Naval Submarine Medical Research Laboratory

NSMRL REPORT 1208 7 OCTOBER 1997

Effects of low-frequency water-borne sound on divers:

Open water trial

C. C. Steevens, MD

R. Sylvester

J. Clark

Released by

M. T. Wooster, CAPT, MSC, USN

Commanding Officer

Naval Submarine Medical Research Laboratory

19971121 017

)HC QUALITY I275ZCÜESD ,

Approved for public release; distribution unlimited
Effects of low-frequency water-borne sound on divers:

Open water trial

C. C. Steevens and R. Sylvester

Naval Submarine Medical Research Laboratory

J. Clark

Naval Aerospace Medical Research Laboratory

Naval Submarine Medical Research Laboratory

Report 1208

Space and Naval Systems Warfare Command Task

Naval Medical Research and Development Command

Research Work nit 63747N-5503

Approved and Released by

M. T. Wooster

Commanding Officer

NavSubMedRschLab

LX>TIC QUALITY XI?C?SÜT!D 3

Approved for public release; distribution unlimited
Summary Page

The Problem:

Divers may be exposed to intense underwater sound. Previous research in this area has been conducted in enclosed environments only, characterized by standing wave acoustics. The effects on

divers of low-frequency water-borne sound in the open water remains unknown.

The Findings:

There is no indication that low-frequency water-borne sound exposures in the open water present

any additional risk compared to similar exposures in enclosed environments.

The Application:

The results of this study have been used in establishing recommendations for safe exposure of divers to low-frequency sonar transmissions.

Administrative Information

This research was carried out under a Space and Naval Systems Warfare Command Task,

63747N-5503, Low Frequency Active Sonar, and the Naval Medical Research and Development

Command. The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of the Navy, the Department of Defense, or the US Government. It was approved for publication on 7 Oct 97 and designated as NSMRL Report 1208.

li
Abstract

Navy divers may be exposed to active sonar transmissions while underwater. Previous manned

experiments to determine safe levels of exposure have all been conducted in enclosed settings

characterized by standing wave sound fields. The purpose of this experiment was to determine if

plane wave (open water) acoustics alters the physiological or subjective responses of exposed divers compared to standing wave exposures. 54 manned exposures to two low-frequency underwater acoustic signals were performed at depths of 30 and 60 feet in a fresh water spring. Two

projectors were used to create a plane progressive traveling acoustic wave. Divers were exposed

in both helmeted and unhelmeted diving rigs. Effects on hearing, vestibular function, cardiac

rhythm, and a key-insertion task were measured. Subjective responses were also recorded. In addition, the effects of neoprene wet suits on sound attenuation were measured. Slight decrements

in hearing acuity were detected, but these results were confounded by circumstances unrelated to

the underwater sound exposures, such as ear squeezes from diving, and microphone feedback

noise. No adverse effects in vestibular function, cardiac rhythm, or key insertion performance

were detected. Subjective responses revealed that divers were moderately annoyed by the underwater sound, but overall found the exposures tolerable. Neoprene wet suits generally act to attenuate low-frequency sound exposures, but under certain circumstances may also accentuate a

sound exposure, possibly through a resonance effect. There is no indication from the results of

this study that low-frequency water-borne sound exposures in the open water present any additional risk to divers compared to similar exposures in enclosed environments.

in
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IV
Effects of low-frequency water-borne sound on divers:

Open water trial

Navy divers may be exposed to active sonar transmissions while underwater. Anecdotal reports from divers have indicated that

such transmissions can be felt as well as

heard. One such report from a diver exposed

to low-frequency water-borne sonar consisted

of a sensation of numbness for two hours following the exposure, thus raising concerns regarding the potential health risks to divers

who may be in the area of these transmissions

(P.F. Smith, Personal Communication, "Interview with a Diver Exposed to Intense LowFrequency Water-Borne Sound," 25 Feb

1993). Consequently, recent efforts have

been focused on defining in greater detail the

effects on divers of underwater sound, particularly low-frequency transmissions in the frequency range of 160 to 320 Hz, and in the

process determining levels of safe exposure.1

The current experiment is the final phase

of a two year study addressing the effects of

low-frequency water-borne sound on divers.

The study progress to this point may be summarized as follows:

Thermal Effects:

Mathematical modeling concluded that the

temperature increase produced by exposure to

underwater sound at a frequency less than

1000 Hz, and a sound pressure level less than

160 dB will produce a temperature rise of less

than 1 °C, and therefore not result in a significant thermal effect on human tissue (Nyborg,

1993).

Bubble Growth:

Further mathematical modeling concluded

that underwater sound exposure at all low frequencies (any frequency less than an order of

hundreds of kilohertz) and sound pressure levels in excess of 210 dB can be expected to result in significant micro-bubble growth

(bubbles with initial radii from 1-10 mm) by

the process of rectified diffusion, and therefore divers exposed to these conditions may

be at increased risk of such effects as decompression sickness (Crum and Mao, 1994). For

sound pressure levels below about 190 dB,

however, significant bubble growth is unlikely.

Lung Response:

Modeling of wave propagation within the

airways resulting from sound pressure applied

at the chest wall concluded that there can be

considerable amplification of pressure within

the airways in response to frequencies surrounding 250 Hz (Suki, Habib, & Jackson,

1994). Due to limitations of the model, however, the magnitude of the pressure amplification, and the level of exposure for which

barotrauma might be expected could not be determined.

Lung vibration studies (n = 5 subjects) using an experimental non-invasive vibration

amplitude measurement system (NIVAMS)

showed a lung resonance for humans between

100 and 200 Hz at the surface which was reduced in amplitude with subjects at a depth of

10 feet (Rogers, Grille, & Lewis, 1994). Determining lung resonance in divers is impor1 NOTE: All notations regarding underwater sound levels are specified in decibels (dB) referenced to 1 ,aPa

unless otherwise noted.
tant for establishing thresholds of injury, because for a given level of low frequency excitation, the vibration of the lungs (and hence

the risk of damage) will be highest at resonance. Exposures during these studies consisted of approximately 30,4-6 second pulses

using frequencies between 50 and 500 Hz at

levels of approximately 130 dB.

Experiments on three pigs at depths of 6-

10 feet exposed to underwater sound for up to

35 minutes total exposure time (using 5-minute intervals of continuous exposure) at frequencies between 100 and 400 Hz and

intensity levels ranging from 161 to 177 dB

showed no detectable damage to lungs or abdominal viscera as a result of the sound exposure (Lehner, 1994). However, due to initial

problems with anesthesia in the totally submerged pig, results from 10 additional sound

exposed pigs were inconclusive.

Tactile Perception:

Experiments at NSMRL (n = 4 divers) and

Syracuse University (n = 3 subjects) showed

that vibrotactile sensitivity is not significantly

affected by ambient pressure and water immersion, suggesting that vibrations resulting from

underwater sound present no additional risk,

compared to similar vibrations in air, with regards to the cutaneous sensory system (Verrillo, Bolanowski, Baran, & Smith, 1994).

Further, mathematical calculations concluded

that for underwater sound at 250 Hz, the

sound intensity required to induce mild discomfort through the cutaneous sensory system

would need to be at least three orders of magnitude greater than the auditory pain threshold

as determined in air (an equivalent of approximately 220 dB underwater) (Bolanowski,

1994).

Auditory Effects:

Hearing experiments conducted at

Roosevelt Roads, Puerto Rico with bareheaded SCUBA divers at 30 FSW showed

that four-minute exposures to continuous warble tones (+/- 5% of center frequency) with

center frequencies of 125 Hz (n = 9 divers)

and 250 Hz (n = 10 divers) produced no temporary threshold shifts in hearing greater than

15 dB for exposure levels up to 161 dB

(Smith, Sylvester, Baran, & Steevens, 1994).

It was concluded that such exposures do not

present a significant risk to diver hearing.

During these same studies, divers did report

various symptoms including joint pains, dizziness, alterations in visual fields, and headaches, but these symptoms were only in

response to higher frequency transmissions

(500-4000 Hz). Intensities for the higher frequency exposures extended up to 196 dB.

Vital Organ Function:

Experiments conducted at SUBASE

NLON found that divers (n = 22) whose torsos were intermittently exposed to 250 Hz (+/-

12.5 Hz) warble tone signals for a total of 15

minutes at levels up to 160 dB experienced no

significant measurable effects on performance

or vital organ function (Steevens, Schlichting,

et al., 1994).

Experiments conducted at the Naval Experimental Diving Unit (NEDU) (n = 18 divers, 33 dives) using intermittent 5-minute

exposures for a total of 15 minutes at 33 FSW

(simulated depth in a hyperbaric wet pot facility) to 240 Hz (+/- 80 Hz) warble tone signals

at levels up to 160 dB also revealed no measurable effects on vital organs (Steevens,

Knafelc, et al., 1994).

A second set of experiments conducted at

NEDU (n = 22,156 dives), with exposure to

three different representative low-frequency

water-borne sound waveforms (a 240 +/- 80

Hz warble tone signal, a pure tone sweep signal from 160 to 260 Hz, and a pure tone

sweep signal from 230 to 320 Hz) using 100

second exposures with a 50% duty cycle for a

cumulative exposure of 15 minutes per dive,
at various depths and using various rigs resulted in no events compromising the divers

(Russell and Knafelc, 1995). In these experiments, a "compromised event" was defined as

one in which a diver could become a casualty

or burden to others in an operational setting as

a result of the sound exposure. Tests of vestibular function were also performed during

this study, and although minor changes were

seen, the clinical significance of such changes

remains uncertain.

Subjective Responses:

Results of the tests referred to above at

Roosevelt Roads (n = 19), SUBASE (n = 22),

and NEDU (n = 30) showed that most subjects felt vibrations at 130 dB and higher, described such sensations as mildly to

moderately annoying but tolerable, and suffered no lasting aftereffects of those exposures. The frequencies covered in these

experiments consisted of 3 separate warble

tone signals, and 2 pure tone sweep signals

ranging from 100 to 320 Hz (see above).

Reports from three subjects, however, remain topics of concern. One subject reported

numbness for 2 hours after an unknown exposure in the open sea (P.F. Smith, Personal

Communication, "Interview with a Diver Exposed to Intense Low-Frequency Water-Borne

Sound," 25 Feb 1993). The sensations disappeared, with no apparent after-effects. One report of knee pain was received from a subject

whose knees were exposed to a warble tone

signal (250 +/-12.5 Hz) at 160 dB intermittently for about 15 minutes (Steevens,

Schlichting, et al., 1994). The knee pain resolved completely within 18-24 hours after

the sound exposure ended. This subject had

prior knee surgery with retained hardware in

the affected knee, raising the issue of possible

predisposing factors increasing one's susceptibility for adverse effects of water-borne

sound. During tests at NEDU, one subject at

60 FSW using a US Navy MK-20 underwater

breathing apparatus (full face mask, no helmet, with surface supplied air) reported lightheadedness, dizziness, not feeling awake and

alert, and being unable to concentrate after

about 12 minutes into a planned 15 minute

continuous exposure to a warble tone signal

(240 Hz +/- 80 Hz) at 160 dB (Steevens,

Russell, et al., 1994). The subject maintained

a level of consciousness which allowed him to

remove himself from the water safely without

assistance. The acute symptoms initially resolved after approximately 26 minutes postdive, but the subject experienced two similar

recurrences within a 36 hour period following

the sound exposure. Medical evaluation of

this subject was inconclusive, and his symptoms appeared to have resolved without any

measurable persistent deficits. However, during an interview approximately one year after

the exposure, the subject reported persistent

impairment which he subjectively attributed

to the sound exposure; specifically, a decrease

in hand steadiness, increased irritability, insomnia, and impaired memory function. He

declined any further neuropsychological

evaluation at that time. Nineteen months after

the exposure, he developed symptoms consistent with a seizure disorder. Further workup

was again non-diagnostic, but he is currently

receiving anti-seizure and antidepressant therapy. This subject had received a longer duration of continuous exposure within the

160-320 Hz frequency range than any other

experimental subject.

Table I summarizes the above results.

The manned exposures described above

were all conducted in enclosed settings where

the sound field was characterized by a standing wave field that varied in a deterministic

manner in response to the changing signal

characteristics. Although the sound pressure

levels in these experiments were controlled to

reflect potential open water (occupational)

exposures, the phase relationship between
Table 1

Studies ofLow Frequency Underwater Sound

Time of Adverse

Author Method

Modeling

Frequencies

<1000 Hz

Max SPL

< 160 dB

Exposure

Minutes

Effects

Nyborg None

Crum and Mao Modeling <1000 Hz <190 dB Minutes None

Suki et al. Modeling 250 Hz not specified Minutes Elevation of

intra-airway

pressure

Rogers et al. Human exp. (n=5) 50-500 Hz 130 dB 4-6 sec x 30 None

Lehner et al. Pig exp. 6-10

(FSW (n-3)

100-400 Hz 161-177 dB 5 min. x 7 None

Verrillo et al. Human exp.

(n=6) + Modeling

250 Hz <180 dB Minutes None

Smith et al. Human exp. (n=9) 125 Hz

(warble +1-5%)

161 dB 4 minutes None

Smith et al. Human exp.

(n=10)

250 Hz

(warble +1-5%)

161 dB 4 minutes None

Steevens.et al. Human exp head

out (n = 22)

250 Hz

(warble +1-5%)

160 dB 5-10 min.

