bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward a trading relationship between the peak level and the number of long duration impact noises
Authors: Trémolières Claude , Hétu Raymond
Published: October 2005

The purpose of this study was to further investigate the likelihood of models based on a critical level [H. McRobert and W. D. Ward, J. Acoust. Soc. Am. 53, 1297-1000 (1973)] or an equal energy assumption for predicting TTS from impact noises. A group of 15 normal hearing subjects was exposed to series of impact noises of 210 ms e duration presented at a rate of 0.5 s. TTS3 was measured at 4, 6, and 8 kHz following five experimental conditions: (a) determination of individual critical levels (CL) producing a 15 dB-TTS following successive series of 60 impacts. (b) confirmation of CL with a single series of 60 impacts. (c) 1000 impacts at CL minus 12 dB. (d) determination of individual critical numbers (CN) with a uniform peak level of 125 dB SPL. (e) CN/4 impacts at 131 dB SPL. The amounts of TTS were larger following condition (c) than with condition (b) and, similarly, condition (d) produced more TTS than condition (e). Results clearly showed that the effect of the number of impacts is far more important than predicted both by the critical level and the equal energy assumptions. It confirms that impact noises must not be treated as nonreverberant impulse noises.
Frequency selectivity after noise exposure
Authors: Feth L. L. , Oesterle E. C. , Kidd G.
Published: October 2005

In preliminary work, we have measured psychophysical tuning curves before and after exposing normal listeners to noise. The postexposure tuning curves are generally broader than the pre-exposure curves; further, the broadening of the postexposure tuning curves is evident for noise exposures that produce very little (less than 3 dB), or no temporary threshold shift (TTS). While recovery from TTS often proceeds linearly in log time, the broadening of postexposure tuning curves remains unchanged for an extended time. These results lead us to expect that frequency selectivity measures may be more sensitive indicators of the deleterious effects of noise exposure than TTS, and that the temporary effects of noise exposure may be more long lasting than temporary pure tone threshold shifts have indicated. [Work supported by NIH.]
Permanent changes in psychophysical tuning curves following exposure to weak, steep-sided noise
Authors: McFadden D. , Pasanen E. G.
Published: October 2005

Two of three listeners participating in an experiment involving the use of a high-pass noise with a very steep skirt (about −400 dB/octave below about 3000 Hz) now yield forward-masking tuning curves that are considerably less steep on the high-frequency side than was true prior to exposure to the steep-sided noise. The exposures were monaural and intermittent both within daily sessions and across an eight-week period, the “multiplied” noise was weak (spectral level 35 dB SPL, overall level 65 dB SPL), and there is no evidence of threshold shift (PTS). The greatest detuning occurs in the ipsilateral ear at a signal frequency of 2400 Hz, and there is little or no effect at 1700 Hz. There are also contralateral effects, but the patterns are different—the primary change is an elevation in the master level necessary when the masker and signal are the same frequency. There was some initial recovery, but deficits persist three months after the last exposure. These preliminary results indicate that noises with steep skirts should be treated with caution until their damage potential is better understood. [Work supported by NINCDS.]
Noise-induced shifts in males and females for a battery of hearing tests
Authors: Bienvenue G. R. , Scott L. J. , Michael P. L. , Kennedy E.
Published: October 2005

Sex-related differences in the effects of noise on humans have been reported in several areas including physiological reactions, sleep disturbance, and permanent hearing threshold shift. It has been suggested that economic, social, and cultural factors may combine to reduce the opportunity for women to be exposed to high-level occupational and recreational noises. However, this contaminant is absent from research into noise-induced temporary threshold shift (TTS), because the noise exposures are carefully controlled in the laboratory performance of TTS studies. Most research into sex-related differences in temporary, auditory noise-exposure effects have been limited to the examination of threshold phenomena only. In the present study, a variety of noise-induced hearing changes have been examined. Subjects were tested before and after a one-half hour noise exposure using an audiometric test battery that included measures of pure-tone threshold, loudness discrimination, tone-on-tone masking, and loudness and pitch measuring of tinnitus. Data were examined for sex-related differences in the magnitude and incidence of noise-induced shifts in these auditory tasks. Implications of these findings for hearing conservation and for modeling noise effects are discussed.
Vertigo in response to sound stimulation
Authors: McLaughlin N. A.
Published: October 2005

Under controlled test conditions, a nystagmus reaction to loud sound stimulation has been demonstrated to be a normal phenomenon; vertigo, nausea, and cold sweat were found to be possible reactions to loud sound. [N. A. McLaughlin, J. Acoust. Soc. Am. 64, S144(A) (1978)]. The present study investigated whether there was an auditory and/or vestibular “profile” characteristic of the individual who is at risk for a vertiginous reaction to sound stimulation. Subjects who experienced a vertiginous reaction to sound had been stimulated with pure tones of 500, 750, 1000, 1500, 2000, 3000, 4000, and 6000 Hz presented in random order. The results showed that the only physical finding common to all of these individuals was a normal vestibular system and neither hearing acuity nor degree of nystagmus reaction to sound stimulation was a factor. The data indicated a relationship between virtiginous reaction and the frequency of the sound stimuli. 65.8% of the vertiginous reactions resulted from stimulation by pure tones of 500, 750, and 1000 Hz. Order of presentation was not a factor. Diagnostic, physiologic, and environmental considerations are discussed.
The subjective influence produced by white noise
Authors: Martinez R.
Published: October 2005

