bluuebunny/crossref_metadata_2025 huggingface dataset:
Partial masking and pitch shifts in impaired ears
Authors: Burns Edward M.
Published: October 2005

In a previous paper [Burns and Oesterle, J. Acoust. Soc. Am. Suppl. 1 67, S20 (1980)] we reported on an experiment in which the pitch shift, loudness reduction, and reduction in (nonsimultaneous) masking effectiveness of pure tones were measured as a function of the spectrum level of a broadband noise masker in normal hearing subjects. There was, in general, not a good correlation between the amount of pitch shift and the amount of loudness reduction or the amount of reduction in masking effectiveness. For example, significant differences in the magnitudes of pitch shifts in the two ears of a given subject were not reflected in the measurements of partial masking. The present paper reports on a similar experiment performed on observers with various configurations of sensorineural hearing losses. The results show more dramatically the lack of correlation between partial masking and pitch shifts. In a number of cases normal or exaggerated pitch shifts were found with little or no partial masking being evident. In other cases gross differences in the pitch shifts between the two ears were found whereas partial masking was virtually identical in the two ears.
Intensity discrimination of simple and complex stimuli
Authors: Buus Søren , Florentine Mary
Published: October 2005

Difference limens (DLs) were measured at 30, 60, and 75 dB SPL per critical band. The stimuli were a 1000-Hz tone, a partially-masked 1000-Hz tone, an 18-tone complex consisting of equally intense harmonics (F0 = 110 Hz) encompassing frequencies from 110 to 7260 Hz, and a uniformly masking noise. The DLs were measured in a 2I, 2AFC paradigm with an adaptive procedure. The stimulus duration was 500 ms; the interstimulus interval was 250 ms. The results for the three listeners are very similar. The DLs for the pure tone decrease from 1.3 dB at 30 dB SPL to between 0.33 and 0.7 dB at 75 dB SPL. The DLs for the partially masked tone stay relatively constant around 1 to 1.6 dB with increasing level, except for one listener whose DL at 75 dB SPL is clearly smaller than at the lower levels. The results for the noise and the tone complex are similar, showing little level dependence with DLs between 0.4 and 0.8 dB. Generally, these results are consistent with the multi-band excitation-pattern model [Florentine and Buus, J. Acoust. Soc. Am. Suppl. 1 67, S22 (1980)].
Interaural time determination in tonal maskers
Authors: Kaiser Donald L. , Stern Richard M.
Published: October 2005

Just-noticeable differences (jnds) of interaural time delay were measured for 55-dB SPL 500-Hz tonal targets in the presence of various binaural tonal maskers. The maskers were simultaneously presented with equal amplitude and either 0 or 180 deg interaural phase shift, and data were collected over a range of target-to-masker ratios and masker frequencies. In general, better discrimination performance (smaller jnds) was observed when the maskers were presented with 0 degrees interaural phase, which is consistent with results from several recent studies using broadband maskers. The jnds decrease and become less dependent on interaural masker phase as the frequency separation between target and masker increases. Both the lateralization model and the position-variable model based on auditory-nerve activity are able to predict the correct dependence of the jnds on the interaural masker phase. These models are presently being extended to enable a comparison of their predictions to the dependence of the jnds on masker frequency. [Supported by NIH.]
Effect of pre-trial adaptors on the discrimination of a brief time interval between tone burst pairs
Authors: Divenyi Pierre L. , Robertson Lynn C.
Published: October 2005

Trained listeners were asked to discriminate, in a 2AFC paradigm, a nominally zero duration and a longer gap marked by a 10-ms and a 100-ms tone burst. Confirming earlier results (Divenyi and Sachs, Perc. Psychophys. 24, 429–436 [1978]), the average duration of a just discriminable (d′ = 1.0) gap was found to be 0.87 ms when the frequency of both markers was fixed at 1 kHz (the Δf = 0 condition), whereas it increased to 5.1 ms when the frequency of the first marker was 2 kHz and that of the second was 500 Hz (the Δf = 2 octave condition). In subsequent experiments the stimulus in each trial was preceded by three presentations of an “adaptor” sound. The duration of each adaptor was 300 ms and each of them was followed by a 150-ms silent interval. Adaptors were either tone bursts (0.5, 1, or 2 kHz) or bursts of bandpass noise (0.5 to 2 kHz). Within each block of trials only one type of adaptor sound was used. Long on- and offset ramps (50 ms) attempted to minimize the timing cues in the adaptors. In the Δf = 0 condition the noise adaptors caused the gap discrimination threshold to significantly increase (with respect to the condition in which no adaptor was present). In contrast, the tone adaptors in this condition slightly decreased the threshold, the 1-kHz adaptor having the largest facilitating effect. On the other hand, in the condition where the markers were separated by 2 octaves all adaptors improved the gap discrimination performance. The 2-kHz adaptors (i.e., those the frequency of which coincided with that of the very brief first marker) yielded the lowest average threshold (1.6 ms), whereas the noise and the 500-Hz adaptors produced the highest (2.0 and 1.9 ms, respectively). The results indicate that (i) pre-trial adaptors may have large facilitating effects on time-oriented auditory tasks, and that (ii) these effects are largest when the adaptor cues the subject to listen in a frequency band in which the time marker is weak. Possible relevance of these data to the perception of brief time intervals in speech will be discussed.
Subharmonics, bifurcations. chaos and all that jazz
Authors: Rudnick Isadore , Keolian Robert
Published: October 2005