(cont.) + 30-

60 sec. x 5

Knee pain in

subject

Steevens et al. Human exp. 33

FSW (n = 18)

240 Hz (warble +/-33%)

160 dB 5 minutes None

Steevens et al. Human exp. 60

FSW (n = 1)

240 Hz

(warble +/-

33%)

160 dB 15 minutes somnolent,

light-headed,

dizzy,

unable to

concentrate

Russell et al. Human exp. 160-320 Hz 160 dB 100 sec. x 9 None

33,60,66,99,130 (3 varying

FSW (n = 24) signals)

pressure and acoustic particle velocity was different from that expected in an open water setting. That is, in the open water one would

expect a plane progressive traveling acoustic

wave where pressure and particle velocity are

in phase, as opposed to the out of phase relationship seen in the enclosed laboratory facilities. While it has been hypothesized that

pressure, not particle velocity, is the fundamental variable likely to cause physiological

responses from underwater sound exposures,

and therefore, controlling sound pressure levels is deemed an adequate representation of

open water exposures, this has not been tested

empirically. Furthermore, this hypothesis is

based largely on the assumption that compressible tissues, such as the lung, are most

vulnerable to underwater acoustical damage,

when in fact, the most significant effects thus

far observed seem to be either central nervous

or vestibular system effects. The mechanism

for these effects, and thus the relevance of
plane wave acoustics, remains essentially unknown.

Acoustical engineers at the Naval Research

Laboratory (NRL) in Orlando, FL. have designed a method to simulate open water acoustics in a relatively enclosed facility (thereby

maintaining appropriate experimental control)

by using a second source projector to create

trie purely resistive field present in a plane

progressive traveling acoustic wave (Forsythe

and Van Buren, 1995). We used this method

to expose 6 subjects to low-frequency waterborne sound. Apart from the differences in

wave mechanics, the signals used in this experiment were identical to signals used in the

most recent NEDU experiment (Russell and

Knafelc, 1995). That is, the same frequency

characteristics (warble and sweep signals varying from 160-320 Hz), duration of exposures

(9,100 second intervals per dive), duty cycles

(50%), and estimated sound pressure level

(160 dB) were used. Therefore, some direct

comparisons between responses to plane

waves and standing waves can be made.

METHOD

Research Set-up

This experiment took place at Bugg

Spring, FL. Bugg Spring is a funnel shaped

spring with top diameter of 130 m and depth

of 53 m. Water temperature in the spring (below about 5 m) is constant at 22°C at all

depths at all times of the year. The spring is

leased by the Navy, isolated from recreational

activity, and routinely used for underwater sonar testing. Dense vegetation surrounding the

spring and its somewhat isolated location in a

rural area contribute to the low noise levels in

the spring. The ambient noise level is usually

below sea-state-zero on an extrapolated Knudsen curve. Measured sound speed in the

spring is 1488 m/sec at a depth of 15 meters.

Figure 1 is a hydrographic map of the spring.

All diving took place off a barge located

approximately in the center of the spring. Divers entered the water through a central openFigurel. A hydrographic map of Bugg Spring. Indicated depths are in meters. The diving platform was located

over the deepest portion of the spring.
TEST BARGE

A

DIVER

£

60'

-2m- 2mFigure 2. Schematic representation of the diving

set-up. Subjects dove through a central opening in

the test barge. Sound projectors were located

directly in front of and behind the subject when in

position for sound exposure testing.

ing in the barge, and were situated with sound

transducers located approximately 2 meters in

front of and behind them (Figure 2). A trapeze with harnesses was used to maintain the

divers position and control his depth (Figure 3).

Subjects

The subject population consisted of 8 active-duty US Navy divers (6 experimental subjects and 2 controls), possessing Diver Second

Class qualification or higher. Divers were

medically qualified for experimental diving as

determined by review of medical records by

the principal investigator (a qualified Diving

Medical Officer). All subjects were healthy

males (not undergoing medical evaluation or

treatment, and without chronic unresolved

medical disability) between the ages of 24 and

35.

Test Conditions

All underwater sound exposures were conducted using a fixed sound pressure level of

160 dB. The sound pressure level was determined at the diver location without the diver

present (Appendix A is a description of the

sound field production and monitoring methods). Each of the six primary diver-subjects

completed one sound exposure dive per day

for 9 test days. The first exposure dive for all

subjects was conducted at a depth of 30 ft.

All remaining exposures were conducted at 60

ft. The purpose of the 30 ft. dive was to orient the subject to the sound exposure at a shallower depth before proceeding with eight

Figure 3. Schematic representation of diving trapeze

set-up. A,B: primary and compensating sound

sources; C: Osprey video camera for visualization of

the diver during testing; D: nystagmus monitoring

camera mounted to the diver's face mask; E: diver/

medical umbilical (gas supply and ECG electrode

wiring); F: SINDBAD reaction time testing tray.
Table 2

Experimental Design

Unhelmeted

Signal 1

el e2

Signal 2

el e2

Helmeted

Signal 1

el e2

Signal 2

el e2

experimental dives at the single depth of 60 ft.

Two transmission sequences were used, a warble tone signal at 240 +/- 80 Hz (using a 5 Hz

warble rate), and a slow sweep signal from

230 to 320 Hz. The diving rigs used were

grouped into two categories: helmeted, and unhelmeted. The helmeted diving rig for all subjects was a USN MK-21. The unhelmeted

diving rig for four of the experimental subjects and the two control subjects was a USN

MK-20. For the remaining two experimental

subjects, a USN MK-16 (a closed circuit diving rig) was used in the unhelmeted condition.

For the eight 60 ft. dives each subject was exposed under 4 conditions with 2 exposures per

condition in a repeated measures design as

shown in Table 2, where "e 1" represents exposure number 1 for each condition, and "e 2"

represents exposure number 2 (the repeated

measure).

In order to separate a cumulative exposure

effect from an effect of a specific condition,

the sequence of exposure conditions were

counterbalanced between subjects (Table 3).

Transmission sequences were delivered as

9 successive continuous sound intervals of

100 seconds each. Each sound interval was

followed by an equal time inter-pulse interval

during which no sound was transmitted.

Thus, subjects received a cumulative underwater sound exposure of 15 minutes per dive.

Table 3

Diving Schedule

Date

17-M-95

18-M-95

19-M-95

20-M-95

21-M-95

24-M-95

25-M-95

26-M-95

27-M-95

51 = Unhelmeted, Signal 1

52 = Unhelmeted, Signal 2

Diver

Day Dl D2 D3 D4 D5 D6

30 ft. orientation dive for all divers

1 SI S2 S3 S4 S2 S3

2 S2 SI S4 S2 S3 S2

3 S3 S4 S2 SI SI S4

4 S4 S3 SI S3 S4 SI

5 S4 S3 SI S3 S4 SI

6 S3 S4 S2 SI SI S4

7 S2 SI S4 S2 S3 S2

8 SI S2 S3 S4 S2 S3

S3 = Helmeted, Signal 1

S4 = Helmeted, Signal 2
For each dive, the following schedule was

used:

(1) Establish and verify sound signals and

levels.

(2) Diver enters water, surface checks performed, begins descent.

(3) Diver reaches bottom, signals ready.

(4) Signal turned on for 100 seconds. Diver

performs testing during the sound exposure (see below).

(5) Signal turned off for 100 seconds. Directed conversation with diver. Diver

asked if ready to proceed with next exposure.

(6) If diver OK, repeat steps 4 and 5 for a total of 9 exposures.

(7) End of ninth exposure. Diver leaves bottom.

(8) At surface, diver removes diving rig,

ECG leads, and wet suit, then is immediately turned over to medical personnel for post-exposure testing.

The two control subjects completed one 30

ft. dive (unhelmeted), and eight 60 ft. dives (4

helmeted, 4 unhelmeted) without sound exposure. All divers wore 1/4-1/2 inch wet suits

including hoods, gloves, and booties.

The diving operations for this experiment

were conducted in strict accord with the US

Navy Diving Manual (1993). A standby diver

was present during each dive (ready to enter

the water to assist a compromised diver). An

underwater video camera was used to maintain visual contact with the diver at all times

during exposures. Verbal communication between topside personnel and the diver was

also maintained throughout the dive, with line

pull signals used as backup. On site access to

a dry treatment recompression chamber was

provided. A Diving Medical Officer and a

Diving Medical Technician were on site at all

times during diving operations. Appendix B

is a copy of the dive protocol.

Assessment ofhealth andperformance

Before and after the dive series, each diversubject completed the following:

(1) General medical history and review of

systems with emphasis on vestibular and

neurological history, and physical examination with emphasis on neurological examination.

(2) Pulmonary function testing (Appendix C).

(3) Two clinical audiograms.

(4) Neuropsychometric testing (Appendix D).

(5) Electroencephalogram (EEG), brain mapping (Appendix D).

(6) Quantitative oculomotor performance battery; Micromedical Technology

VORTEQ system (Appendix D).

(7) Balance platform performance, Neurocom Pro Balance Master (dynamic posturography) as modified by Naval

Aerospace Medical Research Laboratory

(NAMRL) (Appendix D).

All baseline tests were performed within 1

week prior to the first underwater sound exposure. Baseline tests were performed for comparative purposes in the event of a symptomatic response from the sound exposures. All

post study testing was performed within 1

week following the final sound exposure to es-
tablish the divers well being at the end as compared to the beginning of the study.

Prior to and immediately after each dive,

diver-subjects completed the following:

(1) Fitness to dive physical examination, as

indicated by history.

(2) Dynamic visual acuity testing (DVAT)

(Appendix D).

(3) Balance platform testing, Neurocom Pro

Balance Master (dynamic posturography) as modified by Naval Aerospace

Medical Research Laboratory

(NAMRL) (Appendix D).

(4) Audiogram for hearing thresholds at 250,

500,1000, 2000, 4000, and 8000 Hz

(Appendix E).

Pre and post-exposure testing was designed to efficiently assess the diver's acute

response to the underwater sound exposures

with emphasis on possible auditory, vestibular, and central nervous system effects.

During each dive, diver-subjects were

monitored using the following:

(1) Systematic Investigation of Navy Diving

Behavior at Depth (SINDBAD) sustained performance key insertion test for

the initial 60 seconds of each 100 second sound exposure (Appendix F).

(2) Real time in water videooculography

(VOG) during the final 30 seconds of

each 100 second sound exposure using a

Mini B&W camera, model UWC-120,

Outland Technology Inc.; ISCAN pupillary reflection eye tracking system; and

Video time based corrector (Appendix

D).

(3) Continuous electrocardiograms (ECG).

(4) A symptoms survey during each sound

exposure (Appendix G).

These tests were designed to monitor the

subjects responses during the actual sound exposure for early detection of compromise, or

other adverse effects.

All testing, with the exception of one of

the clinical audiograms and the neuropsychometric testing, was conducted at the test

site using portable equipment, and trained

technicians under the supervision of qualified

medical officers. All subjects received pre

and post study audiograms at the Naval Medical Clinic in Orlando, as well as at the test

site. Neuropsychometric testing took place at

the Naval Aerospace Medical Institute

(NAMI) in Pensacola.

Dive Termination Criteria

The following termination criteria were

used during the underwater sound exposures:

(1) upon request by the subject for any reason,

(2) as video nystagmus monitoring abnormalities indicate when correlated with

subjective symptoms,

(3) presence of any significant discomfort or

pain,

(4) as determined by the diving officer, diving supervisor, diving medical officer,

or principal investigator,

(5) cessation of the SINDBAD test during an

exposure for no known reason,

(6) Loss of video, and/or voice communication.
Because the possible effects of the sound

exposure are wide and varied, continued exposures were based on the determination of a

"compromised diver" rather than a particular

symptomatology.

A "compromised diver" was defined as

any diver whom, in the opinion of the diver,

diving officer, diving supervisor, diving medical officer, or principal investigator could become a casualty or burden to others in an

operational setting as a result of the sound exposure.

If the "compromised diver" had symptomatology that was self-limiting, spontaneously

recovered after the sound was turned off, resulted in no subjective or objective after-effects, and was without risk for harm to the

diver in the controlled setting of the experiment, then this was considered a "minor" compromise.

A "major" compromise was defined as a

diver with symptomotology that required supportive measures for recovery from the insult,

required prolonged recovery time, or resulted

in minor after-effects (as determined by the

medical monitor).

A "catastrophic" compromise was defined

as a diver whose symptomatology resulted in

risk of "life or limb," or major after-effects (as

determined by the medical monitor).

A flow chart of continued testing in the

event of a compromised diver is presented in

Appendix H. A major compromise would result in termination of testing at 160 dB. Testing would resume at 154 dB. Two minor

compromises were required before testing

was terminated at 160 dB and then continued

at 154 dB.

— SPL (Without diver in position)

— Diver I

Diver 2

-- Diver 3

200 300

Frequency in Hz

I80-

ut diver in position B

Diver 1

I60- p-WI50-

1 40-

I30- y-s-.

120-

1 IO-

^f

200 300 1

Frequency in Hz

-

't

- SPU (Without diverin

- Diver 4

Diver 5

- Diver 6

position )

\

v

c

i

200 300

Frequency in Hz

Figure 4. Sound pressure level diagrams showing

sound pressure as a function of frequency with and

without divers present for both warble tone (A and

C), and sweep tone (B) signals. Note that the typical

response to the presence of a diver in t he sound

field was an attenuation of the sound pressure level

by 5-10 dB (A and B). However, diver 4 had an

effect of actually increasing the sound pressure

level for the lower frequency component of the

warble tone (C). See text for explanation.

10
RESULTS

Soundfield characteristics

Figures 4A and B are sound pressure level

diagrams for the warble and sweep tone signals, respectively, with and without divers present in the field. These measurements were

taken from a hydrophone located approximately 40 cm to the left of where the diver

was during an exposure. As can be seen, the

sound pressure level for both signals was

nearly constant at 160 dB without the diver

present. The transducer output was set at this

level and unaltered during exposures of the divers (see Appendix A for details). With a

typical diver-subject present during an exposure, the sound pressure level is attenuated

some 5-10 dB by the presence of the diver.

