Additional Data on Underwater Sound Localization

78TH

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?J11. Re-EntryAcoustical Measurements on a Ballistic Vehicle. GEORGEKACHADOURIAN,General Electric Company, Re-entry U Environmental Systems Division, Philadelphia, Pennsylvania 19101.--Acoustical measurements, with a ported-hole installation, were made at two points on the conical surfaceof a high-performance ballistic vehicle during re-entry flight. The instruments were intended to detect the onset of boundarylayer flow from laminar to turbulent flow. The results of the measurementsare presented with comparison to the findings

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of other standard transition sensinginstruments. In addition, time historiesand spectral analysesof pretransition and transitional acoustic data are presented and discussed.The fundamental design concept of the sensorinstallation is presented and reviewed.

The basic conclusions reached are that

the

ported-hole acoustic-sensorconcept is a feasible one. The usefulnessof the acoustical measurementin boundary-layer technology is that information is acquired that is unobtainable by other meanspresentlyin useand can, with proper application, be a valuable tool in extendingboundary-layer-flow technology.

FRIDAY, 7 NOVEMBER 1969

COTILLION ROOM 1, 2:00 P.M.

Session7K. Nonnormal Speechand Hearing Situations RoY G. KLUMPP, Chairman

Contributed Papers (12 minutes) 2:00

7K1. Method for Analyzing Perceptual Confusions of Consonant Phonemes. THOMAS MURRAY, Communication Sciences Laboratory, University of Florida, Gainesville, Florida 32601.

--A method for analyzing listener's phonemic confusionsof monosyllabicwords was developedin order to determine the type as well as the number of consonanterrors made in certain speech-intelligibility testing situations. This method, which deals exclusively with consonants,allows for the listeners' responsesto be written in phonetics or traditional orthography. Therefore, it can be used with experienced listeners or with naive listeners, which, in some cases, is desired or necessary. From the listeners' responses,the errors are groupedinto simpleconsonant-for-consonant substitutions, substitutions involving consonant clusters, omissions, and additions. The results of the analyses are presented in terms of the percent correct for each phoneme relative to the total possiblenumber of correct phonemesat a certain condition. In this way, the relative intelligibility of eachphonememay be obtained and compared with other phonemesin the same test or with the same phoneme in various testing situations. Preliminary data indicate that the reliability of transforming the orthographicresponsesto phonemesrangesfrom 87% to 93 % Some results of the application of this procedure to the phonemic confusions of divers' speech at various depths and breathing mixtures are presented. 2:15

7K2. Comparative Intelligibility of Monosyllabic Word Lists. R. F. COLF.MAN, Vanderbilt University, Nashville, Tennessee 37204, AND HARRY HOLLIES, University of Florida, Gainesville, Florida 32601.mTwo experiments are reported in which the underwater intelligibility scores of four standard word lists were compared. As would be expected, closed-set lists produced higher scoresthan open-endedtests. Alternate forms of two tests were compared and the results indicated that lists which are equated for difficulty in normal environments were also sufficiently equated for underwater use. A preliminary analysis of phoneme type distortion was derived from one closed-settest, and appeared to demonstrate that, for these experiments, the most common type of phoneme error was in specificationof place of production, with fricative phonemes most affected. 2:30

7K3. Speech Intelligibility of Diving Masks and Mouthcups. HARRY HOLLIEN AND E. THOMASDOHERTY, Communication

SciencesLaboratory, University of Florida, Gainesville, Florida 32601.•In order to speak underwater, SCUBA divers ordinarily must replace their mouthpieces with some sort of muzzle, mask, or helmet. The addition of such cavitites to the vocal tract usually results in distortion to the speechsignal. Accordingly, it was the purposeof this researchto investigate variation in diver/subject speechintelligibility resulting from the use of such devices. Included

in this evaluation

were all

commercially available units plus several prototypes; they

were (a) mouthpieces:double-hoseregulator bit; (b) mouthcups: Bioengionics, Raytheon, U.S. Divers; (c)full face masks: Scott, MDL, Desco; and (d) helmets: Advanced, Kirby-Morgan. All units were evaluated under similar conditions, i.e., with double-hoseregulators and (in most instances) with Aquasonicsmicrophonesplaced in the breathing cavity. Two studieswere carried out. The first in a hyperbaric chamber at the Naval Ship Research and Development Laboratory, Panama City, Florida and the second at NRL Underwater Sound Reference Division, Bugg Spring facility, Leesburg, Florida, and at Rainbow Springs, Dunnellon, Florida. In the first study, diver's speechintelligibility was assessed by standard procedure for five units (bit, Bioengionics, Raytheon, Scott, and MDL) at simulated depths of O, 12, 50, and 100 ft; a small "wet pot" was utilized for the tests. The secondstudy was carried out for all units in 12 ft of water at Bugg and Rainbow Springs. Divers were held in a fixed position and the speech signal was transmitted by "hard line" directly to a tape recorder at the surface. Data show considerable variability among the units evaluated; highest speechintelligibility was found for one of the mouthcups and for the helmets. 2:45

