bluuebunny/crossref_metadata_2025 huggingface dataset:
Histological evaluation of damage in cat cochleas used for measurement of basilar membrane mechanics
Authors: Leonard D. G. B. , Khanna S. M.
Published: October 2005

Cochleas utilized in basilar membrane vibration measurements were examined histologically using an epon-embedded surface preparation technique. The amount of damage observed at both the apical and basal ends of the cochleas was variable. The apical damage was probably caused by large, low-frequency movements of the basilar membrane. The basal damage was due to trauma produced directly by the surgical and experimental procedure. The sharpness of tuning observed in the basilar membrane frequency response was found to be inversely related to the extent of histological damage.
Infrasonic ambient noise measurements in deep Atlantic water
Authors: Talpey T. E. , Worley R. D.
Published: October 2005

Measurements of ocean ambient noise were made at three intervals during a period of a year and a half using a hydrophone bottomed at 3500 m depth on the slope south of Bermuda, about 2300 m below the sound channel axis. Spectra were obtained for the frequency band 0.1–12.5 Hz. The results were compared with those of other experimenters and were found to be in general agreement. Correlation coefficients of spectrum levels at selected frequencies with concurrent wind speeds were calculated.
Perception of consonants in reverberation by native and non-native listeners
Authors: Nábělek Anna K. , Donahue Amy M.
Published: October 2005

Speech perception in reverberation was compared for native English speaking and non-native listeners. The Modified Rhyme Test was recorded with reverberation times (T) of 0.4, 0.8, and1.2 s. Testing was monaural. The mean word identification scores without reverberation were similar for both groups. With T=0.8 and 1.2 s, non-native listeners scored 10% lower than the native listeners. These results indicate that non-native listeners who understand English very well in the absence of reverberation might have difficulty understanding speech in the presence of even moderate reverberation.
Temporal gap resolution in narrow-band noises with center frequencies from 6000–14000 Hz
Authors: Fitzgibbons Peter J.
Published: October 2005

Temporal resolution was examined in normal-hearing subjects using a broadband noise and five narrow-band noises with center frequencies ( fc) spaced 2 kHz apart between 6 and 14 kHz. Bandwidths of the narrow-band signals were equal to 0.16 fc, and broadband noise maskers with spectral notches were used to restrict the listening bands. Subjects used a Békésy procedure to track the minimum signal level required to keep a periodic temporal gap of fixed duration at threshold. Gap durations from 25 ms to the smallest trackable value were tested with each signal to generate performance curves, which showed the relationship betwen gap resolution and signal level in the low-to-moderate intensity range. Results showed that gap resolution improved progressively with increased signal level to about 35 dB SL, where minimum gap thresholds of about 3 ms were observed for all signals. These results, when combined with previous low-frequency data, indicate that gap threshold decreases systematically with increased signal frequency to about 5 kHz, and asymptotes at 2–3 ms for higher frequencies. In the context of functional models, the frequency effect is qualitatively consistent with the notion that both the auditory filter and a sensory integrator operate in series to govern temporal resolution in audition.
Infant discrimination of two- and five-formant voiced stop consonants differing in place of articulation
Authors: Walley Amanda C. , Pisoni David B. , Aslin Richard N.
Published: October 2005

According to recent theoretical accounts of place of articulation perception, global, invariant properties of the stop CV syllable onset spectrum serve as primary, innate cues to place of articulation, whereas contextually variable formant transitions constitute secondary, learned cues. By this view, one might expect that young infants would find the discrimination of place of articulation contrasts signaled by formant transition differences more difficult than those cued by gross spectral differences. Using an operant head-turning paradigm, we found that 6-month-old infants were able to discriminate two-formant stimuli contrasting in place of articulation as well as they did five-formant + burst stimuli. Apparently, neither the global properties of the onset spectrum nor simply the additional acoustic information contained in the five-formant + burst stimuli afford the infant any advantage in the discrimination task. Rather, formant transition information provides a sufficient basis for discriminating place of articulation differences.
Some acoustical measurements on the Chinese musical instrument P’i-P’a
Authors: Feng Shih-yu
Published: October 2005

