bluuebunny/crossref_metadata_2025 huggingface dataset:
Coarticulatory effects of vowel quality on velar function
Authors: Bell-Berti F. , Baer T. , Niimi S.
Published: October 2005

The position of the velum for any phonetic segment is determined by at least two factors: the nature of the segment itself and the phonetic environment in which the segment occurs. Given a constant phonetic environment, velar elevation increases, and velopharyngeal port size decreases, through the series of segment types: nasals-open vowels-close vowels-obstruents. It is commonly known that velar elevation for vowels, in English, is affected by adjacent nasals. More general interactions between vowels and consonants both nasal and obstruent, have not been described. Velar elevation was measured for utterances including nasal and obstruent consonants and either close or open vowels. Generally, velar elevation varied as predicted above. In addition, vowel quality was found to affect velar position during adjacent consonants: The velum was lower for both nasals and obstruents in an environment of open vowels than in an environment of close vowels. [This work was supported by NINCDS Grants NS-13617 and NS Fellowship-05332, and NIDR Grant DE-01774.]
Ear advantage in dichotic listening and head size; model considerations
Authors: Lenhardt M. L.
Published: October 2005

The development of ear advantage in children seems to be established by age five. As children mature, binaural accuracy dramatically improves which is presumably due to increased capacity of the speech processor. At age five, the mean head size is 50.5 cm; and at one year it is 45 cm. Two models are postulated to explain dichotic listening are (1) a passive model suggesting that stimuli coming from the right ear arrives at the left hemisphere before information from the left ear and the one ear processing may interfere with the contralateral ear input under some conditions: and (2) an active model suggesting the verbal left hemisphere receives information from the right side of space and spatial localization and selective attention are critical. Two six-year-old females with normal intelligence and head sizes five standard deviations below the mean were given CVs with 0- and 30-ms leg onsets through earphones and loudspeakers. The concepts of processing speed (mylinization) and capacity (dendritic aborization) are discussed in relation to the models in terms of redundancy, accuracy, and errors.
The acoustical conditions preferred for ensemble
Authors: Marshall A. H. , Gottlob D. , Alrutz H.
Published: October 2005

Observations on the acoustical conditions preferred by musicians when performing lead to the following hypotheses: (a) Ease of ensemble depends upon the audibility of musical transients in the early reflection sequence. (b) Reverberation plays only a minor part in ensemble, though it is the most preferred acoustical condition for soloists. These proposals were tested experimentally. Reflection-free recordings of the individual instruments in a string trio were made simultaneous. Each musician then played his/her part again in ensemble with recordings of the other two instruments, while sound fields were synthesized from the recordings to simulate stage conditions. High- and low-pass filtering of the reflections with cutoff frequencies between 250 and 2000 Hz were used in successive trials. The musicians were asked to judge the ease of ensemble relative to the preceding trial. In some cases the musicians volunteered comparisons with earlier trials as well and seemed to find no difficulty in deciding. High-pass reflections were generally preferred to low-pass or even to unfiltered reflections. In subsequent trials the effect of increasing the simulated stage size and of imbalance between reflections of different instruments were included.Some design guides for stages for orchestral music are proposed.
Aspects of the acoustical design and properties of Christchurch (NZ) Town Hall
Authors: Marshall A. Harold
Published: October 2005

The Christchurch Town Hall (2650 seats) is the major hall in a complex which includes a 986 seat theater. It was opened on 30 September 1972 and was designed primarily as a choral symphony hall. Reverberation time (125 Hz–2 Khz) in excess of 2.2 s with the hall full is provided by a volume of 20 500 m3 and reflective surfaces. The basic design aim, audibility of early lateral reflections is achieved by large interior oblique reflectors which hang free from the boundaries of the reverberant volume. The resulting early lateral energy and long RT gives the hall a combination of reverberance, envelopment, and clarity. The paper gives an account of design aims and studies including a ray-tracing computer program with an interactive graphics output. Measurements of T60, T15, integrated early energy and binaural cross correlation have been carried out in the hall. Echograms and other measured data will be presented. Clarity has been measured by a speech intelligibility test with the hall empty except for 40 participants. With T60−2.7 s. at 500 Hz the intelligibility was better than the Peutz criterion for public address systems.
Cost effective evaluation of existing auditoria
Authors: Klepper David L.
Published: October 2005

Many schools, churches, synagogues, and similar institutions are limited in funds for both consultation and remedial work, yet wish to use the opportunity of an auditorium or sanctuary remodeling to improve the acoustical environment for speech and music. We have learned that relatively simple instrumentation, limited to a sound level meter with octave-band analyzer, precision microphone, and calibrator, a multispeed battery-operated tape recorder with charger, and a set of blank and prerecorded test tapes, can permit field measurement, or recording for later analysis, of reverberation time, echoes, sound system coverage and frequency response, the uniformity of sound distribution for a variety of sources, and background noise, with reverberation time analysis requiring playback of recorded tape into a graphic level recorder upon return to the office. Tape recordings of balloon bursts also can permit analysis of early-to-reverberant ratios, if appropriate analysis equipment is available. In addition to balloon bursts, playback of 1/3-octave-band test tapes over house equipment and organ tone clusters are often valuable for reverberation time recordings; while, with care, recordings of actual performances can sometimes yield accurate full-house reverberation time data. Specific projects and unusual conditions are discussed.
An experimental evaluation of the impulse response approach for predictions of transient acoustic pressures
Authors: Fisher G. A. , Lamb W. , Stepanishen P. R.
Published: October 2005