7K4.

Additional

Data

on Underwater

Sound

Localization.

HARRY HOLLIF.•, J. L. LAUF.R, AND PATRICIAPAUL, Communication SciencesLaboratory, University of Florida, Gainesville, Florida 32601.mTheory would predict that humans exhibit little or no ability to localize sounds underwater. In order to test this assumption, three experiments were carried out on diver/subjects positioned in DALS (diver auditory localization system) at a depth of 40 ft in the NRL Underwater Sound Reference Division Bugg Spring facility. In the first two studies, they respondedto four different signals (250, 1000, 6000-Hz sinusoidsand thermal noise) at a sound-pressurelevel

of 110 dB (40 dB re mean underwaterhearingthreshold)transduced by five J-9 projectors 8 ft from the subject's head and at anglesof 0 ø,45ø,90ø, 270ø,and 315ø. In the first experiment, 17 divers, who were free to move their heads, obtained mean The Journal of the Acoustical Society of America

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78TH

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correct scoresof (1) 250 Hz: 50%; (2) 1 kHz: 39%; (3) 6 kHz: 34%; (4) noise:53%; and (5) over all: 44%. In a secondstudy, seven of the subjects replicated this procedure with their headsin a fixedposition;scoreswere almostidentical (over-all mean 41% vs 47%) except for the first (250-Hz) condition; here a drop-off from 61% to 37% was observed.Also, latency of responsewas lessfor the fixed-head procedure. In the third study, sevendiver/subjects were given training in localization by providing them with information concerningthe correctness of their responses (30 trials each) for 25 pps and 1000-Hz signals. Mean improvement on a post-test was noted; in fact scoreswere over 30% better than on the pretest. Implications of these findings with respect to theory are discussed. 3:00

7K5. Intelligibility of Speech Produced in CompressedAir. R. L. SERGEANT,Auditory Research,Naval Submarine Medical Center, Groton, Connecticut06340.--Recordings of three Navy divers reading aloud word lists of the modified rhyme test within an air mixture were made under ambient pressureconditions that varied from 14.7 psia, which is normal atmospheric pressure,to 127 psia, which is roughly equivalent to pressuresfound 250 ft underwater. The recordingswere presented to listening panels consisting of 25-30 sailors each. Analyses were made of the responsesby the panels to sounds in the initial and final positions of test words, and phonemic matrices were constructed. Correct responsesdropped progressively from 95% at 14.7 psia to below 75% at 127 psia. Sounds in the final position of words consistently were less easily recognizedthan those in the intial position, for all pressures studied. Sounds most seriuosly effected by increased pressures,except for/b/, are the lingual dentals/t•, t, d/and /z/, and the least effected sounds,except for/•/are the semivowels/r,1/and/w/. Soundsfor which intelligibility was low under normal pressureconditions of 14.7 psia were either very slightly or not changed at all by increasing pressureto 127 psia. Results of this study can be applied to construction of special vocabularies for use in deep-submergence diving operations. 3:15

7K6. AcousticAnalysis of SpeechProduced in Air Compressed from 14.7 to 147 psia. R. L. SERGEANT,Auditory Research, Naval Submarine Medical Center, Groton, Connecticut06340, ASp J. R. DUFFY, JR., Department of Speech, University of Connecticut, Storrs, Connecticut06268.--Confusions in studies of speech in the deep undersea environment are caused by variations in the response of microphones under abnormal ambient pressuresas well as an interactive effect upon vocal production caused by increases in ambient pressure and changesin gas mixture make up. In the present study, speech was analyzed when the gas mixture, normal air, was held constant, and reciprocity calibrations were made at those pressuresunder study of the microphoneusedin the recordingof speechsamples. Taped recordingswere collectedof the speech of six Navy divers reading listsof wordsand a paragraph inside a pressure chamber at normal atmospheric pressure and at pressuresfound 50, 100, 150, 200, 250, and 300 ft underwater (equivalent to 14.7 to 147 psia). The mean time required to read the paragraph increased 17% from 14.7 to 147 psia. Spectrographicanalysis below 4 kHz showedan upward shift of formant centers of about 175 cycles, regardlessof vowel, formant frequency, or speaker. The effect of a lower limiting frequency of resonancefor the human vocal mechanismis discussedin light of the above results.