The effects on people of noise produced indoors is assessed. The annoyance produced by white noise is evaluated here, exclusively as a psychological aspect. The annoyance is defined as a function of perceived noise level (Noys) plus exposition time plus psychological and sociological factors. Statistical procedures were used in the designing of experiments. such as Latin squares. Eighty persons were used as subjects in this evaluation and seven kitchen machines were used as noise sources plus one white noise generator, giving a total of eight sources.
Detection of tones masked by repeatable samples of noise
Authors: Frank Alan
Published: October 2005

Previous studies of the detection of pure tones in repeatable noise have discussed the correlation between performance and the power in the stimulus around the signal frequency under monaural listening conditions. [A. Ahumuda, Jr., R. Marken, and A. Sandusky, J. Acoust. Soc. Am. 57, 385–390 0975)]. The present study discusses the detectability of a 500-Hz tone masked by repeatable samples of noise under both diotic and dichotic listening conditions. Psychometric functions were obtained using a single-interval, yes-no task, for various phase relationships between the tone and each of the several samples of noise. The ability of current models of detection to fit the data will be discussed. For example, the ability of an energy detector to predict the diotic signal threshold will be examined by computing the energy in each stimulus, passing through a filter centered on the signal frequency. The results from dichotic listening conditions will allow us to distinguish between the Equalization and Cancellation model and interaural difference models of detection. [Work supported by NSF research grant BNS-77-17308.]
Backward masking of monaural signals by changes in interaural noise correlation
Authors: Pastore Richard E. , Harris Laura B. , Friedman Carol J.
Published: October 2005

Research from our laboratory has shown that instability or changes in masking noise which are temporally contiguous with the potential signal will result in nonsimultaneous masking effects. The present experiment involves a monaural signal (1000 Hz) embedded in a broadband noise. Noise in the other earphone either was continuous, with an interaural correlation of +1 or −1 (+1 and −1 control conditions), or shifted from one correlation to the other T-ms following signal offset (T = 2, 5, 10, 20, 40, 80, 160 ms). Relative to both control conditions, both postsignal correlation-shift conditions produced greater masking, with the amount of masking decreasing as a function of increasing values of T. The results are discussed in terms of the role of noise parameter stability in masking paradigms. [Research supported by grant NS 10995 from NINCDS.]
Fusion and consonance relations for tones with inharmonic partials
Authors: Cohen Elizabeth
Published: October 2005

Tones with inharmonic partials were generated on the Sampson Digital Synthesizer according to the algorithm. Fn = F1alog 2n, where Fn is the frequency of the nth partial and a determines the degree of stretching/shrinking of the octave. Subjects noted a bell or gonglike quality for stretched and shrunk tones. Subjects were asked to make judgments on the degree of fusion (unitary sensation of pitch). For individual tones a “pulling apart” of tones as a function of increasing a was discovered. Dyads, triads, melodic, and harmonic passages were also presented. Melodic relationships seem to hold throughout the range of 60% shrunk to 200% stretched (a = 1.2 → a = 4), whereas certain harmonic relationships break down. Preliminary results indicate that this harmonic breakdown is due to context and is not an individual property of the chord.
Is nonoccupational noise exposure negligible?
Authors: Schori T. R.
Published: October 2005

According to the Environmental Protection Agency's levels document (EPA, 1974), a daily noise exposure that does not exceed an Leq(24), of 70 dB can be considered, with an adequate margin of safety, a “safe exposure.” Furthermore, they suggested that restricting occupational noise exposure to an Leq(8), of 75 dB would be sufficient to protect the public since that would still result in an Leq(24), of 70 dB, provided that nonoccupational noise exposure is negligible? But is nonoccupational exposure negligible? Probably not. In this investigation, the noise exposure of 50 individuals was continuously monitored over seven consecutive days, by means of personal noise dosimeters. And, at least among these individuals, nonoccupational exposure was not negligible. In fact, when sleeping time was accounted for, nonoccupational noise exposure was often more significant than occupational exposure. [Work supported by USAF and EPA.]
Noise exposure in children and adolescents as measured by dosimetry
Authors: Siervogel R. M. , Himes J. H. , Roche A. F. , Johnson D. L.
Published: October 2005