In this, the sesquicentennial of the publication of Faraday's landmark experimental observation [M. Faraday, Philos. Trans. R. Soc. (London) 299 (1831), Sec. 103; Lord Rayleigh, The Theory of Sound (Dover, New York, 1945), Sec.68b] of the subharmonic, f/2, in the crispations generated on a flat horizontal plate wet with water when it is oscillated vertically at a frequency f, we report on the results of a version of this experiment where we observe subharmonics of frequency f/m where m, at this writing, has been observed to have the values 2, 4, 12, 14, 16, 18, 20, 24, 28, 30, 32, 34, 35. Moreover harmonics of these subharmonics occur in profusion so that the frequencies which appear in an FFT graph are given by pf/m, where p is an integer which can reach values as high and higher than 2 m. The transition to a chaotic [Physics Today 34, 17 (March 1981)] or turbulent state is observed.
Characterization of molecular binding from ultrasonic non-linearity parameters
Authors: Cantrell John H.
Published: October 2005

The description of antharmonic properties of solids involves generalized Grüneisen parameters which describe the strain dependence of the lattice vibrational frequencies. A quantitative measure of solid anharmonicity, the ultrasonic nonlinearity parameter, is obtained directly from ultrasonic harmonic generation experiments and has been shown to be linearly related to the isentropic generalized Grüneisen parameter [John H. Cantrell, Jr., Phys. Rev. B 21, 4191 (1980)]. Although solid nonlinearity parameters have been measured in relatively few materials they can be calculated for many solids from published measurements of the pressure derivatives of second-order elastic coefficients. We have used these data to calculate the ultrasonic nonlinearity parameters and the corresponding isentropic Grüneisen parameters for a number of crystalline solids of cubic symmetry. The calculations indicate a strong correlation between the value of the isentropic mode Grüneisen parameter and the type of crystalline binding. For example, the [100] mode Grüneisen parameters cluster around 7.3 for ionic crystals, 1.1 for covalent crystals, 3.0 for fcc metals, and 11.5 for bcc metals. The implications of these results are discussed.
Cochlear nonlinearity: The effect of two tones on permanent threshold shift
Authors: Johnstone Brian M.
Published: October 2005

Using N1 as the response criterion in guinea pig; two loud tones presented simultaneously give much less PTS than either alone.
Characterization of basilar membrane nonlinearity using the “slope function”
Authors: Le Page Eric L. , Johnstone Brian M.
Published: October 2005

Recent capacitive probe measurements have revealed a vulnerable nonlinearity in the motion of the basilar membrane in the guinea pig cochlea [E. L. Le Page and B. M. Johnstone, Hear. Res. 2, 183–189 (1980)]. It is possible to extract a consistent characterization of the nonlinearity in terms of a “slope function”—a smoothed plot of the input-output slope (dB/dB) versus frequency. Whereas the response magnitude function is essentially that of a low-pass filter, the slope function shows compression (i.e., slopes < 1 dB/dB) which is localized and maximal just above the cutoff frequency Fco, at a frequency Fcm. The lower frequency limit of the compression is 0.55 +/− 0.1 octaves below Fcm. Above Fcm there is a rapid transition from compression to expansion (i.e., slopes > 1 dB/dB). The slope function exhibits similar features whether obtained from sinusoidal stimuli or from click responses via Fourier transformation. Its shape depends on stimulus level; as the click level is reduced, the slope function shows less overall compression along with a decrease in Fcm. As the preparation deteriorates, the slope function is flattened but the expansion remains; the degree of compression is reduced, and the frequency at which the function becomes expansive decreases, resulting in a decrease of Fcm.
Short-term vulnerability and variability of basilar membrane nonlinearity
Authors: Le Page Eric L. , Johnstone Brian M.
Published: October 2005

A capacitive probe study of guinea pig basilar membrane non-linearity in the guinea pig [E. L. Le Page and B. M. Johnstone, Hear. Res. 2, 183–189 (1980); E. L. Le Page and B. M. Johnstone, J. Acoust. Soc. Am. Suppl. 1 67, S45 (1980)] showed that the decline of compression (i.e., the return to linearity at the cutoff frequency) was correlated (r = +0.7, t = 5.2) with a long-term loss of neural sensitivity as determined by the N1 response to tone bursts at the cutoff frequency. Sequences of mechanical records reveal rapid changes in the magnitude response functions, but the pattern of change of the ‘slope function’ [E. L. Le Page and B. M. Johnstone (accompanying abstract)] is reproducible. The general shape of the slope function is preserved, but the loss of compression is accompanied by a decrease in the frequency of maximal compression, Fcm. Exposure to high-level tones produce an immediate flattening of the slope function. Recorded examples of recovery suggest that the compression mechanism has been temporarily disabled, in contrast to the permanent loss incurred by poor dissection or death. This suggests that the variability in these data may be related to a heightened susceptibility to neural sensitivity loss with exposure to the click stimulus when scala tympani is drained of perilymph. These results suggest that the description of cochlear nonlinearities may depend significantly on the experimental protocol, particularly with regard to the use of high level stimuli.
Interfacial tension between water and superheated liquids
Authors: Hsu Chaur-Jian , Apfel Robert E.
Published: October 2005