A measurement system has been constructed which combines a computer-controlled positioning carriage and an A/D converter with an effective sampling rate of 100 MHz. This system has been used to investigate the acoustic transient pressure field of biomedical transducers which operate in the megahertz range. Since the pressure at any point in the field can be expressed as the convolution of an impulse response and the acceleration of the radiating surface of the transducer [P. R. Stepanishen, J. Acoust. Soc. Am. 49, 1029–1038, (1971)], a deconvolution is required to verify the impulse response method. A digital computer program for deconvolution which is based on iterative techniques has been developed. Extensive acoustic transient measurements have been obtained via the use of a microprobe hydrophone. A comparison of the theoretical and experimental impulse responses is presented along with a discussion of the results. [Work supported by NIH.]
Resonance scattering of acoustic waves from cylindrical shells
Authors: Murphy J. D. , Breitenbach E. D. , Überall H.
Published: October 2005

The theory of resonance scattering, recently developed for acoustic wave scattering from elastic objects and elastic wave scattering from cavities, is applied to the problem of sound scattering from fluid-filled elastic cylindrical shells in a fluid; in particular, air-filled aluminum shells in water. The eigenvibrations of the shell appear as resonances in the scattering amplitude of each normal mode; these are superimposed on a smooth background which if the shell is made thinner, converts from the amplitude of a rigid to that of a soft cylinder. The resonances themselves are exhibited by subtracting the background from the total amplitude and are seen to become less numerous as the shell gets thinner. This paper is part of a series which investigates the excitation of target resonances in the scattering of acoustic and elastic waves using the theory of nuclear resonances [G. Breit and E. P. Wigner, Phys. Rev. 49, 519 (1936)]. [H. Überall was supported by the Office of Naval Research. Code 421 and E. D. Breitenbach by IR/IED at DTNSRDC.]
Scattering of sound in suspensions of spheroidally shaped particles
Authors: Ahuja A. S.
Published: October 2005

Particles are assumed to have oblate and prolate spheroidal, spherical, disklike, and needlelike shapes. with symmetry axes for oblate and prolate spheroids assumed to be either parallel or perpendicular to the acoustic field. The disk-shaped and needle-shaped particles are assumed to be either broadside or edgewise (or end on) to the acoustic field. Scattering cross section for sound propagation in particle suspensions has been calculated. For large density differences between suspension components. as, for example in clay suspensions, computations indicate substantial effects of particle shape and orientation on the scattering of sound in suspensions. However, for blood, for which the density difference between plasma and red blood cell is about 5%, red cell shape and orientation have negligible influence on the scattering of sound. For all practical purposes, scattering of sound in suspensions follows Rayleigh's law of scattering. [Work supported by NIH.]
A new tool for studying transient thermal effects
Authors: Westervelt Peter J.
Published: October 2005

Recent experiments by L. R. Sulak et al. [J. Acoust. Soc. Am. 61, S580(A) (1977)] demonstrate that an acoustic signal is produced by proton beams deposited in water. If the unmodified theory of the thermoacoustic array were applicable the signal would be expected to vanish at about 4 °C, the temperature for which the static thermal expansion of water vanishes. The signal vanishes at about 5.7 °C [L. R. Sulak et al., Nucl. Instrum. Methods, to be published]. This discrepancy in temperature can be explained by two assumptions which will be justified: In the static case it is assumed that about 10% of the thermal energy resides in Debye-like modes and these modes contribute to the steady-state thermal expansion were the Debye modes to be excited in the transient case they would generate sound by a mechanism equivalent to the parametric array: however, I assume that the Debye modes fail to be excited for short-period processes. Thus the time-dependent thermal expansion is diminished with respect to the static expansion by an amount which shifts the zero expansion to a 2 °C higher temperature. The consequence of this analysis is that the theory of thermoacoustic sources should be modified by subtracting out the parametric source contribution. Experiments should be performed with laser arrays to determine the frequency dependence of the Debye amplitudes. The close connection between thermoacoustic and parametric sources has already been mentioned [P. J. Westervelt, McGraw-Hill Yearbook of Science and Technology (McGraw-Hill, New York, 1977), p. 389]. [This work has been supported by the U.S. Naval Ocean Research and Development Activity.]
Measurement of acoustic boundary fields by real-time optical holographic interferometry
Authors: Clark J. A.
Published: October 2005