This was seen with both signals, both helmeted and unhelmeted diving rigs, and at both

30 and 60 ft. depths. However, one subject

(as seen in Figure 4C) had the effect of increasing the sound pressure level for the

lower frequency component of the warble

tone signal at 60 ft. This effect was not seen

at 30 ft., but was seen in both the helmeted

and unhelmeted diving rigs. Further inquiry

revealed that this subject was wearing different wet suit material than the other subjects.

Specifically, he wore 1/8" thinsulate with lycra undergarment covered by 1/8" neoprene

for a total of 1/4" wet suit material, while the

remainder of subjects wore 1/4" neoprene nitrogen blown closed cell rubatex in two pieces

(a "farmer John" for legs and chest, and a

hooded jacket for arms, head, and chest, resulting in 1/2" neoprene over the chest area).

After all subject exposures had been completed, the effect of the wet suit materials

alone (without the diver present) on the sound

field was tested. Figures 5A and B show the

effect of the 1/4" neoprene worn by most divers. The result is an attenuation of 8-10 dB.

Therefore, the attenuation seen with the divers

present was essentially accounted for by the

wet suit material alone. Likewise, when the

1/8" thinsulate/lycra plus 1/8" neoprene was

tested, the same response seen for the diver

represented in figure 4C was observed (Figures 6A and B). That is, there was an increase

in intensity of the low-frequency component

of the warble tone signal. Separating the thinsulate/lycra from the neoprene revealed that

the effect was the result of the 1/8" neoprene

Without wet suit

With wet suit

200 3O0

Frequency in Hz

suit B

With wet suit

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£

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=

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200 300

Frequency in Hz

Figure 5. Sound pressure level diagrams with and

without 1/4" neoprene nitrogen blown closed cell

rubatex two piece wet suit alone (no diver) for both

warble tone (A), and sweep tone (B) signals. This is

the wet suit material worn by the divers represented

in Figures 4A and B. Note that the 5-10 dB

attenuation of sound pressure level seen in Figures

4A and B with divers present in the field is

accounted for by the wet suit material alone.

11
suit

t

A

I70-

Withwetsu

I60-

I50 -

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Frequency in Hz

B

With wet suit

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£ \\

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£

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200 300

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out wet suit c Withwet suit

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E ■■-.. ~~ "

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£ // \\

-§ I40- V»

£ I \\

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</

^

200 300

Frequency in Hz

Figure 6. Sound pressure level diagrams with and

without 1/8" thinsulate with lycra undergarment

covered by 1/8" neoprene wet suit (no diver) for

both sweep tone (A) and warble tone (B) signals.

This is the wet suit material worn by "diver 4" in

Figure 4C. The effect of the 1/8" neoprene without

the undergarment is also shown (C). Note that,

again, both the attenuating and enhancing effects

seen in Figure 4C are accounted for by the neoprene

wet suit material alone.

alone (Figure 6C). The tentative interpretation is that at 60 ft. a bubble-like resonance of

approximately 160-180 Hz is stimulated in the

1/8" neoprene wet suit material.

Effects on Divers

Fifty four manned dive exposures were

completed using six subjects. In addition,

eighteen manned dives without sound exposure were completed using two subjects. An

initial eight manned dives without sound exposure were also completed using all eight subjects prior to the first sound exposure dive. At

no time during these dives was a "compromised diver," as defined above, identified.

There were no dives terminated early due to

effects of the sound exposures.

Pre- and Post-study Testing:

Pre- and post-study audiograms obtained at

the Naval Medical clinic in Orlando were

judged not to be of clinical quality (250 and

8000 Hz frequencies were not tested, and several subjects complained that background ambient noise and inadequate facilities interfered

with testing). Therefore, effects on hearing

were assessed from on-site audiometric measurements only (see below).

Medical monitors did not note any clinically relevant changes in physical examinations of subjects post-study compared to

pre-study. In particular, neurological exams

were unchanged.

No decrements in pulmonary function

were detected post-study (mean

FEV1/FVC=78.2%) compared to pre-study

(mean FEV1/FVC=77.3%; p=.266 for a

paired sample t-test of the two means).

Appendix I is a summary of pre- and poststudy test results for electroencephalogram

(EEG) and vestibular function (dynamic platform posturography and quantitative oculomotor performance battery) testing. For EEG

12
REP 2 REP 3 REP 4

BASELINE REPETITIONS

1250 Hz 500 Hz A 1000 Hz D 2000 Hz O 4000 Hz 0 8000 Hz

REP 2 REP 3 REP 4

BASELINE REPETITIONS

I «250 Hz »500 Hz A 1000 Hz D 2000 Hz 04000 Hz A 8000 Hz |

Figure 7. Results of five repeated audiograms used

to establish a baseline level of hearing threshold.

Depicted is the mean threshold level across eight

subjects for the six frequencies used in audiogram

testing for both right and left ears. Note that there is

very little variation between repeated test results,

indicating good test to test reliability in audiogram

measurements.

testing, all pre- and post-study measurements

were within clinically normal limits. No

changes were observed during the running

memory task portion of EEG testing, but three

of the six experimental subjects did show

some increase in alpha wave activity in temporal/parietal areas during the resting state poststudy compared to pre-study. This effect was

not observed in either of the control subjects.

However, since the post-study results were

still within normal limits, the clinical significance of these changes is uncertain. The

trend for all subjects (experimental and control) in both dynamic platform posturography

and quantitative oculomotor performance battery testing was toward improvement in vestibular function during post-study testing

compared to pre-study testing. This may represent a modest learning effect for the vestibular function testing procedures during the

course of the experiment (see below).

Appendix J is a summary of pre- and poststudy neuropsychological assessments. All

statistically significant changes were in the direction of improvement for post-study scores

compared to pre-study scores.

Pre and Post-exposure Testing:

For audiogram and balance platform testing, training sessions were used to limit the effects of learning during the exposure trials.

All subjects had performed audiograms in the

past (during prior experiments involving

audiogram testing, and/or during physical exams for diving qualifications). Therefore, it

was anticipated that minimal training (two

practice sessions) would be required to eliminate a learning effect. The results of five baseline audiograms (means across subjects)

following the two practice audiograms are

shown in Figure 7. As evidenced by the flatTRIAL NUMBER

Figure 8. Results (means across eight subjects) of

six repeated balance platform tests during subject

training sessions. The test depicted is the most difficult of the balance platform maneuvers with eyes

closed, a sway platform, and head movements (EC/

SS/HM). Scores indicate % of maximum stability,

with a score of 100 representing perfect stability,

and a score of 0 representing a fall. Note that test

performance is highly dependent of familiarization

training, but that the greatest learning effect occurs

between the first and second practice trials, with

relative flattening of the learning curve thereafter.

13
MEAN ACROSS SIX TEST FREQUENCIES MEAN ACROSS SIX TEST FREQUENCIES

SUBJECT I

SUBJECT 2

A SUBJECT 3

D SUBJECT 4

SUBJECT 5

SUBJECT 6

A SUBJECT 7

D SUBJECT 8

4 5 6 7

DIVE DAYS

Figure 9. Pre-exposure trend for audiogram testing. Day to day variation in pre-sound exposure hearing

thresholds (means across the six test frequencies) for each subject are shown. The relative flatness of the curves

indicates that repetitive testing had little effect on audiogram results.

ness of these curves, there appeared to be no

learning effect during these five trials. In contrast, since none of the subjects had prior familiarization in balance platform testing, it

was anticipated that a greater degree of training (an estimated minimum of five training

sessions) would be needed to reach a level of

peak performance on the balance platform.

Figure 8 shows the results (means across subjects) of 6 training trials for the most difficult

of the balance platform tests (eyes closed,

head movement, sway platform); the test

showing the greatest learning effect. Although a clear learning effect is demonstrated,

the most significant improvement occurred between the first and second trials with the mean

score increasing from 25.6 to 51.1 (scores indicate % of maximum stability, with a score

of 100 representing perfect stability, and a

score of 0 representing a fall). Between the

second through sixth trials, however, there

was considerably less variation with a low

mean score of 50.1 occurring during the

fourth trial, and a high mean score of 57.1 during the sixth trial. There were no direct training sessions for the dynamic visual acuity test

(DVAT), although similar testing was included as part of the pre-study quantitative

oculomotor performance battery.

The trend of pre-exposure test results was

analyzed for learning effects and test re-test reliability. Figure 9 shows the day to day pre-exposure hearing threshold (mean across

frequencies) for each of the eight subjects.

The R

2

correlation statistics for these curves

are less than 0.1 indicating that the audiogram

results were relatively independent of the test

days on which they were completed. The

trend of pre-exposure results for the balance

platform tests are represented in figures 10A,

10B, IOC, and 10D. Figure 10A and 10B represents the trend for the easiest test (eyes

open, no head movement, stable platform).

The R

2

correlation statistic was less than 0.01,

again illustrating that the test result was independent of the test day. For the most difficult

balance platform test (eyes closed, head movement, sway platform) a slight trend of improvement is seen (figures 10C and 10D).

The R

2

correlation statistic for this test was

0.14. This may represent some degree of continued learning throughout the experiment for

the more difficult balance platform maneuvers. This effect is, however, relatively small

in relation to clini-cally significant differences

in performance. Figures HA, 11B, 11C, and

11D show the pre-exposure trends for two of

the DVAT tests used in this experiment (the

easiest, 0 d/s head movement, and the most

difficult, 200 d/s head movement). In general,

14
EO EO

100-

80-

60-

40-

20-

0-

SUBJECT I

=S=e==&:

-H -+- +- -+-

3 4 5 6

DIVE DAY

SUBJECT 2 a SUBJECT 3 SUBJECT 4

100-

80-

60-

40-

20-

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SUBJECT 5

3 4 5 6

DIVE DAY

SUBJECT 6 a SUBJECT 7

EC/HM/SS

100

80-

EO

40

20

0

3^

SUBJECT I

3 4 5 6 7 8 S

DIVE DAY

I SUBJECT 2 a SUBJECT 3 D SUBJECT 4

<r 100-1

o

o 80-

en

>

60-

40-

m 20-

-+- -+-

4 5 6

DIVE DAY

SUBJECT 5 »SUBJECT 6 ÖSUBJECT7 SUBJECT 8

Figure 10. Pre-exposure trend for balance platform testing. Day to day variation of subjects' pre-sound exposure stability scores for the easiest (A) and most difficult (B) balance platform tests are shown. The day to day variability ws

greater for the more difficult test, but overall, subjects scores remained relatively consistent throughout the experiment.

EO: eyes open, no head movement, stable platform; EC/HM/SS: eyes closed, head movement, sway platform.

Od/s

SUBJECT I

4 5

DIVE DAY

SUBJECT 2 A SUBJECT 3

Od/s

D SUBJECT 4

SUBJECT 5

5

DIVE DAY

SUBJECT 6 a SUBJECT 7

200 d/s

» SUBJECT I

4 5

DIVE DAY

I SUBJECT 2 A SUBJECT 3 SUBJECT S

4 5

DIVE DAY

SUBJECT 6 A SUBJECT 7

Figure 11. Pre-exposure trend for dynamic visual acuity testing (DVAT). Day to day variation of subjects'

pre-sound exposure test results for the easiest (A) and the most difficult (B) DVAT tests are shown. Similar to the

balance platform results, day to day variability was greater for the more difficult test, but, again, the repetitive

testing design did not appear to greatly influence test results, d/s: degrees per second of head rotation.

15
EXPERIMENTAL (SOUND EXPOSED) SUBJECTS EXPERIMENTAL ( SOUND EXPOSEO) SUBJECTS

IOOO 2000

FREQUENCY(kHz)

DAY 2 A DAY 3 DAY 4 O DAY 5

IOOO 2000

FREQUENCY (kHz)

DAY 6 DAY7 A DAYS D DAY 9

CONTROL (NO SOUND EXPOSURE) SUBJECTS CONTROL (NO SOUND EXPOSURE) SUBJECTS

TI000 2000

FREQUENCY (kHz)

DAY 2 A DAY 3 G DAY 4 O DAY 5

IOOO 2000

FREQUENCY (kHz)

DAY 6 O DAY7 A DAYS

Figure 12. Hearing threshold shifts (means across subjects) calculated from post-exposure audiograms for

experimental (A) and control (B) subjects. The different curves represent the nine sound exposure test days.

these plots show a slight day to day improvement in DVAT scores indicative of some continued learning throughout the study, but

again R

2

is less than 0.1 for all DVAT tests,

and thus the effect was relatively small.

Figures 12A and B show mean hearing

threshold shifts (post vs. pre exposure

audiogram results) for experimental and control subjects, respectively. Repeated measures

ANOVAs with three factors were conducted.

Factors included diving rig (helmeted or unhelmeted), sound characteristics (warble or

sweep tone), and time (pre- or post-exposure).

There were no main effects for diving rig or

sound characteristics, and no significant interactions. For the experimental subjects, thresholds were significantly higher post-exposure

compared to pre-exposure for the left ear at

250 (p=.028), 500 (p=.048), and 1000 Hz

(p=.045), and for the right ear at 4000 Hz

(p=.031). Although statistically significant,

these threshold shifts were small (5 dB or

less), and thus the clinical significance of such

changes is questionable. Furthermore, confounding factors apart from the sound exposures may have contributed to these

differences. Specifically, three experimental

subjects experienced ear squeezes during the

course of the study, and one subject was exposed to very loud microphone feedback during a dive. The two control subjects showed

no significant changes between pre- and postexposure hearing thresholds.