Noise exposure over a 24-h period has been measured with portable dosimeters for 32 males and 30 females between 8 and 20 years of age. The mean Leq(24) was 80.9 dB, with a standard deviation of 6.04 dB. The regression of Leq(24) on age was 0.21 dB/year, although this is not statistically significant. The correlation between Leq(24), and the auditory thresholds at 1000, 2000, 4000, and 6000 Hz, while tending to be positive, were not statistically significant in either sex. However, in females a correlation of 0.32 (p = 0.09) was observed between thresholds at 4000 Hz and Leq(24), in males the corresponding correlation was −0.19 (p = 0.33). The group tested with the General Radio model 1954–9780 dosimeter had a mean (83.3 dB) significantly different from the groups tested with the Bruel and Kjaer model 4424 and the Loomis Laboratories model 3573 (78.6 and 76.9 dB, respectively) dosimeters. [Work supported by EPA and USAF.]
Statistical procedure for the determination of the daily noise dose
Authors: Myles Mark M.
Published: October 2005

The Daily Noise Dose (DND) is a single-member rating for measuring the degree to which a worker has been exposed to noise. But although it is a single number, the DND is based on a distribution of sound levels that is determined by the noise in the various environments where the worker may spend time. The DND thus obscures the statistical nature of worker noise exposure, and cannot, by itself. be used as an analytical tool for determining the relative contributions of the major sources of noise that the worker is exposed to. Furthermore, there typically is no estimate of the error or confidence in a given DND measurement. This paper will introduce the concept of an incremental noise dose dn, a random variable: derived from the sound level distribution. As a random variable, ordinary statistics such the mean and variance can be determined. Confidence intervals can be calculated as a measure of accuracy. Other sources of error, such as calibration error, sound level meter or dosimeter imprecision, and operator bias will be discussed.
Evaporation-condensation resonance frequency of oscillating vapor bubbles
Authors: Marston Philip L.
Published: October 2005

Approximations for the frequency of the new resonance of a small vapor bubble associated with evaporation and condensation are derived from the equations of “Vapor bubble dynamics” [R. D. Rinch and E. A. Neppiras, J. Acoust. Soc. Am. 53, 1402–1410 (1973)]. Previous predictions of the new resonance frequency ω, were obtained by numerically solving a secular equation. The purpose of the approximations is to elucidate the significant parameters; for example, the surface tension σ is predicted to greatly influence ω. When the liquid's thermal conductivity k is sufficiently large, ω is proportional to σ2/3R−8/3, where R is the equilibrium radius of the bubble; small k give ω proportional to σ2R−4. The approximations are substantiated by comparisons with numerical results for water, nitrogen, and helium. Criteria for their use depend on the relative magnitudes of the thermal diffusion length of the liquid, other liquid parameters, and R. Effects of evaporation-condensation resonance on radiation pressure and extinction of sound are suggested. Observed stable bubbles in helium [P. L. Marston and D. B. Greene, J. Acoust. Soc. Am. 64, 319–321 (1978)] are larger than those predicted for resonance. [Work partially performed at Yale University and supported by ONR.]
Creeping wave effects in the backscattered acoustic field from simple geometric shapes
Authors: Lang Mark S.
Published: October 2005

An experimental study designed to detect and measure the contribution of creeping waves to the acoustic field backscattered by simple geometric bodies was performed. The tests utilized acoustically hard models of cylinders, spheres, and prolate spheroids irradiated in air, where a very good approximation to the ideally rigid case can be obtained. The various scattering components were separated both by the use of pulse/gating techniques and by comparisons of data taken with a range of incident pulse lengths. Although some evidence of creeping wave effects was noted near the model surfaces, the expected backscattered components could not be found in the returned field of any of the models. These results seem to reduce the practical significance of the concept of creeping waves as diffraction rays which interfere with specular and edge-formed rays to create the total backscattered field. [Work supported by NAVSEA.]
T-matrix formulation of acoustic wave scattering by elastic or viscoelastic obstacles of arbitrary shape immersed in a fluid
Authors: Peterson Bo , Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

A new scattering matrix theory is developed for investigating the scattering of acoustic waves by elastic or viscoelastic obstacles of arbitrary shape immersed in a fluid. The problem is difficult since the Q matrix obtained in the usual way is not square and hence cannot be inverted. In this paper, a T-matrix formalism is presented by considering additional representations of the scattered and refracted fields so that one arrives at matrix equations that are invertible. Numerical results for the scattering cross sections of prolate, oblate, and spherical obstacles immersed in water are presented as a function of the dimensionless wave number.
Intonation synthesis based on metrical grids
Authors: Pierre-humbert Janet
Published: October 2005

A new approach to synthesizing intonation has been developed which makes use of recent advances in linguistics in the description of stress and intonation. To synthesize an unmarked declarative F0 contour, the system assigns peaks of different heights to stressed syllables entirely on the basis of a metrical grid for the utterance, which can be constructed from its syntax [Liberman and Prince, “On Stress and Linguistic Rhythm,” Linguistic Inquiry 8, (1977)]. The system makes use of a sagging principle of interpolation which determines the F0 and location in time of a local minimum as a function of separation in height and time of adjacent peaks. This innovation makes it possible to generate very natural F0 contours without reference to word or syllable boundaries. Because the system has been based on linguistic analysis of a variety of intonation patterns, it has the further advantage that it can be extended in a straightforward manner to synthesize marked intonation patterns as well as neutral declarative intonation. The program is demonstrated with LPC speech whose F0 contours have been replaced by synthetic F0 contours, retaining the original durations. [Work carried out at Bell Laboratories.]
Rational filter design with special reference to speech synthesis
Authors: Arcese A. , Goldberg A. J.
Published: October 2005

