66" range)

Illinois

tactile signage required using raised characters

- raised 1/32", height 2 1/2" (minimum

mounted 4 '-6" - 5'-0" above surface

mounted at latch side of door

Massachusetts

egress signage, raised or recessed — 1/4" minimum height

- braille may supplement, but not substitute

Minnesota

- tactile identification required — raised or recessed,

mounted on wall adjacent to the door on latch sides between 4 ’6"

(1.372 m) and 5'6" (1.676 m)

5/8"-l" (16-25 mm) letters and 2-3" (51-76 mm) numerals raised 1/32"

or recessed 1/8" in roman or arable type

UBC

raised or recessed letters mounted between 4 '6" and 5 '6" on wall

adjacent door handle

39
Table 6 (cont.)

New Hampshire

signs, numbers/graphics for egress should be permanently raised 1/8”

(3 mm) with 1 1/4" (32 mm) minimum height

braille may supplement but not substitute

New Jersey

sign identification shall have raised S 3nnbols 3/4" high mounted 4 '6"

above finished floor on wall nearest door handle when door is closed

- routes of travel shall be similarly marked

North Carolina

signs for identification shall have raised or notched letters/numbers

mounted 4 ’6" - 5 ’6" from floor on side nearest door handle when door

is closed.

Ohio

- raised or incised letters

- raised letters recommended when letter heights between 1/2" (15 mm)

(minimum) and 1" (25 mm) — larger letters may be raised or incised.

- preferred projection from sign face is 1/64' (0.4 mm)

- room or office identification should be mounted at a height of between

54" (1370 mm) and 66" (1675 mm) above floor

Braille may supplement

Texas

- raised or incised letters/numbers should be used for identification

and should be placed to left or right of doorway, on handle side,

about 5' above floor level

Utah

- use raised/incised letters or numerals mounted 4'-6" to 5'-6" above

floor, on side nearest door handle when closed

Washington

use tactile signs with raised or grooved lettering 1/16" with height

not less than 1" or greater than 2"

- do not mount more than 66" above floor, adjacent to strike jamb use to identify openings to public spaces, stairs, loading platforms,

stages, mechanical equipment rooms, fire escapes, elevators,

hazardous areas

GSA

raised letters/numerals preferred; mounted 54-66" with 60" preferred

40
4.3.1 Skin Sensitivity

The first question to be resolved in a consideration of tactile communication

is that of overall skin sensitivity to discrete tactile stimuli.

The sensitivity of the skin has been investigated by studying spatial

responsiveness using methods such as point localization and two point thresholds

and by determining direct pressure sensitivity. In point localization, subjects point to or touch a spot or point on the skin previously touched by the

experimenter (Stevens and Green, 1978). The error of localization between the

two points is measured. Errors in point localization vary from 1.5 mm on the

index fingers to 9.5 mm on the back (Kenshalo, 1978). There is a proxlmodlstant gradient (extremity to trunk) of decreasing errors of localization for

both the upper and lower extremities, with the most sensitive areas being the

fingers, face and hallux (big toe) (Weinstein, 1968). Males and females are about equally sensitive as measured by point localization, although males are slightly more sensitive for palm measurements (Weinstein, 1968).

The two point threshold or "limen" is defined as the smallest separation of two

blunted points presented simultaneously that can be recognized as two distinct

spatially separated touch stimuli (Kenshalo, 1978). Two point threshold measurements are typically four times as large as measures derived from point

localization data (Kenshalo, 1978), even though the procedures used to measure

the two differ only in that localization stimuli are presented successively

while two point stimuli are presented simultaneously. The pattern of response

to two point stimuli is very similar to that for point localization. Essentially, the extremities such as the fingers are most sensitive and areas of

the trunk are least sensitive with a range of value from about 2.5 mm for

mid-finger to 47.0 mm for the calf (for two-point limen measures) and about

1.4 mm for the index finger to 12.5 mm for the back for point localization

measures (Kenshalo, 1978).

Touch sensitivity varies for different body regions according to the method

selected to study sensitivity. While the pattern of response is similar for

two-point and point localization measures, despite the greater sensitivity to

the point localzation, the pattern for pressure sensitivity varies from .5 mg

on the nose, 11.4 mg on the index finger to 36.7 mg on the hallux and 40.3 mg

on the calf (Kenshalo, 1978). Weinstein (1968) who correlated threshold data

from the three measures of tactile sensitivity, pointed out that there were

low non-significant correlations between point localization/ two point measure

and pressure measures but a high (.92) correlation between the two spatial

measures. Thus, the index finger ranked first for point localization but

fifteenth for pressure sensitivity.

For punctate stimuli (passive touch), Kenshalo (1978) reported that the absolute

threshold varies from 0.26 erg on the ball of the thumb to 0.36 to 1.090 erg

for the other fingers. Females tend to be slightly more sensitive than males

for pressure sensitivity (Weinstein, 1968).

Schiff (1980) commented that measures of tactile sensitivity correlate only

moderately with each other even in the same area of skin. He claimed (p. 19)

41
that "Tactual judgments are apparently based on complex phenomena and no single

measure of skin sensitivity is a particularly useful index of any other." Yet

since spatial sensitivity is probably more critical than pressure sensitivity

for tactile communication, it is important to know that both the finger and

halux are most sensitive to measures of object distance.

4.3.2 Visual Impairments and Tactile Sensitivity

The data discussed up to this point have been obtained primarily with healthy,

young adults. There is some evidence that visually impaired observers differ

much more widely in their sensitivity to touch.

For example, Llnkblom and Lindstrom (1976) measured thresholds for passive

touch in both normal and blind subjects. Using 32 subjects, 10 of whom were

blind, they administered short mechanical pulses of about 100 Hz to the finger

pads and varied the skin indentation amplitude of the stimulus pulse.

They recorded the lowest amplitude that subjects reported feeling on 3 to 4

consecutive stimulations. Inspection of the data revealed that thresholds were generally about 30 percent lower with less variation for blind subjects than

for normal subjects, suggesting that the blind may have somewhat greater sensitivity. The greater sensitivity may be due to differences in manual labor, or

to the generally younger age of the blind subjects. The authors also found no difference between fingers, even for those used for reading braille or for

handedness or sex for blind subjects, but did find slightly lower thresholds on

the dominant side for the non-blind subjects.