Figures 13-15 show the pre- and post-exposure results for balance platform and DVAT

testing. Three factor (diving rig, sound characteristics, and time) repeated measures ANOVAs were conducted. For the overall balance

platform score, there were no significant main

effects, but there was a significant sound characteristic and time interaction (p=.018). For

the warble tone, there was a greater degree of

improvement in post-exposure scores (compared to pre-exposure scores) than for the

16
100

90-

80

70

60

w 50-

40-

30-

20-

rt & fefi A

ifo

AVERAGE PRE

0 AVERAGE POST

EC EO/HM EC/HM EC/SS EC/HM/SS

BALANCE PLATFORM TEST FORMAT

70-

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50-

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AVERAGE PRE

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EC EO/HM EC/HM EC/SS EC/HM/SS

BALANCE PLATFORM TEST FORMAT

100

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£ 60

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30

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AVERAGE PRE

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BALANCE PLATFORM TEST FORMAT

90

80

70

60

50

40

30

20

10

i*A

ki-r

a* ft rfA

|i& A

I I AVERAGE PRE

[3 AVERAGE POST

EO/HM EC/HM EC/SS EC/HM/SS

BALANCE PLATFORM TEST FORMAT

Figure 13. Comparison of pre- and post-exposure balance platform scores (mean across subjects) for experimental

(sound exposed) subjects under the four diving conditions. (A) Condition 1 - unhelmeted, warble signal; (B) Condition 2 - unhelmeted, sweep signal; (C) Condition 3 - helmeted, warble signal; (D) Condition 4 - helmeted, sweep

signal. EO: eyes open, no head movement, stable platform; EC: eyes closed, no head movement, stable platform;

EO/HM: eyes open, head movement, stable platform; EC/HM: eyes closed, head movement, stable platform;

EC/SS: eyes closed, no head movement, sway platform; EC/HM/SS: eyes closed, head movement, sway platform.

sweep tone signal. For the individual balance

platform tests, the two least difficult (no head

movement and a stable platform with eyes

open, and eyes closed), and the two most difficult (eyes closed and an unstable platform

with head movements, and without head

movements) showed no significant main effects and no significant interactions. For the

two mid level difficulty tests (head movement

and a stable platform with eyes open, and

eyes closed), however, both showed statistically significant results. For the eyes open

with head movement test, significant effects

for diving rig (p=.019), and time (p=.005)

were observed with no significant interactions. Post-exposure scores were improved

compared to pre-exposure scores, and scores

following the unhelmeted condition were

higher than those for the helmeted condition.

For the eyes closed with head movement test,

17
I I AVERAGE PRE

C^H AVERAGE POST

STATIC ?0d/» lOOd/t I40d/s

DVAT TEST FORMAT

-0.05-

-0.1 -

-0.15-

1 I AVERAGE PRE

C<H AVERAGE POST

LS^ -^br

STATIC 70d/s lOOd/i 140d/* 200d/s

DVAT TEST FORMAT

-0.05

-0.1 -

-0.15

I 1 AVERAGE PRE

pH AVERAGE POST

1 "¥L-I^l I^' >l I ' "^ ' '" I

STATIC 70d/s lOOd/s I40d/t 200d/s

DVAT TEST FORMAT

0.3-

0.Z5

0.2 -

0.15

I I AVERAGE PRE

PH AVERAGE POST

IP a.

TOd/i I00d/s (40d/*

DVAT TEST FORMAT

Figure 14. Comparison of pre- and post-exposure dynamic visual acuity scores (mean across subjects) for

experimental (sound exposed) subjects under the four diving conditions. (A) Condition 1 - unhelmeted, warble

signal; (B) Condition 2 - unhelmeted, sweep signal; (C)_ Condition 3 - helmeted, warble signal; (D) Condition 4 -

helmeted, sweep signal, d/s: degrees/second of head rotation.

there were no significant main effects for diving rig or sound characteristic, but there was a

significant effect for time (p=.034). In addition there were significant diving rig and time,

and sound characteristic and time interactions

(p=.022, and p=.034, respectively). Again,

post-exposure scores were improved compared to pre-exposure scores. The time effect

was greater for the helmeted condition compared to the unhelmeted condition, and for the

warble tone compared to the sweep tone.

For the DVAT test, there were no significant main effects for diving rig, sound characteristic, or time. In addition, apart from one

significant diving rig and sound interaction

for the 70 degree/second test (p=.036), there

were no significant interactions.

The two control subjects showed no statistically significant changes in balance platform

or DVAT testing.

To summarize the pre- and post-exposure

vestibular testing results, very little change in

vestibular function was observed. The

changes that were seen were in the direction

of improved function following the sound exposure dives.

During Exposure Testing:

The videooculography revealed no evidence of nystagmus in response to the sound

exposures. Appendix K is an abstract summarizing these results.

Results of the SINDBAD key insertion test

are summarized in Figures 16A and B. Subjects were given 9 practice trials prior to test18
rä Slti

1% Aft

O AVERAGE PRE

C3 AVERAGE POST

EC EO/HM EC/HM EC/SS EC/HM/SS

BALANCE PLATFORM TEST FORMAT

itö fa I* TÄ

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ft

I I AVERAGE PRE

C3 AVERAGE POST

EC EO/HM EC/HM EC/SS EC/HM/SS

BALANCE PLATFORM TEST FORMAT

0.3

0.25

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0.15

-0.05

-0.1

-0.15

-0.2 J

| I AVERAGE PRE

m AVERAGE POST

"W I

STATIC 70d/« lOOd/» I40d/s 200d/s

DVAT TEST FORMAT

0.3-

0.25- \ I AVERAGE PRE

rp7] AVERAGE POST

id

TO

+J= h

STATE 70d/l lOOd/s I40d/i 200d/s

DVAT TEST FORMAT

Figure 15. Comparison of pre- and post-exposure balance platform and dynamic visual acuity scores (mean across

subjects) for control (no sound exposure) subjects. (A) Balance platform, unhelmeted; (B) Balance platform,

helmeted; (C) Dynamic visual acuity, unhelmeted; (D) Dynamic visual acuity, helmeted. EO: eyes open, no head

movement, stable platform; EO/HM: eyes open, head movement, stable platform; EC/HM: eyes closed, head

movement, stable platform; EC/SS: eyes closed, no head movement, sway platform; EC/HM/SS: eyes closed, head

movement, sway platform, d/s: degrees/second of head rotation.

4-

B

3-

£

Z

<

UJ

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2-

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0'« <v>e

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10 20 30 40 50 60 70 80 90

TRIAL

10 20 30 40 50 60 70 80 90

TRIAL

Figure 16. SINDBAD results. Depicted are reaction times (mean across subjects) of experimental (A), and control

(B) subjects. The horizontal line of each diagram represents the mean reaction time across subjects for the final

practice trial. This time was used as a baseline for comparison during the sound exposure dives. Each subject

performed 9 test trials during each of the 9 sound exposure dives for a total of 81 test trials. Note the gradual

improvement in reaction times for both experimental and control subjects with the increase in the number of test

trials performed. This improvement, however, was offset in both experimental and control subjects by a

corresponding increase in the number of errors made during testing (not shown)

19
SUMMARY HEART RATE DATA

120

100-

80

c

e

^ 60

I

40

20

0'

'-D-a-o

D-D

D

-,.Q

ooo-cO EXPERIMENTAL SUBJECTS

D CONTROL SUBJECTS

I I 3 I 5 I 7 I 9 I II I 13 I 15 I 17 I

2 4 6 8 10 12 14 16 18

RECORDING SEQUENCE

Figure 17. Summary heart rate data for experimental

and control subjects. Heart rates were recorded at six

separate times (two before sound, three during sound,

and one after sound) for three of the nine sound exposure sequences during each dive. The curves represent

the mean heart rates for experimental and control

subjects. The peaks in each of the curves corresponds

to the SINDBAD reaction time testing. The sound

exposures did not appear to affect heart rate.

ing. The final score of the practice trials was

used as a baseline for comparison. Subjects

(both controls and experimental) showed a

gradual improvement in response time

throughout the study. However, this improvement in response time was offset by a corresponding gradual increase in the number of

incorrect responses where the key was not

properly inserted. The likely explanation for

these results is that subjects, to offset the monotony of the testing procedure, used the

SINDBAD test to compete with each other.

Since the major feedback given to the subjects

was response time, their efforts were concentrated on doing the test as fast as possible resulting in improved times, but with more

mistakes being made. Overall, the sound exposure had no noticeable effect on SINDBAD

testing.

ECG monitoring revealed no direct effects

of the sound on heart rate or rhythm. However, a predictable elevation of heart rate was

observed corresponding to the SINDBAD testing during each sound exposure. Heart rates

were recorded around 3 of the 9 sound exposures of each dive (the first, the fourth, and

the seventh). For each of these exposures

heart rates were recorded at six separate

points (two before the exposure, three during

the exposure, and one after the exposure).

Heart rates increased at the beginning of the

sound exposure (also the beginning of the

SINDBAD testing), peaked at the 40 second

point during the exposure (sound on, performing SINDBAD), and returned to baseline at

the 80 second point in the exposure (sound

on, but not performing SINDBAD). This

heart rate response also occurred in the two

controls who were not exposed to the sound.

Figure 17 is a summary of the heart rate data.

Appendix G is a copy of the symptoms survey with a modified Borg scale used during

each exposure. Responses with scores greater

than 0 were given only for questions 1,4, 6,

10,11, and 12. All subjects gave a positive response to questions 1 and 4 (sensation of vibration). Scores for vibration sense ranged

from 0 to 3 (moderate sensation), and were located primarily in the extremities and chest region, with a few isolated responses of

sensations in the head and neck region. Only

one diver reported not feeling wide awake and

alert (question 6) during a sound exposure.

This diver responded with a 1 (very slight) on

three occasions during two dives (during the

fifth exposure of one dive and during the

eighth and ninth exposures of a second dive).

He also reported that the sound seemed to contribute to the symptom. This same diver was

also the only subject to give a non-"0" score

to question 10 (inability to concentrate). He

gave a .5 to 1 (very, very to very slight) response for the last two to four exposures of

four separate dives. Again, the sound seemed

20
to contribute to the symptom. Two divers reported brief unusual sensations (question 11).

One diver reported a 2 (slight) for a sensation

of turning to the left while looking down during a sound exposure. The sensation was a

slow 90° rotation over approximately 5 seconds, and was broken by looking up. This occurred during this diver's orientation exposure

at 30 ft., but not during his 8 subsequent dives

with sound exposure at 60 ft. Another subject

reported a sensation of gastrointestinal gas

build-up associated with sound exposures during one dive. Finally, four of the divers reported .5 to 3 (very, very slight to moderate)

to question 12 (annoyance). In general, the

annoyance scores were higher and more frequent for the sweep signal in the unhelmeted

diving rig.

Underwater BreathingApparatus Performance

There were no reports of problems with

any of the rigs during the sound exposures. In

addition, post dive procedures did not reveal

any mechanical defects in the diving rigs following the sound exposures.

Conclusions

Fifty-four manned exposures (6 orientation

dives, and 48 test dives) to two low-frequency

underwater acoustic signals were performed.

Both helmeted and unhelmeted diving rigs

were used. The primary depth of exposure

was 60 ft.

results are confounded by circumstances unrelated to the water-borne sound exposures,

such as ear squeezes from diving. Pre and

post-exposure vestibular testing showed that

vestibular function in subjects exposed to

water-borne sound under the conditions of

this experiment is not adversely affected.

During exposures, videooculography, ECG

monitoring, and SINDBAD performance revealed no adverse effects of the sound exposures. Symptoms surveys during exposures

showed that divers may become moderately

annoyed by such exposures, but overall found

the exposures tolerable. Annoyance was

slightly greater in the unhelmeted condition

with the sweep tone signal.

Sound field testing revealed that neoprene

wet suits generally act to attenuate low-frequency sound exposures, but under certain circumstances may also accentuate a sound

exposure. This may be due to resonance effects within the wet suit material.

There is no indication from the results of

this study that low-frequency water-borne

sound exposures (using the sound wave characteristics as described in this experiment) in

the open water (plane wave acoustics) present

any additional risk compared to similar exposures in enclosed environments (standing

wave acoustics), such as the ocean simulation

facility at the Navy Experimental Diving Unit.

There were no sound related events during

the dive series compromising the diver's

health or safety. Pre and post-study examinations of subjects also revealed no clinically

significant detrimental effects resulting from

exposure to low-frequency water-borne sound

under the conditions of this experiment.

Pre and post-exposure audiograms show

some slight decrements in hearing, but these

References

Bolanowski, S. J. (1994). Assessment ofthe

effects of250 Hz vibratory stimuli applied

to the cutaneous sensory system as they relate to sensation, pain, and discomfort.

Syracuse, NY: Syracuse University, Institute for Sensory Research.

21
Crum, L. A. & Mao, Y. (1996). Acoustically

enhanced bubble growth at low frequencies and its implications for human diver

and marine mammal safety. Journal ofthe

Acoustical Society ofAmerica, 99(5),

2898-207.

Forsythe, S. E. & Van Buren, A. L. (1995).

Proposed experiment to produce a region

oflow-frequency plane wave using two

sphericalprojectors. (Report submitted to

NSMRL, Feb 94).

Lehner, N. D. M. (1994). Response ofthe

lungs to lowfrequency underwater sound:

swine studies. (Report submitted to

NSMRL).

Nyborg,W. L. (1993). Estimates of limits to

temperature rise. Appendix In F. M. Pestorius (Au), Effects oflowfrequency waterborne sound on divers (Tech Report

ARL-TR-96-5). Austin, Texas: University of Texas at Austin, Applied Research

Laboratory.

Rogers, P. H., Caille, G. W., & Lewis, T. N.

(1994J. Response ofthe lungs to lowfrequency underwater sound (Presentation at

NSMRL meeting, Effects of low-frequency water-borne sound on divers: Summary Meeting, 29 Jun 94). Groton, CT:

Naval Submarine Medical Research Laboratory.

Russell, K. L. & Knafelc, M. E. (1995). Low

frequency water-borne sound manned

dive series (Technical Report No. 10-95).

Panama City, FL: Navy Experimental

Diving Unit.