A real-time extension of a recently developed optical holographic interferometry method [J. A. Clark, J. Sound Vib. 56(2) (1978)] is reported. In this extension of the basic method, a single hologram of the visualization region in an acoustic test facility is recorded. Then the hologram is developed and reinserted into its original position in the optical system. If the visualization region is illuminated for a short duration while an acoustic wave is propagating through the region, interference fringes can be observed—even directly by eye! —which can be quantitatively interpreted as contours of equal instantaneous pressure. These fringe patterns can also be photographed with a still or motion picture camera. The measurement method is used to investigate scattering of sound at a pressure release boundary such as a free liquid surface or a bubble screen. Motion picture records of the scattering process observed as a function of time, frequency, and source strength will be shown. It is demonstrated for the first time that the instantaneous pressure field can be observed in the region immediately adjacent to a free acoustic boundary. [Research supported by ONR.]
The effects of ultrasound on injection currents in liquid helium above and below the superfluid transition temperature
Authors: Carey R. F. , Rooney J. A. , Smith C. W.
Published: October 2005

Ultrasound produced by PZT4 transducers resonant in the frequency range from 1 to 10 MHz suspended in liquid helium are used to investigate the nonlinear interactions of sound with injection currents produced by a tritium source. Below the lambda point, ultrasound produces a decrease in the observed current. The magnitude of this effect increases with increasing displacement amplitude and decreases with increasing frequency, for a given sound amplitude. In addition, the fractional decrease in current is a constant for a given displacement amplitude and frequency. This constant increases with increasing displacement amplitude and decreases with increasing frequency for a given displacement amplitude. In contrast, above the lambda point ultrasound causes an increase in the magnitude of the observed ion current by as much as a factor of 20 over that of the nonsonated control. The magnitude of this effect depends upon displacement amplitude and frequency. [This work was supported in part by the Air Force Office of Scientific Research.]
The effect of DC polarization on the magnitude and phase of the CM harmonics
Authors: Mountain D. C. , Hubbard A. E. , Geisler C. D.
Published: October 2005

Rectification processes must play an important role in the mechanical to neural transduction process in the auditory system since intracellular recording has demonstrated large DC receptor potentials for sinusoidal acoustic stimuli in inner haircells [I. J. Russell, and P. M. Sellick, Nature 267, 858–860 (1977)]. Any rectification process would not only generate DC potentials but also would generate even harmonic distortion. The magnitude and phase of the CM fundamental and harmonics were measured in scale media of the first turn of the guinea pig cochlea using digital signal-processing techniques. The data suggest that the even order harmonics are the sum of two separate components which are 180° out of phase at low acoustic frequencies. One component dominates at low SPL and the other at high SPL. Positive DC polarization shifts the transition of the two components to lower SPL and a reverse current shifts the transition to higher SPL. The results are consistent with our recent hypothesis that the haircell membrane resistance is nonlinear. [This research was supported by the National Institutes of Health.]
Some comparisons of aircraft noise modeling programs
Authors: Bishop D. E.
Published: October 2005

Predictions of the noise environment due to aircraft noise near airports are needed for a wide variety of planning and regulatory purposes. Several different computer programs, some very elaborate, have been developed to provide these predictions. In application, given the same nominal airport input data, these programs may produce contours that are quite different in size and shape. Differences in modeling algorithms and aircraft noise and profile data are usually responsible for most of these differences. The following factors which should be examined in evaluating aircraft noise programs will be discussed: (1) the basic program structure and modeling assumptions, (2) the algorithms governing the prediction of noise levels for ground-to-ground propagation and transition from air- to-ground to ground-to-ground propagation modes, (3) the stored aircraft noise level and profile data, (4) flexibility in program output formats, (5) program operating complexity and convenience and, (6) overall program operating costs. Examples of contour differences arising from differing modeling assumptions and propagation algorithms will be presented.
Digital Interpolation Beamforming for bandpass signals
Authors: Mucci R. A. , Pridham R. G.
Published: October 2005

Digital time domain beamforming requires that the output of each hydrophone be sampled prior to beamforming at a rate consistent with the Nyquist criterion for waveform reconstruction. If the sample rate is insufficient for direct realization of the required beam delays, then the desired delays can be achieved by digital interpolation at either the input or output of the beamformer; hence the terminology Digital Interpolation Beamforming [R. G. Pridham and R. A. Mucci, “A Novel Approach To Digital Beamforming,” JASA. 63, 425–434 1978)]. The application of digital interpolation beamforming to bandpass signals is developed. First and second order sampling methods are discussed whereby the original waveform can be reconstructed from samples taken at a rate consistent with the bandwidth of the bandpass signal. Beamformer implementations are presented which utilize these sampling techniques and hence, operate on data sampled at the generally low rate dictated by the signal bandwidth. The desired beam delays are realized with the appropriate interpolation corresponding to the sampling procedure. This technique is shown to require less hardware than convention techniques. Efficient methods of digital interpolation via Finite Impulse Response (FIR) digital bandpass and lowpass filters are discussed. The beampatterns which result are discussed for a simple line array.
Nearfield parametric sources of rectangular aperture
Authors: Pridham Roger G.
Published: October 2005