We have measured the interfacial tension between water and superheated liquids by using a technique similar to that described by Marston and Apfel [J. Acoust. Soc. Am. 67, 27–37 (1980)] in which the interfacial tension can be deduced from the quadrupole resonance properties of a liquid drop immersed in an immiscible host liquid. Several aspects of this technique are advantageous for studying the properties of superheated liquids. In particular, the host liquid provides a smooth and clean container for the levitated sample drop. Moreover, the shape oscillation is excited by modulating the acoustic radiation pressure on the drop, thereby avoiding contact with solid surfaces which would trigger drop vaporization. The deformation of mm-radius drops was detected optically using a method similar to Trinh, Zwern, and Wang [to be published]. We shall discuss some of the modifications of the measurement techniques from those of previous investigators. Preliminary results will be presented and are compared with other available data. [Work supported by ONR, Physics Program.]
A nonuniformly heated resonant chamber for levitation studies in air
Authors: Trinh E. , Wang T. G. , Robey J.
Published: October 2005

The resonance conditions of an elongated vertical chamber with a square cross section and a significant temperature gradient along its main axis obtained by heating its upper part, have been experimentally determined in the course of the development of a dual temperature levitation apparatus. Under the present conditions, the cavity can be roughly divided into three main regions: the bottom and top portions arc at a relatively uniform low and high temperature, respectively, and the middle region is a transition zone with a sharp temperature gradient. The spectrum of resonance for modes with wave vectors both parallel and perpendicular to the direction of the thermal gradient has been determined with sensors in the cool as well as the hot regions. Conditions appropriate for levitation have been found in both these portions, and revealed that the required modes having wave vectors perpendicular to the temperature gradient are determined to a large extent by the local conditions, while the modes with wave vectors parallel are dependent upon the overall temperature distribution within the chamber. Levitation of low density solid objects has been achieved with the upper part at 300°C and the lower part at 40°C. Further work is being performed in order to increase this temperature differential. [Work supported by NASA.].
Measurement of vibrational relaxation time of oxygen between 475° and 675°K using an acoustic resonant technique
Authors: Feng I-an , Lee Mark C.
Published: October 2005

Vibrational relaxation times of O2-He, O2-CO2, and O2-H2 mixtures have been measured using a resonant chamber method between 475° and 675°K. Data for pure O2 were obtained by extrapolating that of mixtures of zero impurity concentrations. Our data agree with previous acoustic results at 473° and 573°K and shock tube results at 700°K. The temperature dependence of the vibrational relaxation time for pure O2 was compared to theories of Landau-Teller, SSH, and Parker. The simple Landau-Teller theory has shown better agreements with experimental data than that of SSH and Parker's for the case of O2-O2, O2-He, and O2-H2 collisions. [Work supported by NASA.]
Space Shuttle Payload Bay acoustics
Authors: Cho Alfred C.
Published: October 2005

The successful first flight of the Space Shuttle leads to the next important task of carrying payloads safely into orbit. Seven microphones, four internal and three external, were set up to record acoustic noise in the Orbiter Payload Bay. These microphones recorded data for a short duration firing of the Space Shuttle Main Engines (SSME) only, without the Solid Rocket Boosters (SRB). The same microphones then recorded the space flight data that included the firing of both the SSME's and SRB's. These data will be compared with the NASA requirement and analytical prediction. The original assumptions and procedure to predict the internal noise of the Orbiter Payload Bay will also be reviewed.
Automation of vibroacoustic data bank for random vibration criteria development
Authors: Ferebee R. C.
Published: October 2005

A computerized data bank system has been developed for utilization of large amounts of vibration and acoustic data to formulate component random vibration design and test criteria. This system consists of a computer, graphics tablet, and a dry-silver hard copier which are all desktop-type hardware and occupy minimal space. Currently, the data bank contains data from the Saturn V and Titan III flight and static test programs. The vibration and acoustic data are stored in the form of power spectral density and one-third octave band plots over the frequency range from 20 to 2000 Hz. The digitized data were statistically analyzed and the resulting 97.5% probability levels were stored on tape along with the appropriate structural parameters. Standard extrapolation procedures were programmed for prediction of component random vibration test criteria for new launch vehicle and payload configurations. This automated vibroacoustic data bank system greatly enhances the speed and accuracy of formulating vibration test criteria.
Tympanic and extratympanic sound transmission in the leopard frog, Rana pipiens
Authors: Wilczynski Walter , Resler Carl , Capranica Robert R.
Published: October 2005