Smith, P. F. (1993). Interview with a diver

exposed to intense low-frequency waterborne sound (NSMRL Memo dtd 25 Feb

93). Groton, CT: Naval Submarine Medical Research Laboratory.

Smith, P. F., Sylvester, R., Baran, F., &

Steevens, C. C. (1996). Development of

a general hearing conservation standard

for diving operations: ExperimentI - Comparison oftemporary auditory threshold

shifts induced by intense tones in air and

water (NSMRL Report 1203). Groton,

CT: Naval Submarine Medical Research

Laboratory.

Steevens, C. C, Knafelc, M. E., & Clarke, J.

(1994). Effects oflow-frequency waterborne sound on divers: Physiological

monitoring during immersion at depth.

Manuscript in preparation.

Steevens, C. C, Russell, K. L., Knafelc, M.

E., Dutka, A. J., Hopkins, E. W., & Smith,

P. F. (1997). Neuropsychological disturbances in divers exposed to intense waterborne sound: Two case reports.

Manuscript submitted for publication.

Steevens, C. C, Schlichting, C. L., & Baran,

F. (1994). Effects oflow-frequency waterborne sound on divers: physiological

monitoring during torso immersion.

Manuscript in preparation.

Suki, B., Habib, R. H., & Jackson, A. C.

(1994). Effects oflow frequency (f <300

Hz) waterborne sound on divers: Wave

propagation in the airways (Presentation

at NSMRL meeting, Effects of low-frequency water-borne sound on divers, 29

Jun 94). Groton, CT: Submarine Medical

Research Laboratory.

Naval Sea Systems Command. (1993). US

Navy Diving Manual Volume 1 (air diving) and Volume 2 (mixed-gas diving)

(NAVSEA 0994-LP-001-9010 and 0994-

LP-001-9020, Revision 3, dtd 15 Feb 93).

Washington, DC: Naval Sea Systems

Command.

22
Verillo, R. T., Bolanowski, S. J., Baran, F. &

Smith, P. F. (1996). The effects of underwater environmental conditions on vibrotactile thresholds. Journal ofthe

Acoustical Society ofAmerica, 100(1),

651-658.

23
[Blank Page]

24
OPEN WATER TRIALS

APPENDICES

Appendix A Sound Exposure Setup and Calibration.

Fig. Al. Signal chain for transmitting and receiving equipment

Fig. A2. Grounding scheme

Fig. A3. Graphical representation of the cancellation effect in polar

coordinates.

Fig. A4. Measurement points in the diver test area.

Fig. A5. Pressure gradient required for compensation transducer.

Appendix B The Dive Protocol.

Appendix C Spirometry Testing.

Appendix D Neuropsychological/Neurological Testing Procedures.

Appendix E Procedure for Administering Audiograms.

Fig. El. Equipment Setup.

Appendix F SINDBAD Sustained Attention Test.

Appendix G Symptoms Survey.

Appendix H Continued Testing.

Fig. HI. Flowchart

Appendix I Neurological Testing. Pre/Post Study Test Results.

Appendix J Neuropsychological Testing. Pre/Post Study Test Results.

Appendix K Abstract Summarizing Results of Videooculography.
[Blank Page]

Appendices

ii
APPENDIX A

SOUND EXPOSURE SETUP AND CALIBRATION

Transmitting setup

The two signals for the sound exposure

were recorded on digital tapes in advance, and

then played on a TCD-D3 Sony digital analog

tape player (DAT) during the experiment.

The warble tone (240Hz ± 80Hz) was designated tape SI, and the 100 second sweep (230

- 320 Hz) was designated tape SO. The description of the signals is detailed elsewhere

in the report. The output of the DAT was connected to the input of a 5435 Kay Electronics

attenuator, which was used to control the SPL

during sound checks and calibration (Refer to

the schematic of the equipment setup in Figure Al). The output of the attenuator was connected to input (Jl) of the Supplemental FailSafe Cutoff (SFC) circuit. The SFC reduced

the power amplifiers input to zero when the

SPL exceeded a predetermined level. In addition, the SFC would sound an alarm indicating an excessive SPL had occurred. A more

thorough description of the SFC circuit is outlined in the safety section. To detect the SPL

near the diver during the exposures, a H56

monitor hydrophone was installed 61 cm from

the diver at chest level. The output of this

hydrophone was connected to an external preamplifier, which in turn was connected to input (J2) of the SFC.

SIGNAL

SOURCE

ATTENUATOR 1/3 OCT

FILTER

1 POLE

FILTER

AMPLIFIER

PRIMARY oPROJECTOR

HYDROPHONE o

o

DAT

RECORDER

SPECTRUM

ANALYZER

AMPLIFIER

COMPENSATING PROJECTOR

SIGNAL CHAIN FOR TRANSMITTING AND RECEIVING EQUIPMENT

FigureAl. Signal chair for transmitting and receiving equipment

Appendix A-l
The exposure signal from the SFC output

was routed to both the primary and secondary

transducers. The primary route was first connected to the GE 30 1/3 Octave Graphic

Equalizer. The Equalizer was used in the calibration process to compensate for the projector frequency response and flatten the

spectrum. The output of the Equalizer connected to the Instruments Inc. LD1-3 Kilowatt

Amplifier which powered the Jll/3 (primary

transducer). The secondary route was fed to

an SR560 Stanford low pass filter and preamplifier. The low pass filter was used to correct

the drive response of the compensating

transducer by filtering out the frequency components above 300 Hz. The output of the filter was connected to the Kron-Hite 7500

Amplifier which powers the J15/1 (compensating transducer). The role of the compensating

transducer is described in detail in the calibration section.

Sound Receiving Setup

An H56 hydrophone was used to monitor

the SPL at the diver location. The output of

the H56 was connected to three different devices: The first device, a Sony DAT, was

used to record all SPL information while the

divers were at depth. The second device, a

3562A Dynamic Signal Analyzer, was used to

analyze the sound pressure and particle velocity during the calibration procedures and exposure dives. The third device connected to the

output of the H56 was the SFC described

above.

Safety Precautions

NOTE: All sound levels are specified in

decibels referenced to 1 micro Pascal (dB re

1//Pa).

The projectors and amplifiers, described in

the transmitting section above, were configured such that the amplifier outputs were floating with the instrument cases tied to ground.

A schematic of this grounding scheme is

shown in Figure A2. The power cables feeding the projectors were sheathed in copper

KRON-HITE 7500

POWER AMPLIFIER

LD1-3 POWER

AMPLIFIER

COPPER

SHEATHING

J15/ 1 PROJECTOR

FigureA2. Grounding scheme

Jll/3 PROJECTOR

Appendix A-2
screening and then connected to each projector housing . A 10 gage wire was connected

to the housing of the projectors and then

brought to the surface ground. The surface

ground was connected to "earth ground", a

forty foot, four inch diameter steel grounding

rod. The resistance between any ground point

on the test barge and the grounding rod was

less than 1 ohm when certified. The resistance from the signal leads, to the projector

housing, was greater than 20 Megaohms for

both projectors. This was checked on a daily

basis during the testing period.

In addition to the grounding precautions,

the cables of the Jll/3 and J15/1 were also

checked with a megaohm meter daily to prevent excessive levels of leakage current. On

June 30,1995 the resistance's of the Jll/3

and J15/1 cables were measured at IG (500

volts between pairs) and 100 M (100 volts between pairs) respectively. These values were

well above safety levels, but if they fell below

safety levels the projector was replaced and rechecked before continuing the experiment.

To guard against a subject being exposed

to a SPL in excess of 163 dB during the experiment a supplemental Fail-Safe Cutoff

(SFC) circuit was installed between the attenuator output and power amplifiers input. The

H56 hydrophone, which monitored the SPL

near the diver, was connected to the J2 jumper

on the SFC. For normal SPL (less than 163

dB), the SFC is a unity-gain inverting amplifier. An input signal of up to 2 volts RMS

can pass through the SFC with only a 180°

phase inversion. If the signal at J2 exceeds 2

volts RMS, corresponding to a 163 dB or

greater SPL, the signal to the amplifier is cut

off (the signal to the power amplifiers is reduced to zero) and the SFC sounds an alarm.

This condition is latched and can only be

cleared by cycling the SFC power off and

back on.

Calibration ofSound Field

The objective of the calibration was to create a sound field in which a diver can be exposed to the same pressure and impedance

conditions found in open water (the far field),

over the frequency range of 160 to 320 Hz.

To simulate a far field condition in the near

field the pressure wave must act as a plane

progressive wave in the diver test location.

The characteristic property of plane waves is

that each acoustic variable (particle displacement, density, pressure, etc.) has constant amplitude on any given plane perpendicular to

the direction of wave propagation. Therefore,

a re match is achieved when the ratio of total

pressure (pressures from the projector add as

scalars) to total velocity (velocities add as vectors) matches p / v at every point in the test

area. When this match is achieved the result

is a plane progressive wave in the test area

with a specific acoustic impedance (Zac) of:

Zac = p / v = re.

The reactive components present in a near

field condition must be canceled out in

order to attain a re match. The equation

for impedance in the near field can be written:

Zac = rc[R(kr)+jX(kr)]

where R(kr) represents the resistive (or real)

component, and jX(kr) represents the reactive

(or imaginary) component of the impedance.

The k in the (kr) term represents the free field

wavenumber, and r indicates the distance

from the source. To accomplish the impedance match, a Jll/3 transducer (primary projector) is driven at the desired SPL, and a

J15/1 transducer (compensating projector) is

placed symmetrically about the test area and

driven out of phase with the primary

transducer at a significantly lower amplitude.

The amplitude, phase and frequency response

of the two projectors are set such that the imAppendix A-3
Rp(kr) ' X REAL AXIS

- i IMAGINARY AXIS

B

AxF

R{?"\

?

rt

vT

Jk

„^ — —^

/ N

/ N

/ \

/ \

/ \

/ \

1 z \

* 1

\

\

\

1

1

1

\ /

\ /

•v s

Ar

FigureA3. Graphical representation of the

cancellation effect in polar coordinates

pedance match is obtained, and a free field

condition exists in the test area. The procedure for obtaining this free field condition is

outlined in the calibration procedure below.

A graphical representation in polar coordinates of the cancellation affect is shown in

Figure A3. Figure A3a represents the approximate amplitude and phase of the specific

acoustic impedance (Zp) when the primary

projector is operating alone, and A3b represents the specific acoustic impedance (Zc)

when the compensating projector is operating

alone. When the projectors are operating together the resultant impedance (Zac) of the

compensating projector is almost purely reactive, and the amplitude is much lower than

that of the primary projector. In fact, the actual correction amplitude of the compensating

projector was approximately 20 dB lower than

that of the primary projector. Figure A3 does

not represent the actual impedance characteristics, but gives an approximation for illustrative purposes.

Calibration Procedure forAttaining the PC

Match

The particle velocity is the parameter chosen for calibration purposes because the Zac

is the ratio of acoustic pressure (p) to particle

velocity (v) for a plane progressive wave. To

measure the particle velocity a pressure gradient hydrophone is used because pressure gradient is proportional to particle velocity.

Pressure gradient measurements are made at

positions -40, -20,0,20, and 40 cm on the Z

axis as shown in Figure A4, and an H56

hydrophone is used to measure the pressure at

the same locations. Measurements are taken

along the x and y axis to verify the sound

field after the calibration is completed.

First, the band levels on the 1/3 octave filter are varied until a flat pressure response is

achieved at the center point of the test area,

PRIMARY SOURCE

SECONDARY SOURCE

FigureA4. Measurement points in the

diver test area.

Appendix A-4
with only the primary projector being driven.

Second, the compensating projector is turned

on and the high frequency cutoff of the 1 pole

filter is set to approximately 300 Hz. This

value is chosen because the lower frequencies

require more correction than the higher frequencies. This is illustrated in Figure A5

where it shows the pressure gradient correction required at 160 Hz is approximately 2

dB, and at 300 Hz is approximately 0.5 dB.

The third step is to achieve a plane wave condition, a re match. The pressure and the pressure gradient are monitored at the center of

the test area. The amplitude of the compensating amplifier, and the frequency cutoff of the

1-pole filter are fine tuned until the pressure

and the pressure gradient indicate a re match,

while maintaining a SPL of 160 dB between

160 and 320 Hz.

The next step is to move the pressure gradient hydrophone to the 40 cm point on the z

axis and repeat the frequency response measurement. If the difference between the center

spectra and 40 cm point measurement concur

within 2 dB at the frequencies of concern, the -

40 cm point is checked. If it does not, the filter settings, and amplitude of the

compensating amplifier are adjusted until the

criteria are met at the 40 cm point. The center

point is rechecked, and fine adjustments to the

two parameters (SPL and filter cutoff frequency) are again made to meet the criteria.

This procedure is repeated until the variation

from the -40 cm to the 40 cm point is no

greater than ± 2 dB in all directions, while

maintaining the re match and the 160 dB SPL.

Finally, measurements are taken along the x,

y, and z axes to verify that the sound field is

balanced about the center point. The center

point (0) is the diver location (the diver's

chest)

CO

CO

UJ

cc

O- IOO 120 140 160 180 200

FREQUENCY (Hz)

FigureA5. Pressure gradient required for compensation transducer

r

240

T 1 1

260 280 300

Appendix A-5
[Blank Page]

Appendix A-6
APPENDIX B

DIVE PROTOCOL

1. Objective: The purpose of this experiment is to determine the effects on divers of exposure to

underwater active sonar. The basic design consists of exposing divers to underwater sonar at a

level which they may be exposed to during a working dive, and determine their tolerance based

on subjective responses, medical monitoring, and performance tests. In the present experiment,

exposure to a narrow range of low frequencies (pitches) will be tested. The signals used will

simulate an actual active sonar system. Previous experiments in enclosed laboratory

environments suggest that such exposures should be well tolerated. However, differences exist

between open water and closed tank acoustics. This experiment is designed to determine if these

differences significantly affect a diver's tolerance to underwater sound.