This paper describes a useful nearfield parametric source model for rectangular apertures of large aspect ratio. The model is based on a technique which has been successfully applied to circular apertures by J. C. Lockwood in a companion paper presented in this session. Specifically, the interaction region is subdivided into elemental virtual source apertures which radiate difference frequency energy. The existence of diffraction effects depends on the size and curvature of the virtual aperture and its distance from the field point. When diffraction is important, a field point may reside in the nearfield, cylindrical region, or farfield of an aperture. Lossless correction factors are derived which permit nearfield secondary source level and beampattern predictions to be made using a farfield parametric source model such as that developed by Moffett, Mellen, and Konrad (7th Int. Symp. Nonlin. Acoust. (August 1976), p. 19–21. This relatively simple model permits rapid computation of parametric source performance in the nearfield region. A comparison is given between predictions made using the model and those obtained from an exact numerical solution.
Insufficiency of the target for vowel perception
Authors: Shankweiler D. , Verbrugge R. R. , Studdert-Kennedy M.
Published: October 2005

Quasi-steady-state vowels which attain representative formant frequency values for adult male speakers of General American might be regarded as good approximations to canonical form. Results of experiments on vowel perception do not support this assumption. Two speakers produced tokens of nine different vowels in isolation. Separate listening tests were made by random orders of six tokens of each vowel. A second pair of tests was created by digitizing the speech signals, abstracting a single pitch pulse (at the zero crossings) from each vowel center, and iterating to produce sets of pseudovowels matched in duration to the parent syllables. Listeners' judgments contained nearly twice as many errors for iterated pseudovowels than for the unedited natural versions. A third experiment with OVE-synthesized vowels yielded error rates comparable to those for iterated pseudovowels, not to their natural counterparts. We conclude that natural vowels contain sources of information not captured by target formant frequency values. A fourth study created stylized CVC syllables by adding symmetrical linear formant transitions to the set of OVE-synthesized vowels. Results of listening tests demonstrate a significant gain in vowel identification for OVE CVC vowels in comparison to their ♯V♯ counterparts. These results demonstrate that formant transitions play a major role in vowel perception. [This work was supported by NIH Grant HD01994 to Haskins Laboratories.]
Identification of vowels in speech and nonspeech contexts
Authors: Fowler C. A. , Shankweiler D. P.
Published: October 2005

Strange, Verbrugge, Schankweiler, and Edman [J. Acoust. Soc. Am. 60, 213–224 (1976)] report that vowels are better identified in the context of a CVC than in isolation. The present study investigates the basis for this difference in performance. One basis might be auditory. In contrast to isolated vowels, CVCs are dynamic acoustic events. If the auditory system is more sensitive to dynamic patterns of stimulation than to unchanging signals, the CVC advantage may follow from that. A different account derives from the various proposals that perceivers of speech are sensitive to the acoustic patterning in a speech signal that specifies the vocal tract gestures of the talker. CVCs may better specify their articulatory source than isolated vowels. These alternative classes of explanation are distinguished here by separating the properties of acoustic change and articulatory specification. Three sets of listening tests were devised. The first consisted of nine different isolated vowels presented six times each in random order. The second presented the same nine vowels in a /b-b/ context. The third test consisted of the same nine vowels in the context of formant transitions constructed by mirror imaging the /b/ transitions with respect to the steady-state formants for the vowel. The resulting acoustic patterns include as much acoustic change as the bVb syllables but are not patterns that a vocal tract could produce. Identification of vowels embedded in the mirror-imaged transitions was substantially worse than that of vowels in isolation or in the context of a CVC. We interpret these findings as supportive of an “articulatory” as opposed to an “auditory” account of the CVC advantage. [This work was supported by NIH Grant HD0-1994 Haskins Laboratories.]
Perception of word stress and syllable length
Authors: Smith Mary Regina
Published: October 2005

Listeners were presented with tokens of the nonsense word [lala]. The word contained either two natural syllables of identical length or one natural syllable paired with a longer or shorter syllable made by PCM modification of the natural syllable. In half of the disyllables, the longer syllable was in initial position when the syllables were unequal in length. In the other half, the shorter syllable was first. In one condition, listeners reported the location of word stress. In another condition, they reported which syllable was longer or shorter. Preliminary results indicate that native speakers of American English have a bias to locate stress on the first syllable. However, they will report stress on the second syllable when the longer syllable occupies this position even though they are unable to report which syllable is longer in this case.
On some voicing adjustments of flue organ pipes
Authors: Nolle A. W.
Published: October 2005

An adjustable organ pipe for research is described. The section is rectangular. Micrometer screws control (1) the width of the air jet opening, (2) the height of the edge, and (3) the in-out position of the air jet relative to the edge, all of which are practical voicing parameters. Modular part replacements can change the resonator length, the edge shape, and the shape of the air jet passage and the jet edges. The present survey describes the behavior of open and stopped pipes in the two-dimensional adjustment space defined by (2) and (3) above. Contours are shown for the limits of sustained oscillation, for sound pressure level, for deviation of frequency from the passive resonance value, and for the onset of abnormal modes of operation including reversion to the edge tone frequency, overblowing, multimode oscillation, and exaggeration of anharmonic content.
Practical cycloramic stereotone positioning systems
Authors: Goldsmith David S.
Published: October 2005