Sinusoidally driven response curves and holographic time-average vibration mode patterns were obtained for the Chinese musical instrument P’i-P’a. It was found that the frequency of the top plate resonances lie at the higher end of the range of this instrument and therefore the plate resonances have the effect of strengthening the harmonic components of the most frequently played mid-range notes. Calculation predicted a Helmholtz air resonance at 139 Hz, but experimentally the air resonance was not found, indicating a very weak air peak.
Frequency specificity of human auditory brainstem responses as revealed by pure-tone masking profiles
Authors: Folsom Richard C.
Published: October 2005

The frequency specificity of the auditory brainstem response (ABR) was examined by means of pure-tone masking profiles using click, 4000-Hz, and 1000-Hz filtered-click stimuli. Simultaneous pure-tone maskers were presented at one-half octave intervals around stimulus center frequency. Masking profiles at two intensities (60 and 40 dB SL) were obtained by measuring both latency and amplitude shifts in wave V as a result of the discrete-frequency maskers. Both latency and amplitude analyses showed masking profiles at 40 dB SL that were narrow and centered around stimulus frequency, whereas profiles at 60 dB SL showed high-frequency spread of the cochlear excitation area.
Frequency effects in backward masking
Authors: Dolan Thomas G. , Small Arnold M.
Published: October 2005

Frequency effects in auditory backward masking were examined by psychophysically determining the thresholds of 0.5-, 1-, 3-, 5-, and 7-kHz sinusoidal probes followed by a broadband noise masker. For each probe frequency, backward masking decreased approximately exponentially as the temporal interval between the probe and masker was increased. The rate of this exponential decay increased with increasing probe frequency. This latter result is consistent with Duifhuis’ [J. Acoust. Soc. Am. 54, 1471–1488 (1973)] theory which attributes backward masking to the temporal overlap of cochlear responses to the probe and masker.
Temporal integration of forward masking in listeners having sensorineural hearing loss
Authors: Kidd Gerald , Mason Christine R. , Feth Lawrence L.
Published: October 2005

Findings are described from three experiments that were designed to contrast estimates of auditory time and frequency analysis in highly practiced, young adult subjects having sensorineural hearing loss of cochlear origin with subjects having normal hearing. In one experiment, pure-tone detection threshold was measured for two durations of tones. For the hearing-impaired subjects, smaller differences were found between thresholds for the two durations of tones than were found for the normally hearing subjects at test frequencies where the sensitivity loss was greatest. In a subsequent forward masking experiment, masked thresholds were obtained at 3 kHz as a function of masker level at several masker durations. The results indicated that, for the range of values tested, masked probe thresholds changed less as a function of masker duration for the hearing-impaired subjects than for normally hearing subjects. However, forward masking grew as a function of masker level more steeply for the hearing-impaired listeners than for the normally hearing listeners. We believe that this result indicates abnormal temporal processing of sequential sounds. In a third experiment, psychophysical tuning curves were measured in a forward masking procedure for two maskers that differed in duration by approximately an order of magnitude. Again, the hearing-impaired subjects demonstrated less change in forward masking as a function of masker duration than normally hearing subjects. Further, the sharpness of the tuning curves from the hearing-impaired listeners was markedly reduced as compared to normal. It is believed that the results reflect a disruption of the normal temporal and spectral representation of sounds in the hearing-impaired subjects.
Acoustic scattering by baffled membranes
Authors: Kriegsmann Gregory A. , Norris Andrew , Reiss Edward L.
Published: October 2005

A flexible membrane is set in an infinite plane baffle. The plane separates an acoustic field from a vacuum. A time harmonic wave is incident from the fluid on the membrane. When the frequency of the incident wave is not close to an in-vacuo resonant frequency of the membrane, the reaction of the fluid on the membrane is small. However, near a resonant frequency the fluid–membrane coupling is significant. We use the method of matched asymptotic expansions to obtain an asymptotic expansion of the scattered field. It is uniformly valid in the incident frequency. The expansion parameter ε≪1 is the ratio of the fluid and membrane densities. The outer expansion, valid away from resonance, is O(ε). The inner expansion, valid near resonance, is of order unity. The fluid loading is shown to have the effect of decreasing the resonant frequencies from those of the in-vacuo membrane. Simple and double resonant frequencies are analyzed. However, the method is applicable to higher order resonant frequencies. Finally, the method is applied to normal incidence of a plane wave on a circular membrane.
Acoustic radiation from fluid-loaded infinite circular cylinders with doubly periodic ring supports
Authors: Burroughs Courtney B.
Published: October 2005