2. Medical Examinations: All of the measurements administered during these experiments are

established clinical measures. Divers will be given thorough physical exams including a

complete neurological exam and neuropsychological assessment. These exams may also include

routine blood, urine, and fecal sampling, and a chest x-ray. Additional measures include

electroencephalography (EEG), videooculography, audiometry, spirometry, electrocardiography

(ECG), balance platform testing, dynamic visual acuity testing, a sustained attention test (SAT),

and a symptoms survey. Thorough physicals, audiometry, spirometry, and EEG will be

conducted before and after complete participation in the study. ECG, videooculography,

symptoms survey, and the SAT will be conducted at the dive site (during each dive) before,

during, and after each exposure. Balance platform testing, dynamic visual acuity testing, and

additional audiometry will be conducted at the dive site before and after each dive.

Prior to and immediately after each dive, diver subjects will also be examined by the

Principal Investigator (PI) who is a diving medical officer. The PI or the dive watch medical

officer (DWMO) may order additional measurements after any exposure if a change in the state

of the diver subject is suspected.

3. Watch Section Duties:

Dive Supervisor: A senior diver, E6 or higher, will directly oversee all diving operations.

He will have control over all scheduling and safety of the diver test subjects. The Dive

Supervisor may appoint an alternate qualified Dive Supervisor during his absence.

Principal Investigator (PI): LT Christopher C. Steevens, MC, USNR, Biomedical

Sciences Department, Naval Submarine Medical Research Laboratory has overall responsibility

for the conduct of the experiment. He will schedule all activities with the Dive Supervisor and

the test facility manager. The PI will maintain all experimental logs.

Appendix B-l
Recorder: This function will be performed by a diver-subject under control of the Dive

Supervisor. The Dive Supervisor will maintain dive duty logs as required by standard Navy

practice.

Surface Tender, Communicator, and Standby Diver: These functions will be designated

by the Dive Supervisor. Two-way voice communication will be maintained using a standard

Navy Communication system. The surface tender will also communicate with the subject by line

pull as needed. In addition, the subject will be monitored by a video camera attached to the diver

support structure. The video monitor will be located topside to be viewed by a member of the

crew designated by the Dive Supervisor. The standby diver will be fully suited at all times and

be prepared to enter the water to assist the subject in the event of an emergency.

Medical Monitor: LT Robert Harris, MC, USN, Biomedical Sciences Department, Naval

Submarine Medical Research Laboratory will act as medical monitor. He will consult with the PI

and Dive Supervisor regarding any medical aspects of the dives or the experiment.

4. Subjects: There will be 6 primary subjects and 4 alternates. The subject population will

consist of active-duty US Navy divers, possessing Diver Second Class qualification or higher.

Divers will be medically qualified for diving as determined by a US Navy Diving Medical

Officer. There are no restrictions as to age or sex of the diver.

5. Dive Records and Logs: A dive log will be kept by the Dive Supervisor. Ancillary logs are

not required. Experimental logs including data will be kept by the PI.

6. Compression phase: Compression/Decompression rates are under the control of the diver

subject, his tender, and dive supervisor in accordance with standard practice.

7. Depth Control: Divers will be suspended from a diver support structure which will be

maintained at the desired depth for each dive. While the depth will be fixed for each individual

dive, it will vary between dives. Depths to be used will be 30 and 60 ft.

8. Excursion Procedures: None.

9. Atmosphere Control: Surface supplied compressed air will be used for dives using MK-20

and MK-21 diving rigs. Air diluent will be used for the MK-16 diving rig.

10. Emergency Breathing Gas: None required. However, umbilical gas supply will be used via

the MK-20 FFM for MK-16 dives (waiver required).

11. Contaminated Gases: Standard U.S. Navy Diving Manual Procedures for surface supplied

air, and closed circuit rebreathers will be followed to ensure gas purity.

12. Termination Criteria: Each subject may terminate any dive for any reason. Subjects will be

instructed to terminate any dive if they feel pain or excessive discomfort from noise exposures.

Appendix B-2
The Dive Supervisor, PI, and medical monitor may also terminate any dive. Guidelines for

continued exposure to underwater sound are covered in the main protocol.

13. Abort Procedures: Standard dive surfacing techniques.

14. Decompression Phase: For dives requiring decompression, in water decompression will be

conducted according to U.S. Navy decompression tables. At the Master Diver's preference,

surface decompression using oxygen may be used. Bottom times for all dives will be limited to

40 minutes.

15. Decompression Sickness fDCSV Arterial Gas Embolism (AGE^ Diagnosis and Treatment:

Any casualties will be evaluated by an on-site DMO, and treated at an on-site recompression

chamber and/or local hospital as needed.

Appendix B-3
[Blank Page]

Appendix B-4
APPENDIX C

Spirometry Testing

Spirometry was performed using a hand held portable SpiroSense spirometer. All

subjects underwent baseline testing prior to any experimental diving. The baseline test

used in this study was the Flow/Volume Loop. The Flow/Volume Loop is a Forced Vital

Capacity (FVC) maneuver followed by a maximal inhalation maneuver. The test requires

that the subject fill his lungs maximally, then exhale forcefully as long and as hard as

possible through the spirometer flow sensor, then complete the loop by inhaling

maximally through the flow sensor. Subject understanding and cooperation is necessary

for an acceptable test. A trained pulmonary technician was present to coach the subjects

through each maneuver. In addition, subjects were able to view a real time graph of the

flow loop giving them visual as well as audio incentive. The SpiroSense automatically

determines the end of test, and comments on the quality and reproducibility of each

maneuver. The pulmonary technician and principal investigator reviewed each test for

acceptability. Each subject performed three acceptable maneuvers during baseline

testing.

Following the series of experimental dives, subjects repeated Flow/Volume Loop testing.

Again, each subject performed three acceptable maneuvers. These results were compared

with the results of baseline testing to determine whether a restrictive or obstructive airway

disorder was induced by underwater sound exposures.

Appendix C-l
[Blank Page]

Appendix C-2
APPENDIX D

Neuropsvchological/Neurological Testing Procedures

Neuropsychological Assessment

Test Battery

Group Administered: Cognitive Behavior Rating Scale, Beck Anxiety Inventory,

Beck Depression Inventory and Shipley Scale.

Computer Administered: COGSCREEN and Non-Verbal Selective Reminding.

Individually Administered: Wisconsin Card Sorting, California Verbal Learning (Forms 1

and 2), Continuous Visual Memory (Forms 1 and 2), Paced

Auditory Serial Addition, Reitan Train Making, Symbol-Digit

Modalities, Reitan Finger Tapping, Grooved Pegboard, Grip

Strength, Controlled Oral Word Association and Stroop

Color/Word Interference.

Description

The four-hour pre-dive neuropsychological battery included measures of intelligence

(abstract sequence completion and multiple-choice vocabulary), concept formation,

memory (verbal and visuospatial), reaction time (simple and choice), divided attention,

focused attention, mental flexibility, coding speed, verbal fluency (word-list generation),

manual skills (finger tapping, dexterity and grip strength), mental calculation, digit span,

right-left orientation, visual matching-to-sample, and dual task performance. All

measures were repeated following the dive, except the measures of intelligence and

concept formation. Each subject also rated their current levels of anxiety, depression,

memory impairment and other cognitive difficulties before and after the low-frequency

water-borne sound dives.

Appendix D-l
Neurological Assessment

Pre/Post Study

Comprehensive neurolgic tests to evaluate subjects at study entrance (beginning) and exit (end).

Test: Electroencephalography (EEG)/Brain Electrical Activity Mapping (BEAM)

Test equipment

Bio-Logic ® Brain Analysis System.

Test length

Set up and subject preparation: 20 minutes.

Recording: 20 minutes.

Analysis time: 30 minutes.

Test protocol

Subject's electrocortical brain activity recorded from scalp electrodes using standard

bipolar montage.

Patient is awake and resting, and undergoes brief period (3 minutes) of

hyperventilation.

Test Analysis

Raw EEG electrocortical brain activity reviewed for abnormalities and artifacts.

Digitized electrocortical brain activity analyzed using Fast Fourier Transformation

(FFT) after artifacts deselected.

Data compared pre/post study (within subjects) and compared to population normals

(between subjects).

Data storage

250 MB Tape, Hard drive, printed summary of Spectral Plot, relative and absolute

power.

Pre/Post Study

Comprehensive neurolgic tests to evaluate subjects at study entrance (beginning) and exit (end).

Test: Quantitative Oculomotor Performance Battery

Test equipment

Micromedical Technology ® VORTEQ system.

Neurokinetics ® Contraves rotational chair system.

Test length

Setup and subject preparation: 5 minutes.

Recording: 30 minutes.

Analysis time: 20 minutes.

Appendix D-2
Test protocol

Standard electrooculography (EOG) electrodes applied to subject.

EOG calibration conducted prior to recording.

For the standard test series, the subject is seated and secured in rotational chair.

For the Vestibular Autorotation Tests, the subject wears yaw (side to side) axis

angular rate sensor secured on headband.

Test series

Oculomotor Tests (each test records 30-60 seconds of EOG)..

Spontaneous and Gaze Evoked Nystagmus (1 trial).

Saccade (fast) eye movement (2 trials).

Pursuit (slow) eye movement (3 trials).

Visual Vestibular Interaction Tests (each test records 30-120 sec of EOG)

Optokinetic Nystagmus (OKN) (2 trials)

Vestibular Ocular Reflex (VOR)

Sinusoidal Harmonic Acceleration (5 trials)

Impulse Acceleration (2 trials)

Visual Vestibular Ocular Reflex (VVOR) (1 trial).

Vestibular Ocular Reflex Suppression (Ocular Fixation) (1 trial)

Off Vertical Rotation Nystagmus (OVR) (2 trials)

Tilt Suppression of Post Rotatory Nystagmus (PRN) (2 trials)

Optokinetic After Nystagmus (OKAN) (2 trials)

Vestibular Autorotation Tests (each test records 15 seconds of EOG)

Vestibular Ocular Reflex (VOR) (1 trial)

Visual Vestibular Ocular Reflex (WOR) (1 trial)

Vestibular Ocular Reflex Suppression (Ocular Fixation) (1 trial)

Test analysis

Digitized eye and head position and eye velocity, latency and accuracy scores

analyzed and reviewed for abnormalities.

Gain refers to peak or maximum eye slow phase velocity (SPV) to head SPV.

Gains compared pre/post study (within subjects) and compared to population

normals (between subjects).

Test descriptions

Nystagmus Test

Test description:

Subject sits in dark room with eyes open.

EOG recorded while subject is staring forward (primary position) and 20

degrees left or right (secondary position).

Significance:

1) Nystagmus in primary position is usually vestibular in origin, may be

congenital.

2) Nystagmus in secondary position is gaze evoked, may be vestibular.

Appendix D-3
Saccade (Fast eye movement) Test

Saccade system used to move eye to acquire targets located off the visual axis

(peripheral vision).

Saccade system supplements smooth pursuit, maintaining retinal image stability,

when targets move faster than 100 deg/sec (constant velocity) or 150 deg/sec

(sinusoidal motion).

Test description:

Subject in stationary chair in dark room instructed to track rapidly moving laser

target

Two trials (rhythmic and random)

Target moves rhythmically (0-10 deg) and randomly (0-30 deg) left or right of

center results in fast eye movement that closely matches target position and

velocity.

Significance:

1) Reduced saccade latency may indicate frontal lobe dysfunction

2) Impaired saccade accuracy or velocity indicates brainstem oculomotor

dysfunction

Smooth Pursuit (SP) / Slow eye movements Test

Maintains retinal image stability for slow objects moving at < 100 degrees/sec

Description:

Subject in stationary chair in dark room instructed to track slowly moving laser

target.

Target moves 30 deg left and right of center at 3 test frequencies (0.1,0.2, 0.3

Hz).

Results in slow eye movement that closely matches target movement.

Significance:

1) No pursuit eye movements (only catch-up saccades), indicates cerebellar

dysfunction.

2) Reduced pursuit when target moves toward one side indicates parietal lobe

(cerebral) hemisphere dysfunction (ipsilateral)

3) Reduced pursuit gain in both directions seen with altered mental state

(alcohol, medication, fatigue, or inattention)

Optokinetic Nystagmus (OKN) Test

Eye movements induced by moving 360° visual field surround (retinal slip stimulus)

enables retinal image stability of object of regard while ignoring competing

motion signals results in nystagmus with slow phase in same direction of OKN

stripe rotation.

Test description:

Subject seated in stationary chair (earth vertical axis).

Rotating OKN stripes projected onto wall, then stripes off in darkened room.

OKN visual stimulus:

Projector generated vertical regular black/white stripes

Stripes extend 45 degrees above and below horizon

Stripes project around full visual field (360 degrees horizontally)

Appendix D-4
OKN stripes rotated horizontally at 60 deg/sec

OKN stripes rotated 1 trial clockwise, 1 trial counterclockwise

OKN stripes projected for 60-120 seconds

Significance:

1) Reduced OKN slow phase component indicates ipsilateral parietal lobe

dysfunction

2) Reduced OKN fast phase component indicates contralateral frontal lobe

dysfunction

Vestibular Ocular Reflex Test

Maintains ocular stability during head motion by generating compensatory eye

movement opposite to head movement

Test description:

Subject sits in rotating chair in darkened room

Results in nystagmus with slow phase in opposite direction of movement

stimulus

Gain measured (peak or maximum eye slow phase velocity (SPV) to head SPV)

Stimulus profiles:

1) Sinusoidal Harmonic Acceleration (SHA)

Test Profile: 1-67 cycles at 0.01,0.02, 0.04,0.08, 0.16 Hz at 60 deg/sec

2) Step Velocity

Test Profile: 1 trial clockwise, 1 trial counterclockwise

Rotated 60-120 seconds at 100 deg/sec

Significance:

1) Unilateral vestibular dysfunction

Reduced gain at lower rotation frequencies

Larger phase advance (phase lead) at higher frequencies

2) Bilateral vestibular lesion has lower gain than unilateral lesion

Visual Vestibular Ocular Reflex (WOR) Test

Maintains ocular stability during head motion by generating compensatory eye

movement opposite to head movement, with visual feedback present.