The relative efficiency of sound transmission to the inner ear of the leopard frog by tympanic vibration and by extratympanic stimulation (presumably via tissue conduction) was investigated by recording the thresholds of eighth nerve auditory fibers at various frequencies within their excitatory tuning curves. The animals were placed on a vibration-isolating table. The eighth cranial nerve was exposed through the roof of the mouth, and a clay cap, molded to mimic the mouth spaces into which the eustachian tubes open, was inserted and sealed with silicon grease, leaving the surgical exposure accessible. An earphone was sealed around one tympanum; the contralateral tympanum and external nares were covered with grease. A loudspeaker was placed 0.8 m from the frog for free-field stimulation. Thresholds of single eighth nerve fibers to sound presented alternately through the earphone and through the loudspeaker were compared. For frequencies below 0.9 kHz, thresholds for the two modes of stimulation were comparable, and generally within 5 dB. For higher frequencies, threshold separation was greater: at 1.7–2.0 kHz, thresholds to sounds presented via the speaker were 15–20 dB higher than those presented through the earphone. These results suggest that at low frequencies the frog's inner ear can be stimulated by both tympanic vibration and by a nontympanic mechanism with nearly equal sensitivity. [Supported by NIH 06237 and NSF BNS 7706803.]
Biophysics of underwater hearing in Rana catesbeiana
Authors: Hetherington Thomas E. , Lombard R. Eric
Published: October 2005

A vertical, water-filled steel pipe, 3 m long with 0.63-cm-thick walls and 15-cm internal diameter was used to determine the biophysical basis of underwater hearing sensitivity in Rana catesbeiana. A speaker inside the base produced standing waves. Pressure and particle motion were measured with a hydrophone and geophone, respectively, and were 90° out of phase along the length of the tube. Microphonic responses were recorded from the inner ear of frogs lowered through pressure and particle motion maxima and minima. The air-filled lungs of whole frogs produced distortions of the sound field. Preparations of heads with only an air-filled middle ear produced little distortion and showed clear pressure tracking at sound intensities 10–20 dB above hearing thresholds from 0.2 to 3.0 kHz. Filling the middle ear with water decreased or abolished microphonic responses. Severing the stapes reduced responses except at certain frequencies below about 1 kHz which varied with body size and likely represent resonant frequencies of the middle ear cavity. We conclude that Rana catesbeiana responds to underwater sound pressure from about 0.2 to 3.0 kHz with the middle ear cavity responsible for pressure transduction. [Work supported by NSF and NIH.]
Efferent desensitization of the responses of turtle single auditory nerve fibers
Authors: Art J. J. , Crawford A. C. , Fettiplace R. , Fuchs P. A.
Published: October 2005

Extracellular recordings were made from single auditory afferents and frequency-threshold curves determined in the isolated half-head of Pseudemys scripta. Constant current shocks, 20–500 μA, in trains at 250 s1, delivered at the junction between the anterior and posterior roots of the statoacoustic nerve, resulted in a prolonged elevation of the thresholds to pure tones, and a broadening of the frequency-threshold curves of the auditory afferents. As an example, in one sharply tuned afferent, a threshold elevation of 41 dB at the characteristic frequency (CF, 700 Hz) was accompanied by a reduction in Q10 dB from 4.7 to 0.9. The extent of desensitization increased steeply with number of shocks, and a train of seven shocks could elevate the threshold at the CF by 80 dB. The desensitization could be demonstrated in a majority of recordings, and observed in the absence of antidromic firing of the afferent. We suggest that a component of this efferent effect may result from a detuning of the hair cell's electrical filter [A. C. Crawford and R. Fettiplace, J. Physiol. 312, 377–412 (1981)].
Orientation signals and responses of inferior collicular units to acoustic stimuli in certain FM and CF-FM paleotropical bats
Authors: Jen Philip H.-S. , Suthers Roderick A.
Published: October 2005

The echolocation system of six species of paleotropical bats was studied by recording their orientation signals and studying the electrophysiological properties of their inferior colliculus. The FM hats use short signals with frequency sweeping downward and the CF-FM bats use signals consisting of a constant frequency followed with a brief downward frequency sweep. Most collicular units discharged either tonically or phasically with peak latency ranging from 3.5 to 49.5 ms. Their threshold curves were triangular shape with minimum thresholds ranging between 1.3 and 179. Sharply tuned threshold curves with very high Q10dB values were only obtained from collicular units of CF-FM bats. An off response upon cessation of stimulus could be measured when the stimulus frequency was at the predominant CF. Whereas collicular units of FM bats were sensitive throughout the frequency range of their emitted signals, collicular units of the CF-FM bats were much sharply tuned to a narrow band of frequencies near that of the CF component of orientation signals. [Work supported by NSF BNS 79-13968.]
Selectivity of single units in the central auditory system of the leopard frog to AM signals
Authors: Rose Gary , Capranica Robert R.
Published: October 2005