Heinrichs and Moorhouse (1969) measured tactile thresholds in healthy seeing

subjects, blind, and blind diabetic subjects. Three threshold measures were

obtained; vibratory-perception, light-touch perception, and two-point perception. Although clinical measures do not often demonstrate diabetic loss of

sensitivity (neuropathy) in the hands, the tactile measurements obtained for

the ten diabetic subjects indicated that all perceptual threshold measurements

were higher than for the non-diabetic subjects with no overlap in the threshold

range for the pressure and two-point measurements. Thus, the two-point measure

for the non-diabetic subjects varied from 1.3 to 1.9 mm while for the diabetic

subjects they varied from 2.3 to 2.0 mm. In addition only two of the ten

subjects indicated any awareness of sensory loss in their fingers. The authors

indicated that: "The present study arose from the observation that diabetic

blind persons have difficulty in reading Braille. The findings appear to

explain this fact. Subjects with marked elevation of touch-perception thresholds in their fingertips were scarcely able to feel the type at all. In others

the difficulty was probably caused by their inability to perceive clearly the

individual points. In particular, the threshold for two-point discrimination

ranged from 1.3 to 1.0 mm in the non-diabetic and from 2.3 to 2.9 mm in the

diabetic blind subjects. The standard distance between the points in English

Braille type is 2.2 mm" (Heinrichs and Moorhouse, 1969, p. 74-75).

These findings suggest strongly that spatial separation of communication

elements for the blind should exceed 3.0 mm. What is not known, however, is

the general sensitivity for tactile stimuli of the population of diabetic blind

42
subjects. The ten subjects studied by Heinrichs and Moorhouse were in

reasonably good health with medical control of the diabetic s3nBptoms at the

time of the test. These subjects were also young, with a mean age of 31. As

a result, the threshold measures might be higher for aged or more severely ill

patients, with consequently serious implications for tactile communication

systems

In the U.S. the number of diabetic blind patients is about 5 percent of the

adult legally blind population (Westet, 1976). Furthermore, 46,000 newly

diagnosed cases of eye problems due to diabetes are reported each year, with

90 percent of these cases involving people over 45 and 40 percent over age 65

(Westet, 1976).

4.3.3 Braille Sensitivity

The data discussed on tactile perception thus far relate primarily to passive

perception in which stimuli are applied to the subjects' skin. The subject

typically remains motionless during stimulation. Yet, touch in the real

world is active; the observer moves his hand across objects, setting up much

more complex patterns of stimulation. Kenshalo (1978, p. 48) comments, "But

touch, as experienced in dally life, should be considered as an exploratory

rather than as merely a receptive sense. What little quantitative data exist

indicate that the skin exhibits far greater acuities when used in active

exploration than when used as a passive receptor."

Kenshalo (1978) discussed Braille reading as a task that depends heavily on

active tactile spatial acuity. He commented that the six embossed Braille dots

for a character stand 1 mm above the surface with each dot separated from its

neighbor by 2.3 mm. Legibility for Braille is only moderately reduced when

this space is reduced to 1.9 mm. (Obviously, these data were not derived from

diabetic blind subjects.) If subjects are not allowed to move their fingers or make rapid scanning movements, the ability to read Braille is just about eliminated. Kenshalo (1978) noted further that observers can detect a 1 mm groove

in an otherwise smooth surface, if allowed to move their hands. Similarly,

Lederman and Taylor (1972) and Lederman (1974) reported that the perceived

roughness of a surface is related not only to its physical characteristics such

as groove width, but also to the amount of force applied by the finger. Heimar

(1973, p. 67) commented that "The ability of the fingertips to sense textures

and surface details reflects the skin's capacity to detect patterns which are shifted over its surface (i.e., spatiotemporal cutaneous patterns)." Furthermore, Schiff (1980) commented that the manipulative skill of the observer can

be critical in enabling him to make fine discriminations.

Lappin and Foulke (1973) investigated some of the parameters which might be

manipulated to increase Braille reading speed. Braille is typically read at

about 60/80 wpm while English print is read at 200-400 wpm with 1000 wpm occa- sionally reported for speed readers. Braille readers generally use one finger,

the index finger, to read Braille. Lappin and Foulke consequently studied the use of several fingertips simultaneously to see if information could be procesed more rapidly and accurately this way. Using eight subjects, four blind

and four sighted, Lappin and Foulke had them Identify the number of one-dot

43
patterns in eight successive sets of four patterns, with one to four fingers on

one or both hands. The fastest reading times were obtained when the patterns

were read by two fingers—one on each hand. The authors suggest that use of

separate hands in reading Braille is a fertile topic for further exploration.

4.3.4 Shape Sensitivity

Some research has bee done on the tactile perception of alphanumeric and

geometric shapes. Austin and Sleight (1952a) examined the accuracy of tactile

discrimination for letters, numbers and geometric forms using the index fingertip. They were concerned with determining the maximum number of forms which

could be accurately discriminated.

Two sets of stimulus figures were used in the experiment. ITie first set

contained all the letters of the alphabet, the numbers 2-9, and geometric forms

including a diamond, square, right triangle, equilateral triangle, rectangle,

parallelogram, crescent, semicircle and cross. The first set were cut from 1/4

inch masonite sheeting with each character being the maximum size that could

fit within a 1/2 inch circle. A constant stroke width of 2 mm was maintained

from the letters and figures; the geometric forms were solid. In the second

set the forms were made of wire pins. Thus the forms were made of a series of

points. A total of 43 forms was tested in each of the two sets. Each set was mounted Inside a circular wooden disc which allowed the experimenter to expose

each form individually through a slit.

Subjects were asked to touch each form as it was presented and to respond as quickly as possible indicating to the experimenter what the form was. Both

index fingers were used, alternating every five to ten trials. This procedure

was followed for four conditions—solid forms with no hand movement, solid with

movement, point figure with no movement, and point figures with movement. Ten

adults, five male and five female were tested in each condition for a total of

forty participants in the entire experiment.

The authors report their results in terms of a 90 percent accuracy criterion.

Using this criterion, six letters, C, I, L, 0, T, and U, were reported accur- ately for all four conditions. When no movement of the fingers was allowed,

nine solid and twelve point forms were accurately identified. Clearly movement of the fingers is critical for accurate discrimination. Thus, with solid

forms and movement, almost 60 percent of the stimuli met the criterion. These

included: C, D, E, G, I, J, K, L, 0. P, Q, T, U, V, W, X, Y, 2, 7, 9, diamond

right triangle, rectangle, crescent, and semicircle. Accuracy was not correlated with speed of response, however.

9

Analysis of the error data revealed that common confusions occurred among some letter pairs such as T and 7, Z and 2, G and 6, B and 8, A and an equilateral

triangle, C and 0, and S and 5.