Analytic expressions are derived for the farfield acoustic radiation from a point-driven, fluid-loaded circular cylindrical shell reinforced with doubly periodic ring supports. The ring supports interact with the cylindrical shell only through normal forces. The model includes the effects of fluid loading and interactions between supports. Predictions are compared to measured farfield acoustic radiation data taken on a finite circular cylindrical shell with doubly periodic ring supports. Characteristics of the acoustic radiation are examined by example and some physical interpretation of significant features are offered.
Nearfield of a large acoustic transducer. Part III: General results
Authors: Garrett Greer S. , Tjo/tta Jacqueline Naze , Tjo/tta Sigve
Published: October 2005

The theory presented in two previous papers [Part I, J. Acoust. Soc. Am. 72, 1056–1061 (1982) and Part II, J. Acoust. Soc. Am. 74, 1013–1020 (1983)] is further developed and generalized to the case of no axisymmetry. Emphasis is given to a study of the parametric generated sound. Asymptotic formulas are presented, showing the development of the difference frequency sound from the source (transducer) into the farfield. New numerical results for the axisymmetric case are given for the linear and the parametric field of a source which is not radiating uniformly. New experimental results are reported and compared with the theory.
Oscillation modes in single-step Hartmann–Sprenger tubes
Authors: Kawahashi Masaaki , Bobone Richard , Brocher Eric
Published: October 2005

When a high velocity jet is directed toward the mouth of a tube closed at the downstream end, large, nonlinear flow oscillations may occur within the tube. Shock waves propagate up and down the tube and generate strong heating of the tube walls. The device is called a Hartmann–Sprenger tube (in short, H–S tube). It has been proposed by several investigators to strengthen the shock waves and consequently the heating effects by tapering the tube. Conical and multistepped configurations have been investigated, but also tubes having a sudden area contraction (single step). This latter geometry produces remarkable pressure and thermal heating amplification compared to a constant area tube. The paper presents theoretical and experimental results obtained for the single-step H–S tube. It is shown that several oscillation modes can exist. These are separated by intervals of instability. The influence of geometrical parameters (upstream to downstream cavity diameter and length ratios) and of jet Mach number on oscillation mode is investigated.
Speech coding in the auditory nerve: I. Vowel-like sounds
Authors: Delgutte Bertrand , Kiang Nelson Y. S.
Published: October 2005

Discharge patterns of auditory-nerve fibers in anesthetized cats were recorded in response to a set of nine steady-state, two-formant vowels presented at 60 and 75 dB SPL. The largest components in the discrete Fourier transforms of period histograms were almost always harmonics of the vowel fundamental frequency that were close to one of the formant frequencies, the fundamental frequency or the fiber characteristic frequency (CF). For any fiber, the position of its CF relative to the formant frequencies (F1 and F2) appears to determine which of these components dominates the response. Specifically, the response characteristics of the tonotopically arranged array of fibers can be described in terms of five CF regions: (1) a low-CF region below F1 in which the largest response components are the harmonics of the fundamental frequency closest to CF; (2) a region centered around CF = F1 in which the first formant and its harmonics are the largest components; (3) an intermediate region between F1 and F2 with prominent components at both the fiber CF and the fundamental frequency; (4) a region centered around CF = F2 in which harmonics close to the second formant are the largest for frequencies above the fundamental; and (5) a high-CF region in which response spectra tend to show broad, multiple peaks at the formant and fundamental frequencies. These CF regions are related to the phonetic descriptions of vowels. For example, the extent of the low-CF region is largest for ‘‘open’’ vowels (which have a high F1), and the intermediate region is distinct only for ‘‘spread’’ vowels for which F1 and F2 are more than 1.5–2 octaves apart. For all vowels, response activity for the majority of fibers is concentrated near the formant frequencies, in contrast to responses to broadband noise for which components near CF are dominant.
Speech coding in the auditory nerve: II. Processing schemes for vowel-like sounds
Authors: Delgutte Bertrand
Published: October 2005