In this paper we consider the design of filters with a rational function z transform. This pole-zero representation corresponds to an autoregressive moving average in the time domain. Two methods based on least squares and a third method based on a bounded error constraint are given. Numerical results for speech waveforms are presented.
A language and multitasking operating system to support an eight channel speech input terminal
Authors: Glazer S.
Published: October 2005

A speech input terminal must be able to carry on a natural conversation with a user. This presents several special problems for the designer of the terminal's operating system. Multiple channels must be handled independently and must not interact with other channels. Timing must be sufficiently precise so that there are no unnecessary pauses before listening or speaking. Changes must be easy to implement in order to experimentally optimize the human factors aspects of the conversation. The system must lend itself to modularization and easy documentation. These issues are discussed and the language and operating system used at Dialog are presented.
Intensity discrimination and loudness matches in observers with sensorineural hearing loss
Authors: Florentine M. , Reed C. , Durlach N. I. , Braida L. D.
Published: October 2005

Intensity discrimination and loudness matches were determined as a function of level in observers with sensorineural hearing loss of primarily cochlear origin. For observers with unilateral impairments, tests were made at the same frequency in the normal and impaired ear. For observers with bilateral-sloping losses, tests were made at different frequencies in the same ear. The stimuli were 500-ms tones with a rise-fall time of 25 ms and interstimulus interval of 200 ms. The results suggest that hearing loss (even with recruitment) does not reduce the difference limen provided the comparison is made at the same sound pressure level. In general, the difference limens in normal and impaired hearing appear more similar at equal loudness levels than at equal sound pressure levels or at equal sensation levels. Also, the loudness matching data appear to be at least roughly consistent with the predictions derived from the discrimination data using the proportional-jnd theory of loudness matching [J. S. Lim, W. M. Rabinowitz, L. D. Braida, and N. I. Durlach, J. Acoust. Soc. Am. 62, 1256–1267 (1977)]. [Work supported by NIH.]
Interaural time discrimination and brain stem potentials in patients with multiple sclerosis
Authors: Levine R. A. , Hausler R.
Published: October 2005

Twenty-nine patients with multiple sclerosis who had normal audiograms and good speech discrimination were studied. A two-alternative forced choice paradigm was used to determine interaural time and intensity JNDs for white noise bursts. Short-latency (< l0 ms) click evoked potentials were recorded between the vertex and earlobe. The subjects with normal interaural time JNDs usually had normal responses even if the interaural intensity JNDs were abnormally large. Those with abnormally long time JNDs usually had abnormal evoked responses; those with the longest time JNDs often exhibited no waves beyond the compound action potential of the auditory nerve. Patients with abnormal time JNDs and different evoked potentials on stimulating each ear showed a lateralization bias: whenever the interaural time of the stimulus was less than the subject's time JND the stimulus was localized towards the side for which potentials were more normal. [Supported by NIH and the Hôpital Cantonal of Geneva, Switzerland.]
Vowel temporal masking of pitch recognition for consonant-like noise bursts by normal- and impaired-hearing listeners
Authors: Revoile S. , Holden Lisa D. , Brandt Fred , Pickett J. M.
Published: October 2005

Impaired- and normal-hearing subjects (Ss) identified the pitch of either a low-, mid-, or high-frequency noise burst in a recognition-masking task with a two-formant vowel masker which preceded and/or followed the noise burst. F1 of the vowel was at 700 Hz and F2 at 1100 Hz. The three noise bursts were bands of flat-spectrum noise: 500–1500 Hz, 1500–4000 Hz, or 4000–6000 Hz. Forward-, backward-, and combined-forward-and-backward-masking conditions were tested with a 10 ms Δt. The vowel was presented at most comfortable listening level (MCL) for the impaired and at 90 dB SPL for the normal-hearing Ss: the noise bursts were presented at 10 dB SL. Pitch recognition of the noise bursts was affected least in the backward-masking condition and was poorest in the combined-forward-and-backward-masking condition. In the combined masking condition nearly all Ss showed some masking of pitch recognition for one or more of the noise bursts. Masking occurred most often for the low-frequency burst and least often for the high-frequency burst. Generally, release from masking was seen when Δt was lengthened to 100 ms.
Frequency shaping and multiband compression in hearing aids
Authors: Abramoritz Rachelle
Published: October 2005

Compression and noncompression amplification were compared for a range of conditions. The noncompression conditions included flat-frequency response and “LDL frequency response,” with and without peak clipping. The compression conditions included a single-band compression system and four combinations of a two-channel compression system. The LDL frequency response was obtained by finding the LDL for each subject using one-third octave bands of noise and then determining that frequency response which will amplify each third-octave band of speech to just below the LDL for that band. A low-frequency roll off below 300 Hz is used to reduce upward spread of masking. Four hearing impaired persons served as subjects. Four replications of the Nonsense Syllable Test were administered in quiet and in noise for each experimental condition. The highest scores were obtained, on average, for the noncompression, LDL frequency response, no peak clipping condition. There were, however, large individual differences in relative performance on different conditions, indicating the importance of individualized determination of optimum amplification characteristics.
An evaluation of Optacon-based tactile speech displays
Authors: Clements M. A. , Mook D. R.
Published: October 2005