Single units in the auditory midbrain nucleus (torus semicircularis) were recorded in leopard frogs Rana pipiens. Acoustic stimuli consisted of pure tones, sinusoidal amplitude-modulated (AM) tones, or sinusoidal amplitude-modulated white noise. On the basis of iso-intensity curves (sound pressure level is held constant while the rate of amplitude modulation is varied), the temporal selectivity of cells in the torus fall into four categories: Nonselective (response is independent of rate of AM); low-pass (response is greatest to low rates of AM); high-pass (response is greatest to high rates of AM); and tuned (response is best to a particular rate of AM). For both amplitude modulated tones and amplitude modulated noise the predominant response type is the tuned class. By using white noise as the carrier source, spectral factors can be eliminated as a source of tuning so that the selectivity of these cells is due exclusively to the temporal features of the stimulus. Those units which show temporal tuning respond maximally when the degree of modulation is 100%. Thus a “temporal tuning curve” could be constructed by determining, for various rates of AM, the percentage modulation required to give a criterion (threshold) number of spikes. The rate of AM at which this criterion threshold could be reached using the lowest percentage modulation is considered to be the best rate of amplitude modulation for that unit. [Supported by NINCDS grant NS-09244.]
Vertical localization of sonar targets by the echolocating bat, Eptesicus fuscus
Authors: Lawrence Beatrice D. , Simmons James A.
Published: October 2005

Echolocating bats (Eptesicus fuscus) can discriminate between pairs of horizontal rods separated by different vertical angles with an acuity of 3° of arc. When the tragus, a prominent external-ear structure located in front of the pinna and external-ear canal, is deflected, vertical-angle discrimination is very poor. The tragus acts as a reflector for producing secondary echoes in the.external-ear impulse response. Vertical target direction is encoded acoustically by the timing and strength of these secondary reflections within the external ear relative to the sound arriving directly at the external-ear canal. These reflections occur only 10 to 20 μs apart, but previous experiments have established that Eptesicus can perceive an echo's arrival time with an acuity of less than 1 μs and can distinguish as discrete echoes signals that are separated by such small time intervals. It thus appears as though echo timing is involved in perception of target range, shape, horizontal direction, and, now, vertical direction. [Work supported by NSF.]
Misarticulating children's perception of the VOT contrast
Authors: Daniloff Ray , Hoffman Paul , Alfonso Peter , Schuckers Gordon
Published: October 2005

Seven multiple-phoneme misarticulating children (ages 5.6 to 6.6) and seven age-matched normally articulating children labeled a seven-step VOT continuum (/pi/ to /bi/) via a picture pointing task. The normal children identified the first three stimuli as /b/ at greater than chance level (p < 0.01), stimulus 4 was identified at chance level (54% /b/) and stimuli 5–7 were identified as /p/ (p < 0.01). The misarticulating children also identified stimuli 1 through 3 as /b/ at greater than chance level (p < 0.05). However, their phoneme boundary included both stimuli 4 and 5 (55% and 40% /b/). Stimuli 6 and 7 were identified as /p/ (75% and 74% /p/) at greater than chance level. Results suggest that multiply misarticulating children may misperceive the VOT contrast even when voicing is not among their production errors.
Interior and exterior resonances in acoustic scattering by spherical targets
Authors: Gaunaurd G. C. , Tanglis E. , Überall H. , Brill D.
Published: October 2005

Acoustic echoes from elastic objects contain resonance features located at the eigenfrequencies of the (fluid-loaded) object, which are physically explained by the excitation of creeping waves inside the object. Corresponding resonance terms may be separated from the total scattering amplitude, leaving behind an apparently nonresonant background amplitude. We demonstrate this for spherical targets. We subsequently show that for near-impenetrable (quasisoft/rigid) spheres, the background amplitude can be split further into a specularly reflected contribution, plus highly attenuated resonance terms caused by the excitation of exterior (Franz-type} creeping waves. The singularity structure of the scattering function is shown mathematically, using the R matrix formalism [i.e., J. Acoust. Soc. Am. 68, 1850–1857 (1980)] to be that of a meromorphic function without any additional “entire function” (as had been postulated by proponents of the Singularity Expansion Method). [H. Überall is also at the Physics Department, Catholic University of America; additionally supported by ONR, Code 421.]
Auditory versus phonetic accounts of observed confusions between consonant phonemes
Authors: Soli Sigfrid D. , Arabie Phipps
Published: October 2005

The utility of phonetic features versus acoustic properties for describing perceptual relations among speech sounds was evaluated with a multidimensional scaling analysis of Miller and Nicely’s [J. Acoust. Soc. Am. 27, 338–352 (1955)] consonant confusions data. The indscal method and program were employed with the original data log transformed to enhance consistency with the linear indscal model. A four-dimensional solution accounted for 69% of the variance and was best characterized in terms of acoustic properties of the speech signal, viz., temporal relationship of periodicity and burst onset, shape of voiced first formant transition, shape of voiced second formant transition, and amount of initial spectral dispersion, rather than in terms of phonetic features. The amplitude and spectral location of acoustic energy specifying each perceptual dimension were found to determine a dimension’s perceptual effect as the signal was degraded by masking noise and bandpass filtering. Consequently, the perceptual bases of identification confusions between pairs of syllables were characterized in terms of the shared acoustic properties which remained salient in the degraded speech. Implications of these findings for feature-based accounts of perceptual relationships between phonemes are considered.
Comments on ’’Studies on the spatial variation of decaying sound fields’’ [J. Acoust. Soc. Am. 63, 1841–1850 (1978)]
Authors: Bodlund K.
Published: October 2005