Several processing schemes by which phonetically important information for vowels can be extracted from responses of auditory-nerve fibers are analyzed. The schemes are based on power spectra of period histograms obtained in response to a set of nine two-formant, steady-state, vowel-like stimuli presented at 60 and 75 dB SPL. One class of ‘‘local filtering’’ schemes, which was originally proposed by Young and Sachs [J. Acoust. Soc. Am. 66, 1381–1403 (1979)], consists of analyzing response patterns by filters centered at the characteristic frequencies (CF) of the fibers, so that a tonotopically arranged measure of synchronized response can be obtained. Various schemes in this class differ in the characteristics of the filter. For a wide range of filter bandwidths, formant frequencies correspond approximately to the CFs for which the response measure is maximal. If in addition, the bandwidths of the analyzing filters are made compatible with psychophysical measures of frequency selectivity, low-frequency harmonics of the stimulus fundamental are resolved in the output profile, so that fundamental frequency can also be estimated. In a second class of processing schemes, a dominant response component is defined for each fiber from a 1/6 octave spectral representation of the response pattern, and the formant frequencies are estimated from the most frequent values of the dominant component in the ensemble of auditory-nerve fibers. The local filtering schemes and the dominant component schemes can be related to ‘‘place’’ and ‘‘periodicity’’ models of auditory processing, respectively.
Response to the Comments of Nyborg and Rooney [J. Acoust. Soc. Am. 7
5, 263–264 (1984)]
Authors: Chu Boa-Teh , Apfel Robert E.
Published: October 2005

We emphasize the concept that the radiation force on a target produced by a confined beam of sound is given by that in an open vessel plus an acoustically induced hydrostatic pressure. The possibility of obtaining a continuum of values for the measured radiation force on a perfectly absorbing target is also analyzed.
On the role of the amplitude envelope for the perception of [b] and [w]
Authors: Shinn Phil , Blumstein Sheila E.
Published: October 2005

This study investigated the role of the amplitude envelope in the vicinity of consonantal release in the perception of the stop–glide contrast. Three sets of acoustic [b-w] continua, each in the vowel environments [a] and [i], were synthesized using parameters derived from natural speech. In the first set, amplitude, formant frequency, and duration characteristics were interpolated between exemplar stop and glide endpoints. In the second set, formant frequency and duration characteristics were interpolated, but all stimuli were given a stop amplitude envelope. The third set was like the second, except that all stimuli were given a glide amplitude envelope. Subjects were given both forced-choice and free-identification tasks. The results of the forced-choice task indicated that amplitude cues were able to override transition slope, duration, and formant frequency cues in the perception of the stop–glide contrast. However, results from the free-identification task showed that, although presence of a stop amplitude envelope turned all stimuli otherwise labeled as glides to stops, the presence of a glide amplitude envelope changed stimuli labeled otherwise as stops to fricatives rather than to glides. These results support the view that the amplitude envelope in the vicinity of the consonantal release is a critical acoustic property for the continuant/noncontinuant contrast. The results are discussed in relation to a theory of acoustic invariance.
Effect of flow disturbance on ultrasonic backscatter from blood
Authors: Shung K. K. , Yuan Y. W. , Fei D. Y. , Tarbell J. M.
Published: October 2005

Due to the better resolution and performance provided by the new generation of real-time high resolution ultrasonic scanners, blood now becomes a tissue which can also be visualized ultrasonically. There is strong experimental evidence indicating that the echogenicity of blood is increased as a result of erythrocyte aggregation. In this paper, we will show that flow disturbance may also play a significant role in influencing blood ultrasonic backscatter or echogenicity. Our results indicate that the introduction of turbulent flow can cause ultrasonic backscatter from erythrocyte suspensions to increase appreciably for hematocrits greater than 10%. We will also show that this increase may be correlated to the turbulent intensity. Moreover, the scattering peak is observed to shift to lower hematocrits when turbulence is eliminated. Experimental results obtained for uniform flow are in excellent agreement with theoretical models for small spherical scatterers which predict a scattering maximum at a hematocrit of 13%.
Cepstrum analysis of surface waves in acoustic signature inspection of railroad wheels
Authors: Fahmy Mahmoud N. , Finch Robert D.
Published: October 2005