Using a combined criterion of both accuracy and speed, the authors recommend

that ten forms can be selected which should be highly effective; namely, C, I,

V, 0, 7, L, U, J, D and E. These should be solid forms, and finger movement

should be maximized.

44
In a second experiment, Austin and Sleight (1952b) investigated some of the

factors which might affect the speed and accuracy of tactile discriminations.

These factors included sex, handedness, learning, fingertip pressure, and

subjective confidence. The figures tested were those 25 which met the 90

percent accuracy criterion from the previous experiment.

Subjects again discriminated the shapes by touch, and also gave a rating of

their confidence in their discrimination on a five point scale. Reaction time,

confidence rating, exerted pressure, and answer were recorded for each of the

16 subjects. Eight men and eight women, half left-handed and half right-handed

were tested. Subjects made 25 discriminations in each of the 8 trials.

Accuracy Increased from 87.3 percent to 100 percent over trials, while reaction time decreased from 9.11 seconds to 3.52 seconds. Variability also

decreased over time. Mean confidence ratings increased from 3.99 to 4.92 over

trials. Pressure tended to be moderate at about 0-3 oz of pressure. Finally,

sex, handedness, and finger did not affect either accuracy or reaction time data

significantly. A short reaction time was highly correlated with high accuracy.

Confidence ratings were more highly correlated with reaction time than with

accuracy. The data indicate further that considerable learning occurred over

trials, with all persons reaching 100 percent accuracy in short periods of

training—for the 17 upper-case letters, 3 numerals and five geometric forms

tested

Craig (1979) compared confusion matrices for visually and vibrotactllely

presented letters. The tactile letters were presented in a 1.1 x 2.0 cm array

on the subject's fingertip. The correlation between visual and tactile confusion matrices was rather strong, .88, which "suggests that similar processes

are involved in identifying letters presented via the two modalities" (Craig,

1979, p. 409). These data may suggest strong similarities in processing

between visual and tactile perception. (It is not clear whether sighted or blind subjects were used—congenitally blind subjects, being much less familiar

with alphabetic characters, might not evidence the same sorts of confusions.)

Bradley (1967) investigated tactile coding of knobs using unique shapes.

While knobs are perhaps less relevant to the communication needs of the disabeled, Bradley's research provides some insight into the parameters which

determine distinctive coding shapes. Using rim surface, diameter, and thickness, as the major parameters, Bradley had subjects select one of two visual

images which matched the "felt" knob. The knobs were felt both with and without gloves in a series of experiments which studied knob parameters. In brief,

Bradley determined that 18 tactually indentifiable knobs could be constructed

by using three different rim families—smooth, fluted or knurled—which varied

in diameter by as much as 1/2 inch and in thickness by as much as 3/8 inch.

Use of gloves predictably Impaired performance on the tactual discrimination

an impairment that was not erased by training. Limiting response time to one second also degraded performance.

These data suggest that a series of discrete, different knobs could be

developed and used to code information for visually Impaired people. Such

45
a system would have to be learned, however, and does not appear to be any more

effective than the geometric forms studied by Austin and Sleight (1952). Furthermore, the alphanumeric characters the latter authors studied can be used to

form words, although it is not clear that any research has been done on the

dlscriminability of words made from tactile alphanumeric shapes. Many visually

impaired people are not necessarily familiar with the written alphabet (Aiello

and Steinfeld, 1975) so that use of tactile words may not communicate as readily and effectively as a sighted, literate person might expect.

Although the characteristics of active touch have not been studied by extensive

psychophysical research, various researchers have attempted to develop systems

for using active touch to communicate to blind observers. Thus, Nolan and

Morris (1971) suggest that tactile shapes must be a minimum of 0.2 in (0.5 cm)

for successful discrimination. Schiff (1980) suggests that there are about

5-12 discriminable shapes usable as s 3nnbols on diagrams or maps. The

following characteristics of point symbols appear to determine successful discrimination: number of points, narrow vs. wide spacing, open vs. closed, and

points vs. no points—with these features being figure rather than background.

Spacing between symbols is best if it is .09 in (2.3 mm) to 0.15 in (3.8 mm)

for discrimination of individual shapes. Although orientation is a critical

cue for vision, Schiff (1980) suggests that it is an ineffective cue for haptic perceptions. Finally, Schiff (1980, p. 144) noted that "As with most

isolated perceptual stimuli, some shapes for tactual percepton are quite

discriminable from one another in pairs or in single contexts, but may lose

their dlscriminability in other pairs or more complex contexts. It is important, therefore, to consider the context in which a tactual shape is being

presented, since depending on the context, another shape may prove better."

Schiff noted that Austin and Sleight found that only about eight letters were

fully discriminable. As noted earlier, no one appears to have investigated the

perception of words made from alphabetic shapes.

As well as point symbols, line symbols have also been investigated. Schiff

(1980) reported that the critical characteristics of line s 3rmbols are: spacing

vs. interruption, continuity vs. discontinuity, thickness, relief, smooth or rounded units vs. sharp units, and single versus double lines. Easton and

Bentzen (1980) reported that simple line configurations were generally explored

more rapidly and were more accurately represented mentally than double line

conf igrations

Shiff reported an experiment in which the characteristics of a tactile

directional indicator, designed to convey the same kind of Information as a visual arrow, were explored. In one scanning direction this indicator feels

smooth, indicating "toward", while in the other it feels sharp, indicating

"away from." Schiff commented (1980, p. 150) that "furthermore, directional

information is available throughout the entire scan along the line, but not so with the visual arrow symbol. There may be more untapped ways of presenting

information via the haptic-tactual system, providing one is not trapped by

visual conventions or visual information."

A study of 8 areal texture and 17 line symbols by James and Gill (1975)

indicated that about 10 discriminable tactile linear symbols exist, while

46
only 5 discrlminable areal symbols exist. Similarly, James and Gill (1974)

determined that variations in symbol height can provide discrlminable cues for

map symbols. Gill (1974) reported that size, elevation, form (configuration)

and orientation affect the discrimlnability of tactual symbols. He also

reported research by Nolan indicating that students made 7 percent more errors

and took 38 percent longer to read Incised figures than raised figures.

Prieser and Brecht (1981) studied the discrimlnability of tactile symbols for use in building maps for the visually handicapped. They found that subjects

could not accurately identify common building element symbols when first presented. Although the stair and carpet symbols appeared to be the most intuitively obvious, these were correctly indentified by only about one quarter of the

subjects. Nevertheless, despite the lack of initial accurate identification of

the 15 tactile symbols, these were learned in 5-6 trials, despite confusion

between some symbols. Subsequent testing of these tactile s3nnbols on a building map proved disappointing, with subjects performing at a chance level of

accuracy.