A paper written by Thomas W. Bartel and Edward B. Magrab under the title above appeared recently in this journal. Undoubtedly, this paper contains valuable information about the spatial variations of the reverberation time at various room conditions, especially concerning the effects of rotating diffusers. However, the paper also contains a rather unfortunate comparison between some measured standard errors and an expression deduced from a paper by Bodlund [J. Sound Vib. 45, 539–557 (1976)]. The comparison is unfortunate, because the deduction is based on some misinterpretations of the basic ideas in this paper.
Comment on ’’Modification of bubble oscillations by nearby objects’’ [J. Acoust. Soc. Am. 64, 937 (1978)]
Authors: Lippmann B. A.
Published: October 2005

It is shown theoretically that when the damping of a damped harmonic oscillator is changed by a small amount, due to the weak coupling to another system, the fractional change in the oscillation frequency is much less than the change in the damping rate.
A model for the fatigue in elastic materials with frequency independent Q
Authors: Caputo Michele
Published: October 2005

The phenomenon of the fatigue in elastic materials is represented by introducing a derivative of real order in the stress–strain relation. It is found that this phenomenon occurs when aγ/ηD (Q is the specific dissipation, η the elastic parameter, ? the yield stress, D the maximum amplitude of the cyclic strain applied with period 4a) is near the critical value 1+0.113/Q. This model allows also to estimate the number of cycles which would give the fatique as function of the maximum strain applied and of its frequency.
Discrimination of uniform spectrum pulse sequences
Authors: Pollack Irwin
Published: October 2005

Random polarity-modulated sequences were produced with a uniform short-term spectrum over defined sampling intervals by a method described by Pierce, Lipes, and Cheetham [J. Acoust. Soc. Am. 61, 1609–1621 (1977)]. These are identified as PLC sequences. By contast, unconstrained random polarity-modulated pulse trains with a constant interpulse interval may depart from a short-term uniform spectrum. It is shown that listeners can clearly discriminate between PLC sequences and unconstrained random sequences, and can discriminate among different PLC sequences. This discrimination is more nearly related to the statistical redundancy of the PLC sequences than to their run-length distribution. Such discrimination is relatively resistant to moderate degrees of temporal jitter and is obtained with other forms of information coding. Discrimination of PLC sequences is presumably based upon phase information.
The development of middle-ear admittance in the hamster
Authors: Relkin Evan M. , Saunders James C. , Konkle Dan F.
Published: October 2005

A high-frequency admittance meter was developed and used to study the maturation of physiological function in the middle ear of neonatal golden hamsters (Mesocricetus auratus). The middle-ear input admittance in the frequency range of 0.8–1.8 kHz was measured in animals ranging in age from 6 to 69 days postpartum. Admittance magnitude was found to increase steadily with age, beginning on day 16, to asymptotic values at each test frequency. There were no obvious differences in admittance growth rates within the range of frequencies tested. However, an analysis of the slopes of the admittance magnitude frequency response curves revealed an increase from 4.6 dB/octave for animals 25 days old or younger, to 6.3 dB/octave for all older animals. This difference between younger and older subjects indicates that the development of the middle ear in the golden hamster is more complex than a simple increase in pure compliance.
A sonar target recognition experiment
Authors: Chestnut Paul , Landsman Helen , Floyd Robert W.
Published: October 2005

This paper presents results of an experiment to determine the feasibility of an active sonar target recognition system. Echo data were obtained from 16 targets of maximum dimension 12 in., submerged in a salt water pool. The target frequency responses in the 15–45-kHz band were used to characterize the targets. The information in the frequency response was extracted in two ways: (1) by calculating the energy in a bank of filters, and (2) by modeling the frequency response as an all-pole filter. Pattern recognition techniques were applied to define and test the two recognition methods. The results show that target recognition is feasible with either of the methods tested. One hundred percent correct recognition is achieved with 15 parameters when no noise is added to the test echoes. If white noise is added to the test echoes, accuracy is well above 90%, provided the signal-to-noise ratio is at least 5 dB.
Synthetic aperture sonar in turbulent media
Authors: Ikeda Osamu , Sato Takuso , Ohshima Hajime
Published: October 2005

A method of synthetic aperture sonar imaging that is effective even in turbulent media is proposed. Signals received at a fixed point on a scanning plane are used as reference signals, and the averaging effect is applied in the process of aperture synthesis to obtain stable images within the same scanning time as conventional methods. The principle and some considerations about the quality of the obtained images are shown, and typical examples derived by computer simulation are given. The results show the effectiveness of the method, and suggest that temporal and spatial correlation lengths of turbulence are the principal factors that dominate the effectiveness.
Acoustic variability due to layered finestructure in the Arctic
Authors: Schulkin M. , Garrison G. R. , Wen T.
Published: October 2005