Sound pickup systems that allow stereotones about a listener to be suddenly or continuously regrouped, produce chord connection by streamweaving in spatial hearing. Chord connection by such means is fundamentally distinguishable from ordinary progression. While such operation may be attained by switching among microphones in a circular array, overt or mechanical means are preferred, because they present a minimal cue conflict for members of the audience who listen through earphones. The central ensemble conductor's platform containing a servocontrolled 360° perspective microphone formation beneath poses a complex set of design requirements encompassing structural, acoustical, and servomechanical considerations, among others. Such plastic music and designing its means will be discussed, and an economically accessible specimen will be shown.
Vowel space normalization in synthetic stimuli
Authors: Nearey T. M.
Published: October 2005

A “continuum” of 220 two-formant synthetic test vowels was designed with F1 ranging from 220 to 1080 Hz and F2 from 685 to 3515 Hz. These stimuli were presented (using a Glace-Holmes synthesizer) to five phonetically trained listeners in two distinct synthetic vowel contexts. Both context vowels were judged to be acceptable versions of the vowel /i/; however, one of the context vowels had formant frequencies appropriate for (adult) males' speech (F1= 250 Hz, F2 = 2400 Hz) and the other had value appropriate for children's (F1 = 370 Hz, F2 = 3515 Hz). Analysis of the listeners' categorization of the test vowels indicates a systematic upward shift for all their vowel category boundaries (in both F1 and F2) as the context vowel is changed from the “male's” /i/ to the “child's” /i/. Statistically significant shifts are found even for the (a-ɔ/ boundary which is phonetically (and physically) remote from the context vowels. The categorization results are in accord with natural data, since the formant frequencies of all vowels are higher for children than for males. [Work supported by University of Connecticut Research Foundation.]
Perceptual segmentation of consonant-vowel syllables
Authors: Soli Sigfrid D.
Published: October 2005

The segmentation of natural stop consonant-vowel syllables into separable perceptual units was examined. Response times from separate baseline tasks requiring discrimination of syllable pairs differing in place of articulation, voicing, and vowel identity were compared with response times from several selective attention tasks. The same discriminations were made in the selective attention tasks, although other competing stimulus differences were present and had to be ignored. Increased response times over baseline values are predicted when listeners attempt to segregate relevant and nonrelevant discrimination cues which are not separable. No increased response times are anticipated when competing cues can be segregated and separately attended. Results showed increased response times in selective attention tasks when place and vowel cues competed, but not when voicing and place cues or voicing and vowel cues competed, suggesting that for CV syllables the place of articulation and vowel cues, which are interdependent and coincident in syllable formant transitions, form single nonseparable perceptual segments. However, voicing cues appear to be separable from these transition cues. Implications for perceptual processing of acoustic and phonetic units are considered. [Supported by NIMH and NICHD.]
Low-frequency sound attenuation in the Labrador Sea-Baffin Bay region
Authors: Friedel F. C. , Martin R. L. , Browning D. G.
Published: October 2005

A series of long range propagation runs were analyzed to determine attenuation coefficients for the frequency range 25–1000 Hz. Above 200 Hz, the dominant cause of attenuation was boron absorption; below 200 Hz, the attenuation was independent of frequency indicating a scattering mechanism as the cause. In the Labrador Basin, absorption was close to that predicted by the Thorp formula; in the Davis Strait and Baffin Bay, it was significantly higher (1.3–1.5 Thorp). This increase, corresponding to higher pH values, can be attributed to two possible causes, the influence of the oxygen-rich Labrador current and the higher pH values encountered as the sound channel axis shallows. The frequency independent component was similar in the Labrador Sea and Davis Strait but lower in Baffin Bay confirming results reported earlier [R. H. Mellen et al., J. Acoust. Soc. Am. 57, 1201–1202(L) (1975)] and suggesting less scattering in Baffin Bay. (Work supported by NUSC)
Medium range low-frequency signal fluctuations
Authors: Novick A. W. , Shade R. A.
Published: October 2005

Propagation fluctuations have been observed at low acoustic frequencies which vary at rates that far exceed those predicted by simple Lloyd mirror effects. A detailed analysis has been performed for a representative deep water site and the probable cause identified. The source is multipath interaction between the principal propagation mode and the modes just below it in energy. The fluctuation distribution is well fit by a Rician curve and a quantitative comparison between calculated and measured data show excellent agreement. This result is significant in that it implies that (1) the temporal fluctuations observed in the ocean may be related to platform motion and (2) these spatial fluctuations can be modified through array design, possibly resulting in improved signal detection statistics.
Cochlear nerve fiber activity after short-term noise exposure
Authors: Markuszka J.
Published: October 2005