Edmondo and Macey (1968) asessed the effectiveness of tactile arrows in an overall evaluation of the lighting and directional signage systems aboard U.S.

Navy ships for use in case of fire. Sighted subjects were tested in an actual

non-toxic smoke environment in which visibility was extremely reduced. Time

to escape through a maze, and number of errors were measured. The effectiveness of a battle lantern, xenon flash lamp, retroref lective tape and tactile

arrows in guiding subjects through the maze were compared. The arrows were

cut from pavement stripping with glass beads embedded in it providing a rough

surface. The arrows were mounted six inches apart at two feet above the deck.

The results indicated that performance was worst by a factor of two for the

tactile arrows. The authors suggested that using the arrows to guide behavior

is worse than no guidance at all, because of the difficulty of discriminating

the arrows from the surrounding surface texture. Error scores were lowest for

the tactile arrows, but the time to negotiate the maze was double that for the

other signaling techniques. The authors did not assess different arrow configuration, textures, or the effects of training.

Finally, three-dimensional shapes have been investigated as coding elements.

Again, the number of distinctly discrlminable shape elements is small—between

8-10 (Schiff, 1980). Kirman (1973) suggested that the real problem in tactile

perception arises because no display "permits the perceptual organization of

linguistic units larger than the individual letter" (p. 68). Speed in visually

reading a written passage is due to the readers’ ability to organize input into

large linguistic units beyond individual letters. Coding systems for the blind

have relied upon conveying one letter at a time—a slow and inefficient way of

processing information. Kirman (1973, p. 70) concluded that "While the visual

system can integrate letter units into words and phrases by simultaneous spatial integration and while the auditory system relies solely on complex temporal

integration, tactile displays can most effectively utilize spatio temporal

Integration as well as rhythmic temporal integration." Thus, a system in which

successive stimuli can easily be Integrated into easily perceptible units must

be devised. Yet before an effective tactile display "can be properly designed,

it is necessary to determine more specifically which temporal and spatiotemporal

47
features of a tactile display most effectively meet the demands of perceptual

distinctiveness and ingratability" (Kirman, 1973, p. 72).

4.3.5 Tactile Door Marking

Both the ANSI standard and the ATBCB rule provide for tactile door indicators

to hazardous areas such as loading platforms, equipment rooms and the like.

Table 7 summarizes these provisions as well as those given in other codes. It

should be noted that both the Illinois and GSA codes suggest tactile door knob

markers for both emergency egress and hazard warnings. They do not specify

how to differentiate one cue from the other, although confusion between these

cues could lead to serious accidents. Furthermore, no researcher appears to

have directly investigated the effectiveness of tactile markings on door knobs.

Lederman and Taylor (1972) and Lederman (1974) reported various rough surfaces

that could be discriminated. Schiff (1980) reported that various areal symbols

could be discriminated by surface roughness, although he commented that the

tactile system is a bit limited on this discrimination. As a result the characteristics of textured door knobs remain unspecified. Clearly, however, the

potential for serious accidents is great if textured knobs are used to indicate

both egress and warning.

There is a great need consequently to develop unique tactile cues for both

hazard warnings on doors and for egress markings. These cues must, however,

be immediately discriminable even to severely visually handicapped people with

diabetes

48
Table 7. Tactile Warnings on Doors and Vertical Surface

ATBCB — Rule

1190.130 — Doors

ANSI A117. 1-1980

4.29 Tactile Warning

(g) Doors to hazardous areas. Provide a textured surface on any

door handle, knob, pull, or other

piece of operating hardware on doors that lead to areas that may

prove hazardous to blind people.

Such areas may include but are not

limited to, loading platforms,

mechanical equipment rooms, stages

and similar spaces. Textured surfaces may be achieved by knurling,

roughening, or applying materials

on the hand contact surface. Do

not provide textured surfaces on hardware leading to emergency

egress or on any doors other than

those leading to hazardous areas.

4.29.3* Tactile Warnings on Doors

to Hazardous Areas. Doors that lead

to areas that might prove dangerous

to a blind person (for example, doors

to loading platforms, boiler rooms,

stages, and the like) shall be made

identifiable to the touch by a textured surface on the door handle,

knob, pull, or other operating hardware. This textured surface may be

made by knurling or roughening or by

a material applied to the contact

surface. Such textured surfaces

shall not be provided for emergency

exit doors or any doors other than

those to hazardous areas.

49
Table 7 (cont.)

GSA

- provide tactile/textural cues to indicate facilitating hardware (which

allows full access by handicapped persons)

provide special door knob to hazard areas, or keep locked

Post Office

doors not intended for normal use, or which lead to hazardous area

should have textured handles or knobs

- texturing should be uniform throughout facility

DoD

provide tactile identification on doors to hazardous areas (e.g.,

loading platforms, electrical equipment rooms, machine rooms,

exposed fire escapes)

- use paint or gritted epoxy, peening, or knurled (least preferable)

HEW

use knurled door handles/knobs to indicate doors to areas that could

be dangerous

Illinois

identify emergency exit manual door openers by tactile means surface

should be roughened by knurling or applying abrasive finish —

texture should be uniform in facility

- identify doors to hazardous areas with change in texture, such as knurling or abrasive finish

- tactile warnings should be located 4 ’-6” - 5'0" from floor

New Jersey

- doors to hazardous areas (boiler rooms, stages, fire escapes, loading

platforms) shall have identifiable door handles or knobs

hardware should be non-lever type, knurled or coated with abrasive

(or have key-operated latch)

North Carolina

- doors to hazardous areas shall have knurled handles on knobs

50
Table 7 (cont.)

Texas

- doors not intended for normal use, or that might lead to hazardous

areas shall be identifiable by knurling the door handle or knob

Michigan

- use knurled door knobs, handles, push bars to indicate doors leading

to hazardous areas

Minnesota - UBC 5507

doors leading to hazardous areas must have knurled or similarly

marked door handles

Washington

- door handles or knobs on doors to stairs, loading platforms, stages,

mechanical equipment rooms, fire escapes or other hazardous areas

shall be knurled or otherwise rough.

Utah

use knurled door handles, bars on knobs with integrally stamped

knurling in hardware device to mark entrances to hazardous areas

Australia

identify danger area - perhaps by knurling

51
4.4 CONCLUSIONS

The preceding review of the research literature has suggested serious gaps in

the knowledge base underlying the code provisions for tactile communication.