Acoustic transmission measurements, in the frequency range of 10–60 kHz, have been carried out in the presence of layered, thermal finestructure under an arctic ice island. The term ’’layered finestructure’’ refers to relatively stable, slowly changing thermal layers in the ocean that have a vertical scale of about a meter to tens of meters. Their horizontal extent may be 10–100 times larger. In these measurements, acoustic transmission is strongly affected by the presence, near the transmitter, of a layer or layers with a sound-speed maximum. In the literature these warm layers are sometimes called ’’antiwaveguide’’ or ’’barrier’’ layers. Three types of space–time variability have been found in the records of received intensity versus depth: (1) a small random variability observed at relatively steep transmission angles, (2) a frequency-independent variability which can be related to convergence/divergence of rays in the refraction fields of the layers, and (3) a frequency-dependent variability which seems to arise from the interference between direct rays and those sharply refracted by a layer. A spectral analysis of the interference region confirms that the spatial wavelength in depth is inversely proportional to the acoustic frequency.
Stress wave propagation in bilayered media
Authors: Nayfeh Adnan H.
Published: October 2005

Integral transform techniques are utilized in order to analyze the propagation of spherical waves in bispherical elastic media. A typical model consists of a cavity of radius r0 located at the center of a spherical material (medium 1) which in turn is embedded in an infinite medium of different properties (medium 2). The inner surface of the cavity is loaded with a time dependent explosionlike pressure. The resulting transformed stresses and displacements cannot be inverted to give exact analytic solutions. Exact solutions are only possible to obtain for the special case of a single material and also for the arrival time (wave-front) regions. Solutions of the general bispherical model are obtained by inverting the transforms numerically. It is demonstrated that the maximum stress attained in the outer material is independent of the interface location r1. It is also demonstrated that the maximum stress attained in the inner medium as well as the entire time history of the stress in both materials depend upon r1. The wave-front analysis results are found to form a skeleton of the general solutions which well predict their maximum stresses and their arrival times.
Comparison of the spectra of the cochlear microphonic and of the sound-elicited electrical impedance changes measured in scala media of the guinea pig
Authors: Hubbard Allyn E. , Geisler C. Daniel , Mountain David C.
Published: October 2005

The harmonic structure of the cochlear microphonic (CM) and that of a sound-elicited signal which we have considered as an (apparent) changing resistance (CR) were simultaneously determined in scala media of the first turn of the guinea pig cochlea. We analyzed our data in the context of the Davis variable resistance hair-cell model (1965), which predicts CM and CR to be proportional to each other. But, plotted as functions of the sound-pressure level, CM and CR were found to have qualitatively similar but quantitatively disproportionate spectra. The preparations with the highest endolymphatic potential showed the least correspondence between the spectra of the two measured quantities. The phase angles of the fundamental components in CM and CR were equal within approximately 10°, but the phase of the even harmonics of the two independent measures commonly differed by approximately 180° at lower SPLs. Although most data were collected using 160-Hz tonal stimulation, tones with frequencies up to 1280 Hz produced qualitatively similar results. The CM and the CR both varied slightly with the level of the alternating current used to probe the CR. Considered on a quantitative basis, consistent with the accuracy of our measurements, any model which reduces to a fixed source, a fixed resistance, and a single linear, time-varying resistance cannot mimic the most significant, commonly found aspects of our CM and CR data. An alternate model incorporating a nonlinear, time-invariant resistance is able to account for some of the data. The output of the model is correctly considered a (time) changing resistance, or apparent changing resistance; but the model demonstrates that similar experimental results are not necessarily evidence for a time-varying resistor as originally proposed by Davis.
Maximum likelihood estimation of the position of a radiating source in a waveguide
Authors: Hinich Melvin J.
Published: October 2005

An array of sensors is receiving radiation from a source of interest. The source and the array are in a one-or two-dimensional waveguide. The maximum-likelihood estimators of the coordinates of the source are analysed under the assumptions that the noise field is Gaussian. The Cramer–Rao lower bound is of the order of the number of modes which define the source excitation function. The results show that the accuracy of the maximum likelihood estimator of source depth using a vertical array in a infinite horizontal waveguide (such as the ocean) is limited by the number of modes detected by the array, regardless of the array size.
Controlled impact of a finite elastic circular rod on an isotropic, elastic half-space
Authors: Solecki R.
Published: October 2005

The wave propagation in an elastic circular rod following its impact on elastic half-space is investigated until the instant of separation. The motion of the far end of the rod is assumed to be controlled during the whole process. An approximated response of the half-space is used to calculate resulting deflections and stresses at the interface. These quantities are compared with the corresponding quantities due to the controlled impact on a rigid half-space. It is seen that the flexibility of the half-space has a moderating influence on both the displacements and stresses.
Axisymmetric parametric radiation—A weak interaction model
Authors: Fenlon Francis H. , McKendree Francis S.
Published: October 2005

In this paper the difference-frequency field of a a parametric acoustic radiator is approximated via a weak finite-amplitude solution of the second-order nonlinear paraxial wave equation (i.e., the nonlinear optical analog established by E. A. Zabolotskaya and R. V. Khokhlov [Sov. Phys.–Acoust. 15, 35–40 (1969)]) obtained by expressing the primary waves of an axisymmetrically excited bifrequency piston projector in terms of a weighted sum of Gauss–Laguerre eigenmodes. By relating the fundamental (i.e., Gaussian) mode in the farfield of the projector to those of equivalent ’’Bessel beams’’ a closed-form expression for the difference-frequency field is thus obtained as a function of range. Following a review of the solution’s phenomenological properties comparisons are made of predicted results and experimental data reported in the literature.
Low-frequency expansions for acoustic wave scattering using Waterman’s T-matrix method
Authors: Varadan Vasundara V. , Varadan Vijay K.
Published: October 2005