Two chinchillas were studied to determine the critical exposure duration for temporary asymptotic threshold shift (ATS) to occur in single units after exposure to an octave band of noise centered at 0.5 kHz at 95 dB SPL. The same acoustic system was used to expose the ear and record nerve activity immediately after cessation of the noise. Chin 543 was exposed for 2 h, and the pattern of TTS was similar to that found after a 12-h free-field exposure [J. Markuszka, ASA paper (1978)]. TTS of 70 dB or greater occurred for units below 4.5 kHz. Above this point, the amount of TTS steadily decreased to normal levels at 7 kHz. Chin 545 was treated differently. First, 45 normal units were studied to provide a baseline for further comparisons. Then the animal was exposed for 1 h at 85 dB SPL. Units below 1 kHz had TTS's of 25–30 dB. TTS declined to zero at 3 kHz and above. A second exposure at 95 dB SPL for 0.5 h produced startling results. Units near 3.5 kHz were shifted 60–75 dB; the TTS decreasing at lower frequencies. An additional 7-dB increase in TTS was found at 0.5 kHz. A comparison of the two exposures revealed that the first exposure had a decreasing effect on units above 1.3 kHz, and the second exposure had an increasing effect. [Supported by NS 03856.]
Glutamate stimulates cochlear afferent nerve fibers
Authors: Bobbin R. P. , Thompson M. H.
Published: October 2005

It was previously reported that several substances, including glutamate, decreased the magnitude of the compound action potential of the cochlear nerve. [R. P. Bobbin, J. Acoust. Soc. Am. 60, S79 (A) (1976)]. This effect could mean the substances induced asynchronous firing in the cochlear nerve. To test this hypothesis, the bony wall over the scala tympani of the basal turn was removed from guinea pig cochleas and small holes made in Rosenthal's canal from which spontaneous, single-unit activity was recorded with 3M KCl micro-electrodes. Addition of glutamate (50 mM) at a rate of 2μ L/min for approximately 5 min to the opening in the scala tympani significantly increased the spontaneous firing rate of the single units; both aspartate (50 mM) and Ringer's were less active. This activity of glutamate may be taken as further evidence that glutamate may be the afferent transmitter substance. [Supported in part by NIH (USPHS, Grant NS-11647) and The Kresge Foundation.]
The pattern of permanent threshold shift (PTS) after low-frequency noise exposure: A single-unit analysis
Authors: Markuszka J.
Published: October 2005

Four chinchillas were exposed for 9, 14, or 18 days to a 0.5-kHz octave band of noise at 95 dB SPL and allowed to recover for 1, 7, 14, or 28 days prior to acute electrophysiological recording. Single-unit data indicated that the pattern of threshold shift closely matched the pattern of hair-cell loss. A 22-dB PTS was associated with a 35% OHC loss in the apex. Lesions of the basal organ of Corti were identified by loss of responsive units, and areas of large OHC loss revealed units with up to 50 dB PTS. In all animals, a “notch” in the distribution of thresholds occurred in the region of 4 kHz. FTC's of units with CF's above the notch were usually normal and their tails are believed responsible for the failure of behavioral measurements to detect their presence or correctly estimate the magnitude of PTS and cochlear damage [W. W. Clark and B. A. Bohne, ARO paper (1977)]. Recovery was complete or nearly so after 36 h for 9-day exposures, and within 48 h for 18-day exposures. The pattern of cochlear damage was consistent with earlier reports [M. P. Fried, et al., Trans. Am. Acad. Ophthal. Otolaryngol. 82, 285–298 (1976); B. A. Bohne, Ann. Otol. Rhinol. Laryngol. 85, 711–724 (1976)]. [Supported by NS 03856].
Noise survey of the Metro Rapid Rail Transit System; January 1978
Authors: McCord Dickman Donna , Gorski Edward P.
Published: October 2005

The staff of the Metropolitan Washington Council of Governments' Areawide Environmental Noise Program underlook a noise survey of the Washington D.C. Metro Rapid Rail Transit System during the latter part of 1977. The survey included interior, station, and track-side sound level measurements. The staff initiated the Metro noise survey after receiving numerous inquiries, regarding the availability of noise data obtained, since the system has become operative. The survey was conducted using a GenRad Type 1565-B Sound Level Meter. The meter was calibrated before and after each measurement. Every precaution was taken to insure that all of the measurements were obtained under similar conditions. Procedures developed for the Federal Highway Administration were used to analyze the data. These procedures allow the L10 and Leq levels to be determined with 95% confidence. The results of this survey indicate that the Washington Metropolitan Area Transit Authority's efforts to minimize the noise impact from the Metro have been generally successful. In the presentation, the staff will discuss both measurement results and noise control procedures incorporated into the system.
Measurement of acoustic impedance in an enclosure using a resonance method
Authors: Miller R. J. , Mehl J. B.
Published: October 2005