For tactile warnings for horizontal surfaces, the research appears to be

limited to two major studies. Neither of these studies used a large number of

visually impaired participants nor were the characteristics of the tactile surface varied parametrically to determine the best surface. Furthermore, even

though variables such as footgear were not assessed, the limited findings disagreed about the size of the area to be identified. Clearly the determination

of the characteristics of optimal tactile horizontal cueing systems has only

begun.

There appears to be little research basis for specifying tactile warnings on doorknobs. No one has determined what physical characteristics might be

optimal for warning people of hazardous areas beyond a door. The codes mention knurled or roughened surfaces; research suggests that such characteristics are detectable, but no one has actually assessed performance with such

tactually marked knobs. Bradley’s research suggests that there are at least

three distinctive types of knob treatments which are discrimlnable . The issue

then is to extend this research to the visually impaired (including the diabetic) to determine the physical characteristics that would be optimal for tactile

communication.

With respect to informational and directional signage, the research base

suggests that the dimensions recommended by ANSI A117.1 and the ATBCB rule are more than adequate for detection of a single letter (see table 5). The only

studies investigating alphanumeric discriminability used 2 mm characters. The

code recommendations of 16 mm to 50 mm height are well beyond this. Kenshalo

(1978) suggested grooves of 1 ym are detectable; the recommended inclsed/ralsed

height of 0.8 mm is above this. The issue of spatial separation between characters, however, is not addressed by the codes. Heinrichs and Moorehouse (1969)

recommend no less than 3.0 mm if diabetic blind observers are considered.

Whether these proportions are optimum for detection is not clear from the

limited research reviewed. Aiello and Steinfeld (1979) report that subjects

found stroke widths of 1/16 in to be too wide, for example.

Other issues such as the familiarity of visually handicapped people with

printed (taccile) alphanumeric characters and optimum placement of tactile

signs are also not addressed. In the existing codes use of symbolic presentation of spatial information and non-visual landmarks to guide the visually

handicapped are not included, either. Consistent placement of tactile signs

so that they can be readily found is as critical as the information on the

sign (Leonard and Newman, 1970).

The final issue is that of tactile guidance for egress. The codes related to

accessibility do not specify that exit routes be marked in any fashion tactile

or otherwise. Yet NFPA 101 specifies clearly that exits be marked visually—

cue unavailable to visually handiapped users. There is, consequently, a great

need to develop tactile exit signs and exit route markers to guide visually

52
handicapped users through a building during emergencies (and normal conditions).

As noted earlier, such cueing could serve the needs of those who are temporarily

blinded due to smoke and fire. These cues must not be confused with those for

hazard warnings, however.

4.5 TACTILE RESEARCH NEEDS

Although both types of tactile communication—directional information and hazard

warning—require further research, the communication of hazard warning and

emergency egress appears most critical due to the greater threat to life safety.

The design of hazard warnings must be differentiated from that for emergency

egress markings, to avoid confusions to the user - who urgently requires both

kinds of information.

Future research should involve the parametric assessment of hazard warnings

and egress indicators to be placed on horizontal surfaces and detected by foot

or cane. It should expand the work done by Templer and Aiello and Steinfeld

to include a directional egress marker such as that suggested by Schiff (1980).

Handicapped users including the visually and mobility impaired should be used

along with a control group of blindfolded nondisabled users. The latter group

should be included to assess performance under temporarily disabling conditions.

Characteristics of footgear and cane use must be assessed as well as those of

the pavement/surface markers. The latter parameters include the area of the

marked surface, distance from hazard, placement of egress markers, height

(raise) of the marker, texture, pattern, resiliance, slip resistance, and

contrast with surrounding materials. Behavioral characteristics such as gait,

pace, stopping distance and cane use should be measured, along with the rated

difficulty of detecting the marker. Personal observations and preferences

should also be included. Consistent measures of the degree and kind of visual

handicap must be obtained, along with demographic measures such as age, sex,

education, movement experience and duration of handicap. For egress markers,

the problem is to assess the characteristics of a series of tactile markers

for their detectability and effectiveness in guiding behavior.

Once the design of the most effective cues for hazard warnings and egress

markers on horizontal surfaces has been determined, the same problem must be

researched for vertical surfaces such as doors. A set of immediately discriminable cues for warning and for egress must be developed and assessed for

visually handicapped and other users. Furthermore, the design of more effective tactile signage. Including specialized shapes, should be researched for

visually handicapped users.

Experimental determination of the characteristics of effective tactile surface

cues for both hazard warning and emergency egress guidance is essential. Such

research is needed for providing the technical basis needed for decisions

about code provisions to increase the accessibility of the built environment.

53
5 . CONCLUSIONS

In the previous sections the communication code requirements for each of three

sensory modalities have been presented. The research base supporting each

provision has been discussed, and recommendations for further research proposed .

A review of the preceding sections indicates that the research base underlying

many of the provisions is inadequate. In many cases, the effectiveness of

the proposed systems has not been sufficiently determined for either disabled

or non-disabled users. This is particularly true in the tactile area, where

not only is the research base insufficient, but the code provisions also overlook the critical issue of alerting for emergency egress.

Based upon the proceeding review of the research literature, several problem

areas can be viewed as high priority for further research. These are summarized

in table 8. Although communication systems are intended for both normal and

emergency alerting, further assessment of emergency and hazard warning indicators is considered to be of highest priority. As a result, the quantification

of the most effective design characteristics of tactile hazard warnings and

emergency egress markers is one of the most Important aspects of improving

communication systems for disabled building users. As noted earlier, determination of more effective egress indicators can also aid all building users during emergency conditions when visibility is impaired. A second high priority

area is the assessment of more effective visual alarms including further exam- ination of flash rate, temporal patterning and general conspicuity of exit

signs and emergency indicators. A third, related area is the determinnation of

the characteristics of audible alarms for which temporal patterning, frequency,

and intensity must be considered for disabled users.

Other communication areas requiring further research are related to the general

accessibility and use of buildings. Direction finding within buildings can pose

a significant problem for the visually impaired. The characteristics of visual

and tactile signage require further delineation to determine their optimal

characteristics. Use of tactile graphic symbols requires further exploration

as a consideration for those who are not fluent in braille or alphanumeric

characters, for example. Finally considerable research is needed on the

design for improved speech Intelligibility systems in buildings, which could

form the basis of design recommendations for improving the acoustic characteristics of the built environment.