WOR gain is higher (more accurate) than VOR gain.

Test description:

Subject sits in rotating chair (earth vertical) in room

Subject viewing stationary visual stimulus while rotating

Projector generated vertical regular black/white stripes

Stripes extend 45 degrees above and below horizon and 360 degrees around

Results in nystagmus with slow phase in opposite direction of rotation

Stimulus Profile

Sinusoidal Harmonic Acceleration (SHA) for 1-6 cycles at 0.04 Hz at 60

deg/sec

Significance:

Reduced gain at lower rotation frequencies indicates parietal and vestibular

dysfunction

Appendix D-5
Reduced gain at higher frequencies indicates unilateral vestibular dysfunction

Absent gain at higher frequencies indicates bilateral vestibular dysfunction

VOR Suppression (VOR-S) Test

VOR-S is the ability to voluntarily override the VOR to allow ocular tracking of

object moving with head (head fixed target), effective at lower head

oscillations (0.1-1.0 Hz).

Test description:

Subject in rotating chair in dark room instructed to track laser target moving

with chair.

Stimulus Profile:

Sinusoidal Harmonic Acceleration for 1-6 cycles at 0.04 Hz at 60 deg/sec

Chair fixed laser target moves left and right with subject, normally results in no

eye movement as target does not move relative to subject

Significance:

1) Presence of VOR nystagmus (impaired VOR-S) when target moves toward

one side indicates ipsilateral parietal lobe (cerebral) hemisphere dysfunction.

2) Presence of VOR nystagmus (impaired VOR-S) in both directions seen with

altered mental state (alcohol, medication, fatigue, or inattention).

3) VOR-S is similar to smooth pursuit system.

Optokinetic After Nystagmus (OKAN) Test

Test of otolith/semicircular canal interaction (otolith modulation of VOR).

OKAN and PRN are opposite in direction, cancel each other, stabilizing retinal

image.

Test description:

Subject seated in stationary chair (earth vertical axis).

Rotating OKN stripes projected onto wall, then stripes turned off.

Stimulus:

OKN stripe profile: 1 trial clockwise, 1 trial counterclockwise.

OKN stripes projected for 40-60 seconds and rotated at 50 deg/sec.

Once OKN nystagmus reaches peak SPV, OKN stripes extinguished, and

subject keeps eyes open in darkened room.

Significance:

Following sufficient OKN stimulus (40 deg/sec for 40 seconds), OKAN

nystagmus persists after visual stimulus removed (room darkened).

Initial OKAN I: follows OKN, same direction as OKN, then OKAN II, which

follows OKAN I, is in opposite direction of OKN.

Bilateral labyrinth damage, OKN unchanged, OKAN absent permanently.

Unilateral labyrinth damage, OKAN reduced toward affected side.

Vestibular Autorotation Tests (each test records 15 seconds of EOG)

This test sequence uses active (subject generated) horizontal head rotation.

Subject turns head 10-20 degrees right and left at 0.5-4.0 Hz.

Subject wears headband with velocity rate sensor.

Appendix D-6
Vestibular Ocular Reflex (VOR)

Subject in dark room, no visual feed back

Same significance as VOR rotational chair series

Visual Vestibular Ocular Reflex (WOR)

Subject in dark room fixates on earth fixed target light

Same significance as WOR rotational chair series

Vestibular Ocular Reflex Suppression (Ocular Fixation)

Subject in dark room fixates on head fixed target light

Same significance as VOR-S rotational chair series

Data Storage

Hard drive, 3.5 inch disk, 250 Megabyte tape backup, printed summary.

Pre/Post Study

Test: Dynamic Platform Posturography

Test equipment

Neurocom® Pro Balance Master (dynamic posturography).

Polhemus® Head Tracker System.

Labview® data acquisition system.

Audio system with background (pink noise) generator and communication.

Video camera and recorder to view subject.

Test length

Setup and subject preparation: 1-2 minutes.

Recording: 30 minutes.

Analysis time: 10 minutes.

Test protocol

Subject wears safely harness secured to safety bar.

Subject wears pitch - roll axis position sensor secured on head band.

Subject wears headset connected to background noise generator and audio comm

system.

During Sensory Organization Tests (SOT), the subject maintains best balance for 20

seconds of the test condition.

During Dynamic Stability Test, the subject shifts weight to match the designated

indicator, out to a target location at a percentage of the subject's calculated

maximum limit of stability (LOS), based on height and weight.

Sequence of test conditions (22 trials conducted)

(Series One) Standard Sensory Organization Test

Eyes open (EO)/No Head Movements/ Stable Platform (1 trial).

Eyes closed (EC)/No Head Movements/ Stable Platform (1 trial).

Eyes open (EO)/No Head Movements/ Unstable Platform (3 trials).

Eyes closed (EC)/No Head Movements/ Unstable Platform (3 trials).

Appendix D-7
(Series Two) Dynamic Stability Test

Center Target - maintain static position (1 trial).

Rhythmic Weight Shift L/R - target moving left and right to 50% LOS at 3

speeds (1 trial).

Rhythmic Weight Shift F/B - target moving forward and backward to 50% LOS

at 3 speeds (1 trial).

Limit of Stability Shift - shift position from the center to of 8 predictable targets

at 90% LOS and back (1 trial).

Random Limit of Stability Shift - shift position from the center to 1 of 8 random

targets at 90% LOS and back (1 trial).

(Series Three) NAMRL Modified Sensory Organization Test.

Eyes open (EO)/Head Movements/ Stable Platform (3 trials).

Eyes closed (EC)/Head Movements/ Stable Platform (3 trials).

Eyes closed (EC)/Head movements/ Unstable Platform (3 trials).

Test Analysis

Balance and sway path distance scores reviewed for change pre/ post study scores

compared pre/ post study (within subjects) and compared to population normals

(between subjects).

Analyze video tape of instability pattern or fall.

Data Storage

250 MB Tape, Hard drive, printed summary.

VHS tape of subjects during balance test.

Pre/Post Exposure Tests

Rapid screening tests of Neuro-otologic Function administered before and after each LFA

exposure.

Test: Dynamic Visual Acuity Test

Test equipment

Micromedical Technology ® VORTEQ system

Test length

Setup and subject preparation: 1 minute

Recording: 4 minutes

Analysis time: 2 minutes

Test protocol

Subject wears yaw axis angular rate sensor secured on headband.

Subject reads computer generated eye chart at 10 foot distance while turning head

side to side at specific head velocities and frequencies.

Appendix D-8
Computer displays computer generated eye chart when subject turns head at selected

velocity.

Operator encourages best visual acuity from subject.

Five test conditions

static (0 velocity)

0.7 Hz/ 70n deg/ sec

1.0 Hz/100 deg/ sec

1.4 Hz, 140 deg/ sec

2.0 Hz/ 200 deg/ sec

Each test condition takes 20-40 sec to administer.

Test Analysis

Operator scores visual acuity at each test frequency using log Mean Angle

Resolvable (log MAR) scale.

Scores are reviewed for change pre/ post exposure.

Data Storage

Hard drive, 3.5 inch disk, printed summary.

Pre/ Post Exposure Tests

Rapid screening tests of Neuro-otologic Function administered before and after each LFA

exposure.

Test: NAMRL Modified Sensory Organization Test

Test Equipment

Neurocom® Pro Balance Master (dynamic posturography).

Polhemus ® Head Tracker System.

Labview ® data acquisition system.

Audio system with background (pink noise) generator and communication.

Video recorder to view subject.

Test length

Setup and subject preparation: 1-2 minutes.

Recording: 5 minutes.

Analysis time: 1 minute.

Test protocol

Subject wears safety harness secured to safety bar.

Subject wears pitch - roll axis position sensor secured on headband.

Subject wears headset connected to background noise generator and audio comm

system.

Patient maintains best balance.

Appendix D-9
Test conditions

12 trials conducted, each trial measures balance over 20 seconds

NAMRL modified Sensory Organization Test

Eyes open (EO)/ No Head Movements/ Stable Platform (1 trial).

Eyes closed (EC)/ No Head Movements/ Stable Platform (1 trial)

Eyes open (EO)/ Head Movements/ Stable Platform (2 trials)

Eyes closed (EC)/ Head Movements/ Stable Platform (2 trials)

Eyes closed (EC)/ No Head Movements/ Unstable Platform (3 trials)

Eyes closed (EC)/ Head Movements/ Unstable Platform (3 trials)

Test Analysis

Balance scores reviewed for change pre/ post exposure

Scores compared pre/ post study (within subjects) and compared to population

normals (between subjects)

Video tape of instability or fall

Data Storage

250 MB Tape, Hard drive, printed summary

VHS tape of subjects during balance test

Test: Real time in water videooculography (VOG)

Test Equipment

Water proof video camera.

Standard VCR recorder.

ISCAN ® pupillary reflection eye tracking system.

Video Time Based Corrector.

Labview ® data acquisition system.

Test length

Setup and subject preparation: 5 minute.

Recording: during descent, in water exposure, and ascent.

Analysis time: variable, can be real time.

Test protocol

Subject wears waterproof video camera on helmet with adjustable mount.

Operator adjusts power supply to camera and infrared lights to obtain optimal video

signal.

Subject adjusts camera angle and distance with feedback from operator.

Operator adjusts ISCAN unit to obtain centered eye pupil cross hair.

Test analysis

Operator correlates VOG eye movements with audio and full field video.

Appendix D-10
Monitor subject head and eye position, body movement, and visual stimuli.

Operator interprets significance of eye movements.

Eye movement analyzed and reviewed for abnormalities (spontaneous primary

position nystagmus, particularly vertical or torsional nystagmus).

Incident Evaluation

Clinical evaluation to include history and examination with specific focus to

complaints and organ system involvement.

Neuro-otologic Functions Tests (from Pre/Post Study or exposure tests) as indicated.

Appendix D-ll
[Blank Page]

Appendix D-12
APPENDIX E

Procedure for administering audiograms

A GSI16 audiometer with TDH-50 headphones were used to administer all

audiograms performed during the experiment. Figure El shows a block diagram of the

audiometry, and calibration equipment. A B&K type 2636 Measuring Amplifier and a

type 1617 Third Octave filter were used in conjunction with a B&K type 4152 artificial

ear coupler to calibrate the ear phones. The coupler microphone was calibrated with a

B&K type 4220 Piston Phone calibrator and double checked with a B&K type 4230

pocket size calibrator. The audiometry equipment was calibrated on a daily basis before

the morning audiograms were performed. In addition, the audiogram booth was tested to

insure that it met with the ANSI standards for administering clinical audiograms.

SHIELDED CABLES

AUDIOMETER

©

o o

o o o

PC MEASURING

AMPLIFIER

1/3 OCTAVE

FILTER

TEST

HEADPHONES

RESPONSE

BUTTON

XTT7

HEADPHONE

COUPLER

TEST BOOTH

Figure El. Equipment Setup

Each subject had two practice audiograms before receiving five baseline

audiograms over a three day period. The audiograms covered the test frequencies of 250,

500,1000, 2000,4000, and 8000 Hz. During the exposure days the subjects received a

pre-dive audiogram first thing in the morning and a post dive audiogram between one and

three hours after the dive. The audiograms were immediately entered into a spread-sheet

and compared with the subjects baseline. If a shift of lOdB or greater was found at any

one of the test frequencies, the audiogram was repeated and the subjects ears were

Appendix E-l
examined by a medical monitor on site. A post exposure audiogram was administered to

each subject the day after the final exposure.

In addition to the audiograms explained above, each subject received a clinical

audiogram at the Orlando Navy Hospital prior to, and after the experiment. The

audiograms were administered by a certified technician and covered the frequencies of

500,1000, 2000,3000, 4000., and 6000 Hz.

Daily calibration procedure

1. Check the calibration of the equipment by placing the B&K type 4220 Piston

Phone calibrator on the microphone and coupler.

2. Set the 1/3 octave filter to the 1000 Hz band and read the level on the Measuring

amplifier. If the level doesn't read 93dB, adjust the calibration screw until it does. Check

the Measuring amplifier settings if the reading is off by more than 3dB, and repeat the

measurement with the second calibrator.

3. Screw the coupler back together and fit the right earphone snugly into the coupler,

and place the weight bag on top of the earphone.

4. Set the audiometer to 70dBHL, and dial in the first test frequency. Set the filter to

the Band level which concurs with the test frequency and record the SPL in the table.

Compare the level with the previous day's calibration levels. If they are not within ldB

check the earphone placement in the coupler, and verify that all instrument settings are

correct.

5. Repeat this for all the test frequencies in the left and right earphones, and record

the results in the computer.

6. Replace the earphones in the headset and check that the response button is

working correctly.