Surface waves are produced by hammer impact on the rim of a railroad wheel. They travel around the wheel tread making one complete traverse of the circumference every millisecond. If a receiver is located close to the impact point the signal shows a series of arrivals at millisecond intervals. If a crack is present in the surface, there will be an extra impulse received in the first millisecond interval. Both contacting accelerometers and noncontacting microphones can be used to detect the signals. If the signals are digitized and processed in time, frequency, and quefrency domains, the presence of the crack can be seen most clearly by liftering the cepstrum to remove all but the initial reflection from the crack.
Silicon-dioxide electret transducer
Authors: Hohm D. , Gerhard-Multhaupt R.
Published: October 2005

A new type of electret transducer based on the use of an SiO2 backplate electret is presented. Frequency-response measurements on a prototype device demonstrate the feasibility of the design. Possible improvements and the main advantages of the new transducer principle are discussed.
Imaging through an inhomogeneous layer by least-mean-square error fitting
Authors: Hirama Makoto , Sato Takuso
Published: October 2005

A new active ultrasonic imaging method through an inhomogeneous layer is proposed. It has the special feature that its effectiveness does not depend on the class of the objects to be imaged. In this method, first, a set of data is acquired by repeating transmission and reception for all possible combinations of pairs of transducers on the array, then the spatial frequency components of the object and the structure of the inhomogeneous layer are estimated from these data by means of least-mean-square error fitting. Since the data have redundancy for the parameters to be estimated, this process gives an optimum and stable estimation algorithm even when measurement errors and noise are included. The image is reconstructed from the estimated spatial frequency components through inverse Fourier transform. The effectiveness of this method is ensured by several numerical analyses and experiments.
Identification and discrimination of rise time: Is it categorical or noncategorical?
Authors: Kewley-Port Diane , Pisoni David B.
Published: October 2005

Previous studies have reported that rise time of sawtooth waveforms may be discriminated in either a categorical-like manner under some experimental conditions or according to Weber’s law under other conditions. In the present experiments, rise time discrimination was examined with two experimental procedures: the traditional labeling and ABX tasks used in speech perception studies and an adaptive tracking procedure used in psychophysical studies. Rise time varied from 0 to 80 ms in 10-ms intervals for sawtooth signals of 1-s duration. Discrimination functions for subjects who simply discriminated the signals on any basis whatsoever as well as functions for subjects who practiced labeling the endpoint stimuli as ‘‘pluck’’ and ‘‘bow’’ before ABX discrimination were not categorical in the ABX task. In the adaptive tracking procedure, the Weber fraction obtained from the jnds of rise time was found to be a constant above 20-ms rise time. The results from the two discrimination paradigms were then compared by predicting a jnd for rise time from the ABX discrimination data by reference to the underlying psychometric function. Using this method of analysis, discrimination results from previous studies were shown to be quite similar to the discrimination results observed in this study. Taken together the results demonstrate clearly that rise time discrimination of sawtooth signals follows predictions derived from Weber’s law.
Detection of frequency and rate modulation by the chinchilla
Authors: Long Glenis R. , Clark William W.
Published: October 2005

Thresholds for detection of frequency modulation were obtained from three chinchillas at seven frequencies between 320 Hz and 12.75 kHz and at three sensation levels (20, 40, 60 dB SL). These were compared with human thresholds at 40 dB SL obtained under the same conditions. Our data show no significant impact of sensation level and confirm Nelson and Kiester’s [J. Acoust. Soc. Am. 64, 114–126 (1978)] report that the chinchilla has much poorer frequency discrimination than man. In an attempt to assess separately the chinchilla’s capacity for temporal coding of frequency, thresholds for detection of a change in the modulation rate of amplitude modulated noise were obtained for nine modulation frequencies between 10 and 320 Hz. The chinchillas needed a larger rate change for detection than most humans but the relative difference was less than that found for frequency modulation detection.
A finite difference solution for the propagation of sound in near sonic flows
Authors: Hariharan S. I. , Lester Harold C.
Published: October 2005