54
Table 8. Recommended High Priority Areas for Research on Building Communication Systems for Disabled Users

1. Quantify characteristics of optimal tactile hazard warning markings for

horizontal surfaces, walkways and doors. Determine properties of effective tactile markings for egress, and directional indicators for use during building emergencies.

2. Quantify conspicuity characteristics of more effective visual and acoustic

alerting systems, including pulsed exit directional indicators and audible

alarms

3. Determine characteristics of combined tactile and visual markers for

direction finding and information. Assess properties of s3nnbolic and

alphanumeric characters as well as combinations of both.

4. Provide design recommendations for improved systems speech intelligibility,

alarms, and acoustic transmission in public assembly areas.

55
6.1 CODE REFERENCES

General

American National Standard, A 117.1-1980, Specifications of Making Buildings

and Facilities Accessible to and Usable by Physically Handicapped People. New

York: American National Standards Institute, 1980.

Architectural and Transportation Barriers Compliance Board. Minimum Guidelines

and Requirements for Accessible Design. 36 CFR Part 1190. Federal Register,

1981, 46, 4270-4304.

Federal Agency Documents

U.S. Department of the Army, Office of the Chief of Engineers, Design for the

Physically Handicapped , Manual No. 1110-103, Washington, D.C.: Government

Printing Office, October 15, 1976.

U.S. General Services Administration, Public Building Service, Design Criteria:

New Public Building Accessibility , Washington, D.C.: Government Printing

Office, December 1977.

U.S. Department of Health, Education, and Welfare, Office of Facilities

Engineering, Technical Handbook for Facilities Engineering and Construction

Manual: Part 4 - Facilities Design and Construction , Washington, D.C.:

Government Printing Office, August 1978.

U.S. Postal Service Real Estate and Buildings Department, United States Postal

Service Standards for Facility Accessibility for the Physically Handicapped , Washington, DC.: Government Printing Office, June 27, 1979.

State Documents

Commonwealth of Massachusetts, Department of Public Safety, Rules and

Regulations

State of Illinois Capital Development Board, Accessibility Standards

Illustrated , by M. A. Jones, Springfield, Illinois: The Capital Development

Board, June 1978.

The University of Michigan, The Office of Disabled Student Services, Barrier

Free Design: A Design Manual Code , by G. Selim, Ann Arbor: The University

of Michigan, 1977.

Kiewel, H. , and Salmen, J. , Access ible Architecture: An Illustrated Handbook

Based on Minnesota State Building Code, 1977.

State of New Hampshire, Governor's Commission for the Handicapped, The

Architectural Barrier Free Design Code for the State of New Hampshire, 1978.

56
State of New Jersey, Department of the Treasury, Division of Building and

Construction, Barrier-Free Design Regulations (for Providing Facilities for the

Physically Handicapped in Public Buildings) , 1977.

State of North Carolina, Governor's Study Committee on Architectural Barriers

and the North Carolina Department of Insurance, An Illustrated Handbook of the

Handicapped Section of the North Carolina State Building Code, by R. I. Mace,

1974.

State of North Carolina, North Carolina Special Office for the Handicapped,

Department of Insurance, Accessibility Modifications; Guidelines for Modifications to Existing Buildings for Accessibility to the Handicapped , by

R. I. Mace, Barrier Free Environments, 1976.

Ohio Governor's Committee on Employment of the Handicapped, and Schooley

Cornelius Associates, Access for All; An Illustrated Handbook of Barrier Free

Design for Ohio , 1977.

The University of Texas System, Office of Facilities Planning and Construction,

Senate Bill No. Ill - Guidelines , by E. E. Farrera, September 1973.

Utah State Building Board, Planning and Design Criteria to Prevent Architectural Barriers for the Aged and Physically Handicapped , by E. H. Johnson,

Fourth Edition, 1978.

Small, Robert, and Allan, Barbara, An Illustrated Handbook for Barrier Free

Design: Washington State Rules and Regulations, 1976.

Foreign Documents

Standards Association of Australia, Australian Standard 1428-1977: Design

Rules for Access by the Disabled , North Sydney: Standards Association of

Australia, 1977.

6.2 VISUAL COMMUNICATION REFERENCES

1. U.S. Bureau of the Census. Statistical Abstract of the United States

(100th edition). Washington, D.C.: U.S. Government Printing Office,

1979.

2. Murphy, J. How Does a Blind Person Get Around ? New York: American

Foundation for the Blind, Inc., 1975.

3. American Foundation for the Blind. Facts About Blindness. New York:

Author, 1975.

4. Bartley, S. H. A Clarification of Some of the Procedures and Concepts

Involved in Dealing with the Optic Pathway. In R. Jung and H. Kornhuber

(eds.). The Visual System: Neurophysiology and Psychophysics . Berlin:

Sprlnger-Verlag , 1961.

57
5o Gerathewohl, S. J» Conspicuity of Steady and Flashing Light Signals:

Variation of Contrast. J. Opt. Soc . Amer. , 43 (7), 567 (1953).

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Variation Among Frequency, Duration and Contrast of Signals. J . Opt

Soc. Amer. , 47 , (1), 27 (1957).

7. Crawford, A. The Perception of Light Signals: The Effect of the Number

of Irrelevant Lights. Ergonomics , ^ (3), 47 (1962).

8. Crawford, A. The Perception of Light Signals: The Effect of Mixing

Flashing and Steady Irrelevant Lights. Ergonomics , ^ (3), 287 (1963).

9. Wiley, A. E. High-rise Building Fire. Fire Journal , 66 , 6 (1972).

10. Bryan, J. L. A Study of the Survivors Reports on the Panic in the Fire

at the Arundel Park Hall in Brooklyn, Maryland on January 29, 1956 . Unpublished report. College Park, Maryland: University of Maryland,

1956.

11. Howett, G. L., with Kelly, K. L., and Pierce, E. T. Emergency Vehicle

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Office, September 1978.

12. Jeavons , P. and Harding, G. F. A. Photosensitive Epilepsy; Clinics

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13. Holmes, J. G. The Language of Flashing Lights. In The Perception and

Application of Flashing Lights. Toronto; University of Toronto Press,

1971.

14. Meister, D. and Sullivan, D. J. Guide to Human Engineering Design for

Visual Displays . Report prepared under Contract No. N00014-68-C-0278

for the Office of Naval Research, August 1969.

15. Heglin, H. J. NAVSHIPS Display Illumination Design Guide; Section II,

Human Factors . Technical document 223. San Diego, California: Naval

Electronics Laboratory Center, July 1973.