Two experiments were conducted in which short-term speech spectra were presented via the tactile Optacon transducer system. In the first experiment four subjects were trained to identify a set of twelve consonants in CV nonsense syllables spoken by four talkers. A tactile display coding frequency and amplitude was compared to a visual display of the same information. For comparable amounts of training, visual performance was always better than tactile, but this difference decreased as training increased. For both displays, performance was highest for voicing and poorest for place. A second study tested the discriminability of forty-five pairs of vowels using frequency-amplitude and frequency-time displays. In general, similar results were obtained on the two systems, although average scores were slightly better on the frequency-time display. The most salient cues used to discriminate vowels appeared to be first-formant frequency, duration, and amplitude. [Work supported by the Edith E. Sturgis Foundation and by NSF.]
Vibrotactile reception of transformed voice fundamental frequency
Authors: Rothenberg M. , Molitor R. D.
Published: October 2005

Deaf and hearing subjects were asked to identify the stress pattern in a short sentence from the variation in voice fundamental frequency (F0) when presented aurally (for hearing subjects) and when transformed into vibrotactile pulse frequency (for both groups). Various transformations from F0 to pulse frequency were tested. The results indicated that a one- or two-octave reduction of F0 to vibrotactile frequency (transmitting every second or third glottal pulse) might result in a significant ability to discriminate the intonation patterns associated with moderate-to-strong patterns of sentence stress in English, for a wide range of speakers. However, the reception of the details of the intonation pattern may be masked by an apparent temporal indeterminancy of about 125 ms noted in the perception of variations in vibrotactile frequency. The results also offered some limited support for our previous hypothesis that there is a natural association between auditory pitch and perceived vibrotactile frequency. [Work supported by NIH.]
Computer-assisted hearing-aid selection
Authors: Hertzano Talma , Levitt Harry , Slosberg Ronald
Published: October 2005

Measurements of frequency response, maximum peak-to-valley deviation (ripple) in the frequency response, percent harmonic distortion and saturation sound pressure levels as measured on a standard 2-cc coupler for a set of commercially available hearing aids are entered into a small computer. A similar set of measurements on the same coupler is obtained for a reference hearing aid which, in this case, is a wearable master hearing aid set to the flat-frequency-response condition. A first estimate of the optimum frequency response for the subject is determined using the master hearing aid. The difference between this frequency response and that of the reference aid is used by the computer to select a small set of commerical hearing aids whose characteristics approximate most closely those of the estimated optimum characteristics. Constraints are imposed on the computer search procedure with respect to maximum allowable distortion, ripple in the frequency-response, and saturation sound pressure levels. Speech discrimination in noise is measured and the aid yielding the highest score is selected. [Research supported by NINCDS.]
Low-frequency interaural time differences and available localization cues in the azimuthal plane for listeners with head-worn or body-worn hearing aid(s)
Authors: Kuhn George F. , Munro Tom
Published: October 2005

The interaural time differences (ITD), the primary low-frequency localization cues are determined for head-worn and body-worn hearing aids as a function of location and angle of incidence. The ITD's are predicted on the basis of scattering theories for a rigid sphere and cylinder for head-worn and body-worn hearing aids, respectively. The results show that the range of the available localization cues (ITD's) for aided listeners is compressed, yielding a smaller range of cues than that available to unaided listeners. The “apparent angle of incidence” for monaurally aided listeners is shown to be increasingly offset from the true angle of incidence as the hearing aid(s) is worn forward of the earcanal axis. This bivaluedness, which occurs principally when the angle of incidence relative to frontal incidence becomes large or when the hearing aid(s) is located considerably forward of the earcanal axis, yields confusion localization cues. The results also show that body-worn hearing aids can produce ITD's similar to those for unaided listeners if the aids are spaced symmetrically about the median plane of the torso, a distance of ∼22 cm apart. Comparisons of predicted ITD's with published clinical and subjective localization studies for aided listeners are self-consistent and in good agreement.
Clinical variations in headband tension and potential effects on audiometric thresholds
Authors: Craig C. H. , Bienvenue G. R. , Michael P. L. , Kohut A.
Published: October 2005

The calibration of a standard audiometric headset is dependent upon headband tension. Similarly the attenuation provided by this standard, supra-aural headset is dependent upon the headband tension, and headband tension may change observably during clinical use. This is especially pertinent when one considers that masking from background noise is a serious problem when hearing levels are measured at or near the low reference threshold levels specified in the American National Standards Specifications for Audiometers, ANSI S3.6-1969. In the present study the degree of headband tension change during clinical threshold audiometry has been measured empirically. In addition the effect of these tension changes upon the obtained pure-tone thresholds at several frequencies were determined. Significant differences in obtained thresholds contingent upon deterioration of headband tension were noted. Results of this experiment will be discussed by reference to modeling of the acoustic impedance characteristics of a simple, single-cavity audiometric headset.
Tone noise of three supersonic helical tip speed propellers in a wind tunnel
Authors: Dittmar J. H. , Blaha Bernard J. , Jeracki Robert J.
Published: October 2005