Acoustic impedances are determined using a resonance method. Rectangular enclosures with a maximum length of ca. 0.5 m were constructed of aluminum. The dimensions were chosen to maximize the average spacing of resonances in the range 300–2100 Hz. A resistance-loaded source is coupled to an enclosure at one corner; a microphone is mounted at another corner. A calculator-based automatic data acquisition system is used to measure the in-phase and quadrature pressure signals as a function of frequency. The results are fitted to a complex function for a Lorentzian resonance with sloping background of both phases. The fits yield values of the center frequency f0 and width γ for each resonance. The acoustic impedance of a sample is calculated from the shifts of f0 and γ which accompany complete or partial replacement of a wall by the sample. Various materials were tested. Results as functions of frequency, angle of incidence, and sample size will be presented. [Research supported by University of Delaware Research Foundation and Specialty Composites. Inc.]
Effects of duration on annoyance due to aircraft flyover noise
Authors: McCurdy David A. , Powell Clemans A.
Published: October 2005

A laboratory experiment was conducted to determine the effects of duration on human annoyance to aircraft flyover noise. The experiment was unique in that the duration, Doppler shift, and spectral parameters were individually controlled by specifying aircraft operational factors, such as velocity, altitude, and spectral content, in a computer synthesis of the aircraft noise stimuli. This control prevented the confounding of the effects of duration with other factors in the experimental design such as velocity, spectra, and sound pressure level. In the experiment, 48 test subjects rated the annoyance of a set of noise stimuli which were comprised of factorial combinations of three durations, three velocities, three sound pressure levels and two spectra. Each of the main factors except velocity were found to significantly affect the judged annoyance. The interactions of duration with sound pressure level and of spectra with sound pressure level were also found to be significant. Effects of aircraft velocity and Doppler shift were found only in those flyovers which contained strong tonal components. The effective change in annoyance with duration was found to be very near the 3 dB/doubling of duration predicted by the equivalent energy hypothesis.
Horizontal refraction modeling of warm and cold core eddies
Authors: Scully-Power P. , Nysen P.
Published: October 2005

A two-dimensional horizontal cut has been taken through a cylindrical (beer can) model eddy which has a 30 ms−1 sound-speed contrast from the surrounding ocean. Acoustic propagation through the warm core eddy exhibits multipath effects from near-tangential rays which have an azimuthal deviation of up to 11.5°. In the cold core case, focusing of the near-tangential rays produces a caustic and corresponding shadow zone on each side of the eddy. [Work supported by NUSC.]
Use of eddy modeling in studying acoustically-relevant effects and underwater-sound transmissions
Authors: Henrick R. F. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Mesoscale eddies give rise to large sound-speed variations and large rotational currents, both of which may have considerable impact on underwater sound transmissions. Before transmission through an observed eddy can be adequately studied, a reasonable description of these environmental effects must be available. The primary intent of this paper is to show that, for certain classes of eddies, using limited temperature or current data and an analytical eddy model, approximations to the acoustically-relevant environmental effects can be obtained throughout the eddy. Questions of unique specification of model parameters and of data sufficiency are analyzed. Using a previously-derived eddy model, we present a number of examples including the use of time-independent bathythermograph data and time-dependent data obtained from oceanographic moorings. If the data is sufficient in both type and amount, accurate approximations to sound-speed and current structures can be obtained. However, even if measurements are insufficient for model parameter specification, substantial information can be obtained. Acoustic transmission through the observed eddy can then be studied. Discussion of this problem will be presented as time permits. [Work supported by ONR]
Propagation through a GulfStream Ring
Authors: Weinberg N. L. , Clark J. G. , Zabalgogeazcoa X.
Published: October 2005

Previously reported ray tracing studies of fixed source and receiver propagation through a Gulf Stream Ring have been extended to several new geometries involving receivers below the SOFAR axis and sources at various ranges and depths. Particular attention is given to the variability of multipath structure as a function of source position. Results from an approximate model of horizontal refraction are also presented.
Numerical propagation through an eddy including third-dimensional effects
Authors: Baer Ralph N.
Published: October 2005

A split-step parabolic-equation computer program has previously been used to propagate through a two-dimensional (azimuthally invariant) analytic representation of the sound-speed structure of an eddy [Ralph N. Baer, J. Acoust. Soc. Am. 62, S29(A) (1977)]. A three-dimensional analog of this program has now been utilized to study sound transmission through eddy sound-speed structures which vary azimuthally with respect to the sound source. Variations of the acoustic field with position, both in and out of the plane, will be discussed and illustrated.
Internal friction, modulus defect, and harmonic generation in high-amplitude vibration
Authors: Beshers D. N.
Published: October 2005

At vibrational strain amplitudes in the range 10−4 to 10−3, many metals and alloys exhibit rapid increases in internal friction and modulus defect. For brass and iron these increases have been shown to coincide with the first appearance of slip bands on the external surface. Very strong harmonic generation sets in at the same time, with the second harmonic rising sharply above a square-law extrapolation. We have made quantitative studies of the spectrum as a function of amplitude up to the fifth harmonic, although higher orders are quite visible. The variation is complex. Some progress has been made in duplicating these spectra using computer modeling with a Fourier analysis of dislocation velocity as a function of stress. By combining mechanical and microscopic data, deductions can be made about the dynamics of the sources, at least in some instances.
The use of high power ultrasonics (macrosonics) in studying internal friction and fatigue in metals
Authors: Mason Warren P.
Published: October 2005