16. Tinker, M. A. Legibility of Print. Ames, Iowa: University of Iowa

Press, 1963.

17. Bishop, H. P. and Crook, M. H. Absolute Identification of Color for

Targets Presented Against White and Colored Backgrounds . (WADD Technical

Report 60-611). Wright Air Development Division, Wright-Patterson AFB,

Ohio, March 1961.

58
18. Hilgendorf, A. L. and Milenski, J. Effects of Color and Brightness

Contrast on Target Acquisition . SEEKVAL Project lAl. (AMRL-TR-74-55)

Aerospace Medical Research Laboratory, Wright-Patterson AFB, Ohio, July

1974.

19. Wagner, D. W. Target Acquisition with Color vs. Black and White

Television. (NWC TP 5000). Naval Weapons Center, China Lake, Calif.,

October 1975.

20. Roth, E. M. and Finkelstein, S. Light Environment: In Compendium of

Human Responses to the Aerospace Environment (E. M. Roth, ed.). NASA

Contractor Report NASA CR-1205-1, Washington, D.C., November 1968.

21. McLean, M. V. Brightness Contrast, Color Contrast and Legibility.

Human Factors , l_y 521 (1965).

22. Illuminating Engineering Society of North America. lES Lighting

Handbook (Reference volume). New York: Author, 1981.

23. Sorensen, R. J. Design for Accessibility . New York: McGraw-Hill, 1979.

6.3 ACOUSTIC COMMUNICATION REFERENCES

24. Anon., A proposed standard fire alarm signal. Fire Journal, July, 1975.

25. Anon., Hearing aids and audiometers. Medical Research Council, Special

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calibration of pure-tone audiometers. International Organization for

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27. Anon., Life Safety Code, No. 101, 6-3141, National Fire Prevention

Association, Boston, 1973.

28. Anon., National Fire Codes, Vol. 7, 6-3.1, National Fire Protection

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29. Anon., Uniform Building Code, Standard No. 43-6,

30. Beasley, W. C., Characteristics and distribution of impaired hearing in

the population of the United States, J. Acoust. Soc . Am., 12 , 114-121,

1940.

31. Beck, L. B., ed . , Handbook of Hearing Aid Measurement 1980, Veterans

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32. Butler, H., Sounding Off, Building Services, April, 1980.

33. Corliss, E., Personal communication, 1981.

59
34. Corso, J. F., Presbycusis as a complicating factor in evaluating noiseinduced liearing loss, in Effects of Noise on Hearing, Henderson et al .

eds.. Raven Press, N.Y., 1976.

35. Davis, D., Uses, abuses, and misuses of the critical distance

concept, Syn-Aud-Con-Tech Topic, 7^(12), 1-8, 1980.

36. Davis, D., and Davis, C., Sound System Engineering, Howard W. Sams and

Company, Inc. /The Bobbs-Merill Co., Inc., Indianapolis, Indianapolis,

1976.

37. Davis, H., et. al., (1947), Hearing Aids: An Experimental Study of

Design Objectives, Harvard University Press, Cambridge, 1947.

38. Davis, J., (1974), Performance of young hearing-impaired children on a test of basic concepts, J. Speech Hear, Res., 17 , 342-351, 1974.

39. Duequesnoy, A. J., and Plomp, R., Effect of reverberation and noise on

the intelligibility of sentences in the case of presbyacusis, J. Acoust.

Soc . Am., 68(2) , 537-544, 1980.

40. Egan, M. D., (1978), Concepts in Building Fire Safety, John Willey and

sons. New York, 1978.

41. Finitzo-Heiber , T., and Tillman, T. W., (1978), Room acoustics effects

on monosyllabic word discrimination ability for normal and hearingimpaired children, J. Speech Hear. Res., 440-458, 1978.

42. Green, D. M., et al . , (1975), A proposed standard fire-alarm signal.

Committee on Hearing and Bioacoustics and Biomechanics, J. Acous. Soc.

Am., ^(3), 756-757, 1975.

43. Houtgast, T., Indoor speech intelligibility and indoor noise level

criteria, in Proceedings of the Third International Congress on Noise as

a Public Health Problem, ASHA Report 10, The American Speech-LanguageHearing Assoc., 1980.

44. Houtgast, T., and Steeneken, H. J. M., The modulation transfer function

in room acoustics as a prediction of speech Intelligibility, Acustica,

2^, 66-73, 1973.

45. Houtgast, T., Steeneken, H. J. M., and Plomp, R. , Predicting speech

intelligibility in rooms from the modulation transfer function. I.

General room acoustics, Acustica, 60-72, 1980.

46. Jensen, R., ed.. Fire Protection for the Design Professional, Calmers

Books, 1975.

47. Klein, W., Articulation loss of consonants as a basis for the design

judgment of sound reinforcement systems, J. Audio Eng. Soc., 19(11),

920-922, 1971.

60
48. Kurtovic, H. , The Influence of reflected sound upon speech

Intelligibility, Acustica, 2^, 32-39, 1975.

49. Laney, M. D., The prevelence of communication disorders: A review of

the literature. Am. Speech-Language-Hearing Assoc., Rockville, Maryland,

1980.

50. Lattam, H. G., The signal-to-noise ratio for speech intelligibility —

an auditorium acoustics design index. Applied Acoust. 12(4) , 252-320,

1979.

51. Lawrence, A. B., Architectural Acoustics, Applied Science Publishers,

Ltd., London, 1980.

52. Martin, M. C., Communication systems for deaf people: A review of

possibilities, J. Med. Eng. Technol . , January, 16-19, 1977.

53. Maxfield, J. P. and Albersheim, W. J., An acoustic constant of

enclosed spaces correlatable with their apparent liveness, J. Acoust.

Soc. Am., j^(l), 71-79, 1947.

54. Nabelek, A. K. and Pickett, J. M., Reception of consonants in

a classroom as affected by monaural and binaural listening, noise,

reverberation and hearing aids, J. Acoust. Soc. Am., 56(2), 628-639,

1974.

55. Nabelek, A. K. and Pickett, J. M. , Monaural and binaural speech perception through hearing aids under noise and reverberation with normal and

hearing-impaired listeners, J. Speech Hear. Res., 17, 724-739, 1974.

56. Northicott, W., The hearing impaired child in a regular classroom. The

Alexander Graham Bell Association, Washington, D.C., 1973.

57. Peutz, V. M. A., Articulation loss of consonants as a criterion for

speech transmission in a room, J. Audio Eng. Soc., 19(11) , 915-919,

1971.