A high tip speed turboprop is being considered as a future energy conservative airplane. When the turboprop airplane is at cruise, the combination of the airplane forward speed and the propeller rotational speed results in supersonic helical velocities over the other portions of the propeller blades. These supersonic blade sections could generate noise that is a cabin environment problem. Three 0.622 m (24.5 in.) diam propellers were acoustically tested in the NASA Lewis 8-by 6-ft. wind tunnel. This wind tunnel does not have acoustic damping material on its walls and is therefore not an ideal location for taking noise data. However, it was felt that information obtained about the noise differences among the three propellers would be useable. The propellers were tested at tunnel through flow Mach numbers of 0.6, 0.7, 0.75, 0.8, and 0.85 with different rotational speed and blade setting angles. The three propellers incorporated different plan forms and different amounts of sweep and yielded different noise levels. The acoustically designed propeller had 45° of tip sweep and was significantly quieter than the straight bladed propeller. The intermediate 30° tip sweep propeller exhibited noise that was between the other two blades. Noise trends with varying helical tip Mach number and blade loading were also observed.
Higher order mode effects in circular ducts and expansion chambers
Authors: Eriksson L. J.
Published: October 2005

The theory of higher order modes in circular ducts is reviewed and applied to expansion chambers. Numerous schemes have been proposed for use in labeling the various higher-order modes in a circular duct. This has led to confusion and, in at least one case to erroneous descriptions of the higher-order modes. In an attempt to solve this problem, a specific approach, analogous to that used in rectangular ducts, is proposed that has geometric clarity and elegance. The cutoff frequencies for these various modes are discussed with respect to propagation in an expansion chamber. Incomplete and misleading statements in the literature concerning the calculation of cutoff frequencies are reviewed. Higher order mode propagation through an expansion chamber is analyzed for various inlet and outlet locations, and experimental results presented. The interaction between plane wave and higher-order mode effects is discussed.
Replacement of perilymph with K+-free media abolishes positive endocochlear potential (guinea pig)
Authors: Marcus D. C. , Marcus N. Y. , Thalmann R.
Published: October 2005

Perfusion of the perilymphatic space with K+-free media leads to a gradual decline of the endocochlear potential (EP) to negative values near those observed during anoxia. The input resistance of scala media does not decrease during this time. In sharp contrast to anoxia, the ATP content of the stria vascularis (SV) remains near normal during K+-free perfusion (85%). Thus, a significant interference with strial energy generation appears unlikely. Following K+-free perfusion, the K+ content of the spiral ligament (SL) was reduced from 227 to 59 and that of the SV from 410 to 266 mmoles/kg dry wt. The pronounced reduction of the K+ content of the SL indicates that the perfusate reaches the lateral wall of the SV. These results demonstrate that a reduction of the [K+] of perilymph leads to an inhibition of the generator of the positive component of the EP. If it is true that the SV is responsible for the production of the +EP, the results suggest furthermore that K+, contained in the strial capillaries, may not have access to the generator of this potential. [Supported by NIH and NSF.]
Effect of carbohydrate depletion upon endolymphatic potential
Authors: Wada J. , Kambayashi J. , DeMott J. I. , Thalmann I. , Thalmann R.
Published: October 2005

Near normal levels of the endolymphatic potential (EP) of the guinea pig can be maintained for at least 3 h by perfusion of the anterior inferior cerebellar artery with “artificial blood,” composed of a perfluorochemical (FC 47) as oxygen carrier suspended in a physiological salt solution containing glucose [Wada et al., Laryngoscope, 1979, in press]. [We have now determined that glucose can be omitted from the medium, without deleterious effect upon the EP for periods exceeding 90 minutes. Apparently, the stria vascularis—the presumed generator of the EP—can maintain its function by relying upon its rich store of endogenous glycogen. However, by means of repeated hypoxic intervals, induced by interrupting perfusion, the glycolytic flux can be accelerated, thus expediting depletion of endogenous glycogen. Following several bouts of hypoxia, the substrate stores are reduced to the point that the EP starts declining at a constant rate of about 1 mV/min during glucose free perfusion. This decline can be reversed by applying a glucose (or succinate) containing medium. The rate and degree of recovery depend upon the glucose (or succinate) concentration in the medium. [Supported by NIH and NSF.]
Cyclic nucleotides in guinea pig cochlea
Authors: Thalmann I. , Paloheimo S. , Thalmann R.
Published: October 2005