High Power Ultrasonics has been a useful tool in studying fatigue and internal friction in metals since a large number of cycles can be obtained in a short time. It was first used by the speaker at Bell Laboratories in 1956. Further work was done at Columbia using an improved arrangement. Brass, copper, iron and titanium were studied. The first three fatigued plastically, whereas titanium fatigued elastically by slipless cracks. A correlation between internal friction and breakaway of dislocations and with two stages of plastic deformation has been found. Optical and electron microscope pictures show the various mechanisms up to the fatigue region. Electron microscope pictures show that fatigue cracks progress much faster for ultrasonic vibrations than for the slower fatigue tests. While the structure changes are somewhat different for ultrasonic vibrations than for low frequency testing, the number of cycles to fatigue is slightly larger for ultrasonic testing than for low frequency testing except for steel.
Use of ultrasound in the prediction of fatigue life
Authors: Lamerand R. K. , Salama K.
Published: October 2005

The effects of strain range on the ultrasonic fatigue lifetime have been investigated in brass and aluminum. The fatigue of resonant dumbell specimens was carried out by means of a piezoelectrically driven exponential horn vibrating at a frequency of 20 kHz, and a displacement amplitude ranging between 10−4 and 10−6 meters. These specimens consisted of a gauge length with an arc of circular profile, flanked by a constant cross-sectional area shoulder. The stress distribution along the gauge length was calculated by considering a hyperbolic cosine function to represent the arc of the circle. Four different sized specimens were used such that the calculated stresses predict their failure to occur over a range between 104 and 109 cycles. All the fatigue tests were performed at a controlled temperature of 0 °C. The results obtained experimentally showed that the number of cycles to failure reasonably agree with Manson's fatigue life predictions in the elastic strain range. This seems to indicate that low-frequency fatigue life in brass and aluminum can be predicted from ultrasonic fatigue tests.
Some acoustic properties of the human pinna
Authors: Kuhn George F.
Published: October 2005

The vertical directivity in the median plane, the radiation impedance, and the pressure-amplitude and -phase distribution in the concha were measured for six different pinnae, molded from the ears of live subjects. The vertical directivity of the external ear above approximately 5.0 kHz results from higher-order acoustic modes excited in the pinna. These modes rotate in the pinna as a function of source elevation (and frequency). Directional nulls are formed, for example, when the driving pressure across the ear-canal entrance has the form of a dipole or the pressure distribution of the analogous (1,0) circular duct mode which is “cut off” in the ear canal. Directional peaks are formed when the driving pressure across the ear-canal entrance is fairly uniform in amplitude and phase, resulting in the (propagating) plane wave mode in the ear canal. The standing wave ratios of these transverse modes in the pinna at 6.0 kHz are as large as 35 dB. The radiation impedance, defined here as the ratio of the acoustic pressure to the volume velocity at the ear-canal entrance, is monotonic with frequency until higher-order modes are strongly excited in the pinna causing “jumps” in the radiation resistance and reactance.
Infrasound Detection and Ultralow Frequency Discrimination in the Homing Pigeon (Columba livia).
Authors: Quine D. B.
Published: October 2005

Auditory thresholds and frequency discrimination thresholds at frequencies from 0.05 to 200 Hz were measured using a cardiac conditioning technique. Auditory thresholds are sufficient for the homing pigeon to detect a variety of manmade and natural infrasounds. Frequency discrimination is sufficient at 2 Hz and above to permit the flying bird to localize sources of infrasound using the Doppler shift produced by his own flight speed. The frequency discrimination thresholds at 5 Hz and above agree well with earlier studies in the kHz range. This unusual sensitivity may be one of the sensory mechanisms used in long distance orientation by the homing pigeon. Research in progress is testing these possibilities in the field. [Work supported by NSF and Cornell Fellowship.]
Human frequency following response to synthetic vowels
Authors: Greenberg S. , Smith J. C. , Marsh J. T. , Brown W. S.
Published: October 2005

Farfield recording of the frequency following response (FFR) to digitally synthesized vowels was undertaken in an effort to determine the role played by periodicity-based auditory mechanisms in the perception of speech. Stimuli consisted of five-formant vocoids with formant patterns corresponding to the vowels [ɪ], [ae], [a], [ɔ], and [U]. Stimulus duration was 48 ms and the rise/decay time corresponded to one (digitally simulated) glottal pulse. Two sets of vocoids were presented, one with a fundamental frequency appropriate to a male voice (125 Hz), the other with an F0 of a female voice (250 Hz). Spectral analysis of the signal-averaged FFR indicated that the largest component of the neural signal corresponds to the fundamental frequency of the stimulus. For certain vowels, local maxima in the FFR spectrum coincide with spectral peaks in the acoustic signal, particularly when the first formant lies below 500 Hz.