?K?. Discrimination of Filtered-Clipped Speech by Sensorineural Hearing-Impaired Subjects. IAN B. TUOMAS AN•) Volume 47

Number 1 (Part 1)

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DAWD W. SPAR}CS, ElectricalEngineeringDepartment,University of Massachusetts,Amherst, Massachusetts01002.•A

form of preprocessed speechknown to be highly intelligible to normal listenerswas heard by a group of subjects with sensorineural hearinglosses.The preprocessing techniqueinvolveshigh-passfiltering (cutoff 1100 Hz, slope12 dB/oct) and infiniteamplitudeclipping.Testswith normallistenersin this laboratoryhave shownthat the resultingspeechhas an intelligibility of 97% under noise-freeconditions and an intelligibility of 90% at a signal-to-noiselevel of 0 dB for PB words after training. Subjects with sensorineuralhearing

losses and averagebilateralSRTs of 65 dB weretestedusing CID W-22 PB word lists. The subjectsheard unmodified speechand then filtered-clippedspeech,both at 15-dB sensation level. Discriminationscoresfor one group of subjects

averaged46% for unmodifiedand 61% for filtered-clipped speech.For the remainingsubjects,presbycusiscases,scores were so variable as to defy analysis. Errors for unmodified

speechwere due mainly to misrecognition of stops,fricatives, and affiricates;errorsfor filtered-clipped speechweremorefrequently due to vowel substitutionsand distortions. •Work supportedby NIH and NASA.-] 3:45

7K8. Discriminationof Formant Transitionsby Listenerswith SensorineuralHearing Losses.J. M. PICICETTAN•) ELLEN S. MARTIN, GallaudetCollege,Washington,D.C. 20002.--Persons with sensorineuralhearing lossesusually exhibit a discrimination deficit for audible speechsounds.Some of the most important features of speech are the transitions in the vowelformant frequencies.How discriminableare these transitions to personswith severesensorineurallosses?We attempted to get a preliminary answer to this question. Synthetic sounds with formant peaks in the spectrumwere employedin discrimination trials. The task of the listener was to hear the occurrence of a formant transition in contrast to no transition.

An adaptive procedure was used to estimate discrimination threshold of frequency transition. The threshold for listeners

with sensorineural impairmentwascomparedwith the threshold for normal listeners.Transition durationsof 50, 100, 300, and 500 msecweretestedin low (0.6-1.2 kHz), middle (1-2 kHz), and high (2-3 kHz) frequencyregions.The resultsindi-

cated that the impairedlistenersneededlargerand longer transitions for threshold discrimination

than did normal lis-

tenersand that this differencewasgreaterat high frequencies than at lower frequencies.[Supportedpartially by U.S. Public Health Service.] 4:00

7K9. Auditory Discriminationof SpeechAltered by a Frequency-Transposition Process. DANIEL L•NG, McGill University,Montreal, Canada,ANt) WmL•AM G. ELY, Zenith Radio

Corporation, Evanston,Illinois 60202.•A single-channel transposing instrument that uses a sample-and-holdprocessto accomplishmultiple transpositionsof input frequencieswas

comparedwith a conventional(linear)amplifier.The purpose of the experimentwas to determinewhether transposition couldimprovethe consonantdiscrimination of 12 profoundly deaf children,aged 8-18 yr. Subjectswere presentedwith a seriesof paired syllablesand asked to indicate by pressing oneof two buttonson a responsedevicewhethereachpair was the same (e.g./se-se/) or different (e.g./te-se/). Consonants were paired to representdifferencesrangingfrom zero to five distinctivefeatures.An equal numberof sameand different pairs,constructedfrom 15 consonants and two vowels/a/and /e/were

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presented under each of three conditions: conven-

tional amplification,transpositionsamplingat 1500 Hz, and transpositionsamplingat 3000 Hz. Analysisof over-all results for pairs judged different showed that discrimination between

1970

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