The cyclic nucleotides cAMP and cGMP play a universal role as “second messengers” in biological systems, e.g., in sensory transduction in the retina, neural transmission in several synaptic systems, and regulation of transport processes in secretory organs. The distribution and potential role of cAMP and cGMP in the organ of Corti (OC) has been discussed recently [R. Thalmann et al., Acta Otolaryng., 1979, in press]. In the stria vascularis (SV) the cAMP concentration is about 17× higher than that of cGMP [4190 and 240 units (nanomoles/kg dry wt), respectively]. The difference is less pronounced in the spiral ligament (1310 and 302 units, respectively). Surprising is the high concentration of cAMP in Reissner's membrane (3340 units, 28× the cGMP concentration of 121 units). Pharmacological studies indicate that perilymphatic application of ethacrynic acid leads to a significant reduction of strial cAMP, in agreement with its inhibitory effect upon strial adenylate cyclase. Perilymphatic application of nitrosamines increases cGMP in OC, SV, and Reissner's membrane about 20×, suggesting a substantial activity of particulate guanylate cyclase. [Supported by NIH and NSF.]
Analysis of the “paired-click” method for determining linear filtering properties of auditory neurons
Authors: Pick G. F. , Narins P. M.
Published: October 2005

The “paired-click” technique for characterizing the linear filtering properties exhibited by single neurons of the auditory system was examined. This method, as described by Møller [Acta Physiol. Scand. 78, 299–314 (1970)], makes use of an acoustic stimulus consisting of two clicks, of the same or opposite polarity, separated by time Δt;; the number of neural spikes evoked by the click pair is measured as a function of Δt. From this measurement, the autocorrelation function of the linear part of the system and its Fourier transform (the energy response of the system) may be determined. Using an analytical treatment of the technique supplemented with a computer simulation model, we show that only if the system contains an even-order nonlinearity does the method yield the characterizing autocorrelation function. Moreover, unless the nonlinearity is purely quadratic, the autocorrelation function is “contaminated” by higher-order terms. In addition, the effect of the “equivalent stimulus intensity” transformation and the amplitude of the click pair is examined.
Citizen participation in the public policy issues involving acoustical science and technology
Authors: Jhaveri Arun G.
Published: October 2005

Citizen participation in scientific and technological decision making has only recently been recognized as an essential ingredient of the overall democratic governmental process, affecting millions of people in this country and abroad. Examples of significant national debates involving bureaucrats, professionals and public at large during the nineteen seventies on such major issues as nuclear power, DNA research and environmental pollution, provide the basis for similar dialogues in the future on other science and technology activities of regional and national concern, impact or controversy. Among these new candidates is the one involving acoustical science and technology. This paper attempts to identify and analyze those controversial programs and activities within the acoustics field that might have significant impact on the present and future course of governmental decision-making process. In addition, the author proposes a few models/mechanisms that might help facilitate intelligent and constructive dialog between the nontechnical community on one side and scientific/technological community on the other, hopefully resulting in realistic, acceptable, and manageable decisions at all levels of public/government interactions. The two acoustical science and technology areas specifically discussed are environmental/occupational noise and medical ultrasonics vis-a-vis their associated public policy issues of health, welfare, and safety.
Logarithmic hazards of acoustical calculations
Authors: Eichler Ewald
Published: October 2005

Many of the logarithmic (or decibel) equations used in noise control are derived from nonlogarithmic physical equations by approximations that are not readily apparent. Such approximations involve numerical substitutions for physical quantities or the dropping of physically additive terms which are not conveniently rendered logarithmically. In consequence, the basic physical equations may be obscured and the user of the equation may be misled. For example, an error of the atmospheric-pressure correction in Standard ISO 3741, which should have been apparent on dimensional grounds in the underlying physical equation, went unnoticed for years. While those approximations may be justifiable for many applications, they need not be so for others: several examples are furnished by the field of sound isolation of partitions and enclosures. In order to forestall such slips, we ought to confine logarithmic relations and “quantities” to a concomitant, ancillary, or proxy position with respect to their physical counterparts. The general public, too, who keep merging sound-pressure level and sound-power level into one vexing sound level may find it possible to distinguish between sound pressure and sound power if we help them.
Chronic N1 thresholds in chinchilla
Authors: Harris D. M. , Geller H. S. , Halpern L. D. , Koch D. B.
Published: October 2005

Whole nerve compound action potentials (APs) are used to determine AP threshold curves of individual chinchillas. Initially, each animal is implanted with a chronic round window electrode that is connected to a small plug fastened to the skull. After recovery from surgery the animal is suspended in an anechoic chamber and presented with free-field tone-bursts. Computer-averaged APs (N = 128), monitored on an oscilloscope, are used for visual detection of N1, thresholds for several tone-burst frequencies from 0.5 to 20 kHz. In this manner, a threshold curve is determined on the basis of data accumulated over at least four separate days. Animals considered to have normal thresholds are then placed on a kanamycin regimen. Kanamycin, an ototoxic antibiotic, produces a lesion that progresses through the cochlea from base to apex, preferentially destroying outer hair cells; hence, the first effects of the drug are manifest as a threshold shift at higher frequencies. Animals receiving kanamycin injections are monitored daily in the same manner that established their initial threshold curves. The extent of cochlear damage is reflected in postkanamycin threshold curves. [Work supported by NINCDS.]
Effect of helicopter noise spectra on annoyance of passengers
Authors: Clevenson Sherman A. , Leatherwood Jack D.
Published: October 2005