58. Peutz, V. M. A., Speech reception and information, Syn-Aud-Con-Tech

Topic, _5(12), 1-5, 1978.

59. Plomp, R., Auditory handicap of hearing impairment and the limited

benefit of hearing aids, J. Acoust. Soc. Am., 63(2 ) , 533-549, 1978.

60. Plomp, R. , Binaural and monaural speech intelligibility of connected

discourse in reverberation as a function of azimuth of a single competing

sound source (speech or noise), Acustica, 200-211, 1976.

60. Plomp, R. and Duquesnoy, A. J., Room acoustics for the aged, Acustica,

in press.

61
51^ Plorap, R. and Mimpen, A, M» , Improving the reliability of testing the

speech reception threshold for sentences. Audiology, 18, 43-52, 1979.

62, Plomp, R. and Mimpen, A. M., Speech-reception threshold for sentences as

a function of age and noise level, J. Acoust. Soc. Am., 66(5), 1333-1342;,

1979.

63, Plomp, R., Steeneken, H. J. M., and Houtgast, T., Predicting speech

intelligibility in rooms from the modulation transfer function. II.

Mirror image computer model applied to rectangular room, Acustica, 46 , 73-81, 1980.

64, Puzyna, C., Investigation of the barrier perception mechanisms of the

blind. Archives of Acoustics (Warsaw), ^(2), 89-107, 1979.

65, Richardson, E. G. and Meyer, E., Technical aspects of sound, Vol. Ill,

Recent Developments in Acoustics, Elsevier Publishing Company, New York,

1962.

66, Steel, L., Inventory of communication barriers, 1980.

67, Steeneken, H. J. M., and Houtgast, T., A physical method for measuring

speech-transmission quality, J. Acoust. Soc. A., 67(1), 318-326, 1980.

,4 TACTILE COMMUNICATION REFERENCES

68.

Austin, T. R. and Sleight, R. B., Accuracy of Tactual Discrimination of

Letters, Numerals, and Geometric Forms. Journal of Experimental Psychology, 1952, 43, 239-247.

59, Austin, T. R. and Sleight, R. B., Factors Related to Speed and Accuracy

of Tactual Discrimination, Journal of Experimental Psychology, 1952,

44, 283-287.

70, Bradley, J. V., Tactual Coding of Cylindrical Knobs. Human Factors,

1967, 9, 483-496.

71, Craig, J. C., A Confusion Matrix for Tactually Presented Letters.

Perception and Psychophysics , 1979, 26, 409-411.

72, Easton, R. D. and Bentzen, B. L., Perception of Tactile Route

Configuration uration by Blind and Sighted Absences. Visual Impairment

and Blindness , 1980, 74, 254-265.

73, Geldard, F. A., Pattern Perception by the Skin. In D. R. Kenshalo

(ed.). The Skin Senses. Springfield, 211; Charles C. Thomas, 1968,

pp. 304-321.

74, Geldard, A. The Human Senses (2nd ed . ) . New York: Wiley, 1972.

62
75. Genensky, S. M. Architectural Barriers to the Partially Sighted and

Solutions. Architectural Record, 1980, May, pp. 65 & 67.

76. Gill, J. M. Tactual Mapping, American Foundation for the Blind, Research

Bulletin , 28, 1974, 57-80.

77. Hahn, J. F., Tactile Adaptation. In D. R. Kenshalo (ed.). The Skin

Senses . Springfield, IL: Charles C. Thomas, 1968, pp. 195-222.

78. Heinrichs, R. W. and Moorhouse, J. A., Touch-perception Thresholds In

Blind Diabetic Subjects In Relation to the Reading of Braille Type. The

New England Journal of Medicine , 1969, 280, pp. 72-75.

79. Heller, M. A. Reproduction of Tactually Perceived Forms. Perceptual and

Motor Skills , 1980, 50, 943-946.

80. James, G. A. and Gill, J. M., Mobility Maps for the Visually Handicapped:

A Study of Learning and Retention of Raised Symbols. American Foundation

for the Blind; Research Bulletin , 1974, 27, 87-98.

81. James, G. A. and Gill, J. M., A Pilot Study on the Dlscrlmlnablllty of

Tactile Areal and Line Symbols for the Blind. American Foundation for

the Blind; Research Bulletin , 1975, 29, 23-31.

82. Kenshalo, D. R. , Biophysics and Psychophysics of Feeling. In Carterette,

E. C. and Friedman, M. P. (Eds.). Handbook of Perception , Vol. VIB.

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84. Lappln, J. S. and Foulke, B. Expanding the Tactual Field of View.

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85. Lassen, P. and Berry, J. Signing for the Handicapped. Signs of the

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86. Lawrence, D. M. , Cobb, N. J., Beard, J. I. Influence of Active Encoding

for Common Objects. Perceptual and Motor Skills . 1978, 47, 596-598.

87. Lederman, S. J. Tactile Roughness of Grooved Surfaces: The Touching

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88. Lederman, S. J. and Taylor, M. M. Fingertip Force, Surface Geometry, and

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63
39

Lindblom, U= and Lindstrom, Tactile Thresholds of Normal and Blind

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64
NBS»n4A tREv. 2-ec) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 81-2428

2. Performing Organ. Report No.l 3. Publication Date

4. TITLE AND SUBTITLE

Coimrami cation Requirements for Disabled Users of Buildings

5. AUTHOR(S)

Belinda L. Collins, William F. Danner, Robert L. Tibbott

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

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8. Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. Stote, ZIP)

Architectural and Transportation

Barriers Compliance Board

330 C Street, S.W.

Washington, D.C. 20202

10. SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) Communication systems in buildings are designed to provide both emergency and

directional information to all building users. Yet such systems, which are typically comprised of visual signs and audible alarms, may fail to reach some of the estimated twenty-seven million hearing or vision impaired people in the

United States. As a result, a number of alternative communication systems have

been proposed for inclusion in accessibility guidelines. In the following pages

the research base underlying commimication provisions for each of three sensory

modalities, vision, hearing and touch, are reviewed. In addition, various proposed code recommendations are presented and discussed. The adequacy of the

research base for each provision is discussed along with the need for various

code provisions. It is noted that code provisions for tactile warnings and

exit markings are particularly inadequate. Recommendations for further research

into tactile warnings , tactile signage , and visual alarms are suggested.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Accessibility; alarms; blind; communication; code requirements; deaf; directional

indicators; handicapped users; tactile warnings.

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