Appendix E-2
APPENDIX F

SINDBAD sustained attention test (Manual Dexterity Task): A special "key" is used by the

subject in this task. The key is square shaped on one end and round or cylindrically shaped on

the other end. The square and round ends of the key were alternately inserted into matching

shaped target areas on the response panel for 60 sec. The score was the total number of key

insertions. The following instructions were presented to the subject prior to initiating the task:

MANUAL DEXTERITY TASK

THIS IS A TEST TO SEE HOW QUICKLY YOU CAN MANIPULATE A SMALL

OBJECT. PICK UP THE SMALL KEY INSERTION DEVICE DURING THIS TEST. YOU

ARE TO USE ONLY YOUR PREFERRED HAND TO MANIPULATE THIS DEVICE. DO

NOT ASSIST THIS HAND WITH THE OTHER HAND. THROUGHOUT THE TEST, YOU

ARE TO ALTERNATE TWO DIFFERENT RESPONSES: FIRST, INSERT THE ROUND

END OF THE DEVICE INTO THE LIGHTED ROUND CELL MARKED WITH AN

'ASTERISK;' SECOND, INSERT THE SQUARE END OF THE DEVICE INTO THE

LIGHTED SQUARE CELL BESIDE THE ASTERISK. ALTERNATE THESE TWO

RESPONSES AS RAPIDLY AS YOU CAN FOR THE FULL ONE MINUTE OF THE TEST.

A RESPONSE WILL COUNT TOWARD YOUR SCORE ONLY IF THE RESPONSE

DEVICE IS INSERTED ALL OF THE WAY INTO THE PANEL CELL. ALSO, ONLY

ALTERNATED RESPONSES WILL COUNT TOWARD YOUR SCORE: THAT IS,

REPEATED INSERTIONS INTO THE SAME CELL DO NOT COUNT. START

IMMEDIATELY AFTER THE FIVE SECOND COUNTDOWN ON THE TOP NUMBERS.

KEEP WORKING RIGHT UP TO THE END OF THE TEST, MARKED BY NINES SHOWN

ON THESE SAME NUMBERS.

REMEMBER, USE ONLY YOUR PREFERRED HAND AND WORK AS FAST AS

YOU CAN. DO YOU UNDERSTAND WHAT YOU ARE TO DO? READY.

When subject is ready, press a key.

Appendix F-l
[Blank Page]

Appendix F-2
APPENDIX G

Symptoms Survey

While you are in the water, you will be frequently asked the following series of questions.

The intensity of a symptom should be rated on a scale of 0 to 10 as follows:

MODIFIED BORG SCALE

0 5

Nothing at all Severe

0.5 6

Very, Very Slight

1 7

Very Slight Very Severe

2 8

Slight

3 9

Moderate Very, Very Severe

4 10

Somewhat Severe Maximal

1. DO YOU HAVE A SENSATION OF VIBRATION OR NUMBNESS ANYWHERE

ON YOUR BODY? IF SO, WHERE?

2. DO YOU HAVE ANY PAIN?

3. ARE YOU SHORT OF BREATH?

4. DO YOU FEEL VIBRATION IN YOUR CHEST?

5. DO YOUR EARS ACHE OR HURT?

6. DO YOU FEEL WIDE AWAKE AND ALERT?

7. IS YOUR VISION DIM?

8. DO YOU FEEL LIGHTHEADED?

Appendix G-l
9. DO YOU HAVE A HEADACHE?

10. COULD YOU FULLY CONCENTRATE UNDER THESE CONDITIONS?

11. ARE YOU EXPERIENCING ANY OTHER UNUSUAL SENSATIONS?

12. DO YOU FIND THE SOUND ANNOYING?

This survey will be given during each 100 second sound exposure. Questions for which

positive responses were given (or negative responses in the case of questions 6 and 10)

will be repeated with the sound off. Prior to repeating each 100 second sound exposure,

you will also be asked:

13. ARE YOU READY FOR THE NEXT SOUND EXPOSURE?

If you respond "No", the next exposure will be postponed or terminated at your request.

In addition to the above questions, as a diver-subject, you are encouraged to let topside

personnel know of any other sensation or problem you might have. Your participation is

voluntary, and each exposure is performed only with your approval.

Appendix G-2
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APPENDIX I

Neurological Testing: Pre/Post Study Test Results Summary

EEG Brain Electrical Activity Mapping (BEAM) Fast Fourier Transformation (FFT)

Diver Number 5 6 7 8 9 10 11 12

Subject (SyControl (C) S S S S S s c c

Running Memory Task

Spectral Plot 0 0 0 0 0 0 0 0

Relative Power 0 0 0 0 0 0 0 0

Absolute Power 0 0 0 0 0 0 0 0

Resting State

Spectral Plot 0 0 0 0 0 0 0 0

Relative Power + 0 + + 0 0 0 0

Absolute Power 0 0 0 0 0 0 0 0

Test: Dynamic Platform Posturography

Diver Number 5 6 7 8 9 10 11 12

Subject / Control S s s S S s c c

Standard Sensory Organization Test

EO/NoHM/Stable(Sl) 0 0 + 0 - 0 + 0

EC/NoHM/Stable(S2) 0 0 - - 0 0 + 0

EO/NoHM/Unstable(S4) + + + + 0 - + 0

EC/NoHM/Unstable(S5) + + 0 + 0 + + 0

NAMRL Modified Sensory Organization Test

EO/HM/Stable(Nl) + 0 + + + 0 + 0

EC/HM/Stable(N2) + 0 + + 0 + + 0

EC/HM/Unstable(N5) + + + + + + + +

Test: Quantitative Oculomotor Performance Battery

Diver Number 5 6 7 8 9 10 11 12

Subject/Control S S s S s s c c

Saccade Velocity 0 0 + 0 + + + +

Pursuit gain 0 - + 0 0 0 + +

Visual Vestibular Interaction

Optokinetic OKN) gain + + + 0 + + + +

After Nystagmus (OKAN) - 0 + + + 0 + 0

VOR Suppression 0 0 0 - + 0 - 0

Visual VOR (WOR) gain 0 + + + + + + +

Vestibular Reflex (VOR)

Sinusoid + + + + + + + +

Impulse 0 0 0 0 0 0 0 -

Active Head Rotation

Visual VOR (WOR) gain 0 + 0 + - 0 + 0

Trends: - is downward trend from pre to post study

0 is no change from prej to post study

+ is an upward trend from pre to post study

Appendix I -1
[Blank Page]

Appendix 1-2
Appendix J

Neuropsychological Testing

Pre/Post Study Test Results Summary

(scores are means for all subjects.

There were no significant differences between experimental subjects and controls)

MEMORY PERFORMANCE

Variable Pre Post t-value p-value

CVLT

Trial 1 7.4 7.4 0.00 1.000

Trial 5 14.9 15.0 -0.24 .818

Total 62.0 59.7 0.60 .569

Short Delay Recall 13.4 14.6 -1.29 .244

Long Delay Recall 14.3 14.4 -0.18 .864

Recognition 15.9 15.6 1.00 .356

CVMT

Hits 39.8 37.5 2.39 .048

False Alarms 14.3 9.9 3.24 .014

D-Primed 2.3 2.3 -0.03 .977

Total 79.5 81.6 -1.22 .263

Recognition 5.3 4.9 0.81 .442

(Alternate forms used for CVLT and CVMT)

MOTOR + GRAPHOMOTOR PERFORMANCE

Variable Pre Post t-value p-value

Grip Strength

Dominant 61.9 61.0 0.46 .660

Non-Dom 59.4 58.0 1.23 .258

Pegboard

Dominant 66.0 62.0 5.57 *.001

Non-Dom 68.0 62.3 5.24 *.001

Finger Tapping

Dominant 55.3 55.3 0.00 1.000

Non-Dom 48.1 49.9 -1.94 .093

Symbol-Digits

Oral 67.5 73.6 -1.70 .133

Written 55.4 57.0 -1.23 .259

Trail Making

Part A 18.8 18.3 0.34 .741

PartB 47.5 47.1 0.11 .919

* Significant Improvement

Appendix J-l
ATTENTION / CONCENTRATION PERFORMANCE

Variable Pre Post t-välue p-value

Verbal Fluency

Letter C

Letter F

Letter L

Total

16.4 14.8 1.11 .303

14.0 12.9 0.95 .375

13.5 12.5 0.78 .461

42.6 40.1 0.60 .565

7.8 4.0 1.56 .163

12.4 6.5 3.51 *.010

16.1 9.9 3.28 .014

21.8 15.0 3.71 *.008

58.0 35.4 4.32 *.003

2.3 1.8 2.88 .024

2.7 2.2 3.41 .011

104.0 100.6 1.44 .193

73.4 76.9 -1.71 .131

46.3 46.3 0.00 1.000

PASAT

Trl 1 errors

Trl 2 errors

Trl 3 errors

Trl 4 errors

Optime

Avtime

Stroop

Words

Colors

Colors-Words

* Significant Improvement

COGSCREEN Performance

Variable Pre Post t-value p-value

ASCACC

DATIPRE

DATIRTC

DTTAHIT

MATHACC

MTSRTC

SATDACC

SATNRTC

VSCRTC

93.8 97.5 -0.89 .402

6.8 4.8 2.04 .081

293.8 322.5 -2.18 .066

0.5 0.3 0.51 .626

70.0 72.5 -0.20 .844

1315.0 1292.5 0.18 .864

56.5 74.5 -4.57 *.003

680.0 766.3 -0.92 .389

2445.0 2396.3 0.20 .846

Significant Improvement

Appendix J-2
SUBJECTIVE COGNITIVE / EMOTIONAL RATINGS

Variable Pre Post t-value p-value

Beck Scales

Anxiety 2.3 1.1 1.01 .344

Depression 2.6 1.3 2.11 .073

CBRS

Language Deficit 21.4 17.3 4.51 .003*

Apraxia 6.5 6.0 1.32 .227

Disorientation 6.3 5.6 1.00 .351

Agitation 6.6 6.1 0.94 .381

Need for Routine 8.0 7.3 1.43 .197

Depression 30.6 25.4 1.35 .220

Higher Cognitive Deficits 23.0 20.3 2.92 .022

Memory Disorder 29.4 23.5 1.70 .132

Dementia 29.8 26.8 1.83 .109

* Significant Improvement

Appendix J-3
[Blank Page]

Appendix J-4
APPENDIX K

ASSESSMENT OF EYE MOVEMENTS DURING HIGH

INTENSITY UNDERWATER SOUND EXPOSURES IN U.S. NAVY DIVERS

ELIZABETH A. FERREIRA

BRADEN J. McGRATH

JONATHAN B. CLARK

Naval Aerospace Medical Research Laboratory

Naval Air Station

Pensacola, FL

INTRODUCTION

Divers exposed to high-intensity underwater sound have experienced symptoms attributed

to vestibular stimulation. An underwater video occulography (VOG) system was

developed to monitor divers' eye movements, particularly torsion, during exposure to

underwater sonar signals.

MATERLALS &METHODS

Six Navy divers were exposed to 240-320 Hz underwater sound @ 160 dB (re 1 mPa) for

15 minutes daily cumulative exposure for 10 days. Testing was in open water at a depth

of 60 ft. An underwater camera was attached to the divers soft hooded mask or hard

helmet over the diver's right eye. Waterproof power and video cables were attached to

diver's umbilical cable that relayed the video image to a surface control room. Eye

movements were continuously monitored and recorded in a surface control room. A

torsional "calibration" was performed where divers were cued to perform head tilts to be

sure the system was capable of capturing torsional eye movements. Off-site, a NASA

developed torsion analysis system was used on the data.

Torsional Analysis Protocol

1. Pupil edge is detected.

2. Center of the pupil is calculated by determining the center of the pupil shape

detected in step 1.

3. Horizontal and vertical eye movements are measured by recording the pupil

center calculated in step 2.

4 Iris landmarks are selected FROM FEATURES IN THE IRIS.

5: Pattern recognition is used to track the iris landmarks and measure torsional

eye movements.

RESULTS

During each 100 second sound exposure, eye movements were analyzed for

abnormalities while divers looked straight ahead. No spontaneous nystagmus, torsional

or linear, was detected.

Appendix K-l
CONCLUSIONS

This experiment was the first successful attempt to record and analyze eye movements

under water. No sound induced nystagmus, resulting from exposure to 160 dB

underwater sound, was detected in any diver.

Appendix K-2
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Effects oflow-fiequency water-borne soundon divers: Openwatertrial

12. PERSONAL AUTHOR(S)

CC Steevens. R. Sylvester. J. Clark

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1997 October 07

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16. SUPPLEMENTARY NOTATION

17. COSATI CODES

FIELD GROUP SUB-GROUP

18. SUBJECT TERMS (Continue on reverse ifnecessary and identify by block number)

Sound; Underwater; Plane waves; Standing waves; Divers; Safety;

iearing; Vestibular function; Performance; Tolerance

19. ABSTRACT (Continue on reverse if necessary and identify by block number)

Navy divers may be exposed to active sonar transmissions while underwater. Previous manned

experiments to determine safe levels of exposure have all been conducted in enclosed settings characterized by

standing wave sound fields. The purpose of this experiment was to determine if plane wave (open water)

acoustics alters the physiological or subjective responses of exposed divers compared to standing wave

exposures. 54 manned exposures to two low-frequency underwater acoustic signals were performed at depths

of 30 and 60 feet in a fresh water spring. Two projectors were used to create a plane progressive traveling

acoustic wave. Divers were exposed in both helmeted and unhelmeted diving rigs. Effects on hearing,

vestibular function, cardiac rhythm, and a key-insertion task were measured. Subjective responses were also

recorded. In addition, the effects of neoprene wet suits on sound attenuation were measured. Slight

decrements in hearing acuity were detected, but these results were confounded by circumstances unrelated to

the underwater sound exposures, such as ear squeezes from diving, and microphone feedback noise. No

adverse effects in vestibular function, cardiac rhythm, or key insertion performance were detected. Subjective

responses revealed that divers were moderately annoyed by the underwater sound, but overall found the

exposures tolerable. Neoprene wet suits generally act to attenuate low-frequency sound exposures, but under

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certain circumstances may also accentuate a sound exposure, possibly through a resonance effect. There is no

indication from the results of this study that low-frequency water-borne sound exposures in the open water

present any additional risk to divers compared to similar exposures in enclosed environments.

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