The annoyance of passengers to helicopter noise was investigated by exposing subjects to simulated helicopter noises in the NASA Passenger Ride Quality Apparatus. The passengers were subjected to the measured internal noise of the NASA Civil Helicopter Research Aircraft and to five filtered conditions of the noise, each at four noise levels. In addition, the subjects were given an incentive to identify a series of phonetically balanced (PB) words prior to recording their annoyance. Each subject experienced each condition at four levels ranging from 70 to 86 dBA. Removal of the gear-clash or other predominant-frequency components reduced the noise level and the annoyance ratings of the subjects. The annoyance was essentially the same for a given noise level with or without the gear-clash or other predominant-frequency components. For identical noise conditions, the annoyance was greater when the passenger-subjects were attempting to identify PB words.
Ultrasonic standing wave modes in axially stressed rods
Authors: Heyman Joseph S. , Cantrell John H.
Published: October 2005

Ultrasonic propagation in axially stressed metal resonators is examined from the standpoint of a propagating plane wave model. The theoretical results are compared with experimental data obtained with a new resonant instrument called an Ultrasonic Bolt Tensioning Monitor, capable of resolving changes in stress of less than 104 Pa (1 lb./in.2). The applied load produces a coupling to the acoustic resonant modes via a stress induced strain as well as a stress induced change in sound velocity. The coupling is shown to produce a linear relationship between load and resonant frequency characterized by a continuous wave stress acoustic constant R. Some geometrical considerations may impact R and are considered. For example, non-parallelism is shown to have produced a severe degradation of signal for conventional transducers, and the accompanying stress gradients alter the value of R. Also, the percentage of length actually under load changes R and is shown to produce an effect predicted by the plane wave model. In addition to the linear data obtained with the ultrasonic tension instrument, spectral characteristics of the samples are presented.
Hair-cell receptor modeling
Authors: Dolmazon J. M. , Bastet L.
Published: October 2005

For studying the various hypothesis about hair cell functions, a new computational model of inner-ear sensory receptors have been developed and coupled with our analog model for motion of the basilar membrane. Each kind of receptors can be represented by a transfert function corresponding to a velocity or displacement transducer. Connections between these two kinds of sensory receptors and nerve fibers are done in light of neuroanatomical data about hair cell innervation, taking into account propagation delay along nerve structures. Interaction between inner and outer hair cells has been also investigated. Several aspects of auditory nerve fiber activity have been reproduced in this model such as sharpening of mechanical tuning curves, transient responses exhibit by nerve fibers, phase sensitive behavior of neurones with direction of basilar membrane motion and some properties of two-tone inhibition. Thus, the significance of each parameter of the model can be explained and a feedback can be made on primary hypothesis about inner-ear transducer processing. [Work supported by E.R.A. C.N.R.S. No. 366.]
A model of mechanical to neural transduction
Authors: Searle C. L. , Schwalm C. L. , Kimberley B. P.
Published: October 2005

There are several experiments involving single-cell recording which are clearly measuring peripheral processes only (i.e., do not involve efferent action): steady-state rate functions versus amplitude, click response PST histograms, sine-wave tuning curves, envelope response to brief noise and tone pulses, steady-state two-tone inhibition, envelope response to steady tone plus inhibiting tone pulse, and transient response to closely spaced click pairs. Ideally, one would like to construct a model of the mechanical to neural transduction process which encompasses all of the above results. Several models have appeared in the literature over the past 15 years, but each matches only a limited set of experiments. However, we have combined the most promising features of several of these models to synthesize a new model which at least qualitatively matches all of the experimental data listed above except the click-pair experiments, and has some physiological validity. Detailed comparisons between experimental data and computer generated simulations will be presented. [Supported by Defense and Civil Institute of Environmental Medicine.]
High-frequency fields excited by a source in an underwater surface duct
Authors: Felsen L. B. , Ishihara T. , Cho S. H.
Published: October 2005

High-frequency fields in an underwater surface duct with monotonic velocity profile in depth cannot be expressed solely in terms of ray contributions when transmitter and receiver are both located on or near the surface since the caustics of rays with many reflections pile up near the surface. However, it is possible to employ a hybrid formulation in terms of a truncated ray series and an appropriately chosen number of tightly bound surface waves [L. B. Felsen and T. Ishihara, J. Acoust. Soc. Am. (to be published)]. As the receiver moves sufficiently far into the duct interior, it is no longer reached by rays undergoing many reflections. Ray acoustics alone, properly corrected near (isolated) caustics, should then provide an adequate description. This is confirmed by a detailed numerical study of the field as a function of range and depth, with data calculated from various representations involving normal mode expansions, ray acoustics, a “canonical integral” formulation. and the ray-mode mixture. It is also shown that even when ray acoustics is adequate, a hybrid ray-mode combination can be chosen so as to avoid the caustic correction problem entirely. [Work supported by ONR.]