Analytical expressions are derived for the T-matrix elements of cylindrical and spheroidal inclusions and cavities as an expansion in powers of the nondimensional wavenumber ka. For plane monochromatic acoustic wave incidence, analytical expressions are presented for the farfield scattered amplitude. These expressions are compared with existing, exact results using Mathieu functions and spheroidal functions. The agreement is shown to be exact to any given order in ka, giving a strong indication that at least in the farfield the T matrix leads to the proper asymptotic expansion in ka.
Impedance matching by the combined effects of the outer and middle ear
Authors: Killion Mead C. , Dallos Peter
Published: October 2005

When the impedance mismatch between air and the oval window is computed by considering the latter as a small piston in a baffle, and taking the appropriate source impedance into account, it can be shown that the mismatch is frequency dependent and may be greater than 50 dB at 100 Hz. The middle ear transformer by itself is inadequate to compensate for the loss of transmission due to the mismatch. Only at the frequency of the outer ear resonance does the combined action of the outer ear and the middle ear produce an estimated gain that roughly compensates for the loss of energy at the interface. Detailed computations are shown for cats, and some results applicable to the human ear are also included.
The Mellin transforms and constant-Q spectral analysis
Authors: Gambardella G.
Published: October 2005

It has been shown recently that constant-Q spectral analysis constitutes one means for implementing a Fourier-Mellin transform which is relevant in acoustical signal processing. This letter points out a further connection between constant-Q spectral analysis and the Mellin transform: The latter is shown to be the basis for inverting the integral transforms representing both the ’’short-time’’ and the ’’average power spectrum’’ resulting from any constant-Q spectral analysis.
Shading of acoustic and antenna arrays
Authors: Wilson G. L.
Published: October 2005

The criteria used in the Lagrange multiplier technique for obtaining shading coefficients for an array are compared with those used in the linear programming technique and with more recent nonlinear goal programming techniques.
Does mode coupling affect multipath time stretching?
Authors: Woodsum Harvey C. , Kaufman Charles
Published: October 2005

An analysis of guided wave propagation based on the assumption that the normal modes of propagation are uncoupled leads one to conclude that multipath time strectching in underwater acoustic communications is proportional to the first power of propagation distance. Based on an optical analogy and recent theoretical work dealing with normal mode coupling, we suggest that, under certain circumstances, the multipath time stretching is considerably less severe due to the effect of mode coupling.
Some comments on the literature of propagation near boundaries of finite acoustical impedance
Authors: Daigle G. A. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

There are numerous minor errors in the literature on sound propagation near boundaries of finite impedance. These occur mainly because authors have variously used both possible sign conventions for time dependence, viz. eiωt and e−iωt. This paper lists the relevant mathematical consequences of each sign convention and how authors have divided between them. Errata are noted in several of the cited papers.
Temporal summation of pulsate brain stimulation in normal and deafened cats
Authors: Gerken George M.
Published: October 2005

Behaviorally measured, electrical-stimulation thresholds were obtained from 11 electrodes permanently positioned in the auditory system and other brain loci. Number of pulses and interpulse intervals were varied to determine how detection thresholds were affected by stimulation parameters. Detection thresholds generally decreased with increased number of pulses and with shorter interpulse intervals. A method is presented to describe the parametric threshold data for each electrode in terms of three constants: a single-pulse threshold which characterizes the sensitivity of the placement; a time constant of temporal summation; and a compression factor which describes the range of threshold variation. For three placements in the vicinity of cochlear nucleus, bilateral cochlear destruction permanently altered parametric thresholds. In particular, single-pulse threshold was lowered by 9.2 dB; time constant of temporal summation was reduced by a factor of 100; and the compression factor was increased. Classic strength-duration time constants were determined using behavioral methods and were shown to be equal in magnitude to the greatly reduced time constants for temporal summation in the deafened animals. This implies that capacity for temporal integration may be substantially reduced or lost in at least the lower level of the auditory system following deafness.
Suppression of aerodynamically induced cavity pressure oscillations
Authors: Shaw L. L.
Published: October 2005

A flight test program was performed to gain further insight into the phenomenon of flow-induced pressure oscillations in cavities and to evaluate the effectiveness of various suppressure concepts. The cavity tested was rectangular with dimensions of 17 in. long, 8.5 in. deep, and 8.75 in. wide. It was instrumented with microphones, static pressure ports, and a thermocouple. The flight speeds ranged from Mach number 0.6 to 1.3 at pressure altitudes of 3000, 20 000, and 30 000 ft. The suppression devices tested included leading edge spoilers and deflectors and trailing edge ramps and deflectors. Several combinations of these were tested. The results indicate that the flow-induced pressure oscillations in a cavity, can be significantly reduced with leading edge spoilers in conjunction with a trailing edge ramp. A 20-dB reduction was achieved for the predominant modal frequency. Other combinations of the suppression devices afforded some reduction, but the spoiler–ramp combination proved most effective.