An explicit time/space finite difference procedure is used to model the propagation of sound in a quasi-one-dimensional duct containing high Mach number subsonic flow. Nonlinear acoustic equations are derived by perturbing the time-dependent Euler equations about a steady, compressible mean flow. The governing difference relations are based on a fourth-order, two-step (predictor–corrector) MacCormack scheme. Difference equations for the source and termination boundary conditions are derived from the appropriate characteristic relationships. The solution algorithm functions by switching on a time harmonic source and allowing the difference equations to iterate to a steady state. A significant advantage with this approach is that the nonlinear terms can be retained and evaluated with only modest additional computer cost above that required for a linear model calculation. The principal effect of the nonlinearities was to shift acoustical energy to higher harmonics. With increased source strengths, wave steepening was observed. This phenomenon suggests that the acoustical response may approach a shock behavior at a higher sound pressure level as the throat Mach number approaches unity. Where applicable, comparisons were made with the calculations from a linear finite element algorithm. On a peak level basis, good agreement between the nonlinear finite difference and linear finite element solutions was observed, even though a peak sound pressure level of about 150 dB occurred in the throat region. Nonlinear steady-state waveform solutions are shown to be in excellent agreement with a nonlinear asymptotic theory.
Time spread of acoustic signals reflecting from a fixed rough boundary
Authors: Brill Michael H. , Zabal Xavier , Adams Stanley L.
Published: October 2005

The time spreading of a spherical-wave impulse of acoustic power reflecting from a not-too-rough fixed boundary (such as an ocean bottom) is computed using a simple geometric-acoustic model. In that model, a ray reflects specularly from each boundary facet, and arrives at the receiver if and only if the position and slope of the facet provide the requisite specular path. In this way, the probability of reception of a ray from a particular facet is tied to the slope distribution of the reflecting boundary (assuming the depth is constant). A general expression for time spread is derived, and computed time spreads are presented for particular source/receiver geometries. Appreciable time spreads (up to half a second) are shown for benign ocean-boundary conditions (rms slope ≲tan 15°). Time spreads increase dramatically with rms slope, decrease with increasing range, and increase with increasing depth from source/receiver to the boundary. It is emphasized that, for broadband signals, models must be in three dimensions (as opposed to two) and depart from plane-wave idealizations.
Acoustic scattering by fish—Acoustic models and a two-parameter fit
Authors: Clay C. S. , Heist Barry G.
Published: October 2005

The Rician probability density function (PDF) accurately describes acoustic scattering by individual live fish. A fish scattering model is proposed which contains concentrated scattering components (representing the swim bladder) and distributed scattering components (representing the fish skeletal structure). We associate the gross directional backscattering cross section with the concentrated component. The ratio of these two components, γ, may serve as a means of identifying different fish species and fish behavior from the scattering PDFs. Monte Carlo simulations of a swimming fish using the acoustic fish model give Rician PDFs.
Selective adaptation to linear frequency-modulated sweeps: Evidence for direction-specific FM channels?
Authors: Wakefield Gregory H. , Viemeister Neal F.
Published: October 2005

Psychometric functions were obtained for detection of linear frequency-modulated pure tones which were preceded by either a pure tone or a linear FM pure-tone adaptor. The results of Gardner and Wilson [J. Acoust. Soc. Am. 66, 704–709 (1979)] were generally confirmed: Thresholds were larger by about a factor of 1.7 when the adaptor and test sweeps rose in frequency. This increase in threshold corresponds to a change in performance from 75% to 65% correct. As an alternative to feature-selective channels, we propose that this small effect is due to nonsensory factors, specifically, the use of an adaptor-like reference in the ‘‘adapted’’ condition. Performance similar to that obtained in humans is shown by an ideal receiver that uses an inappropriate reference to match the signal in the detection task.
Comparison of laboratory and field sound insulation measurements of party walls and facade elements
Authors: Taibo Lucía , de Dayan Hilda Glasserman
Published: October 2005

In the present work, eight party walls and facade elements have been measured in laboratory and field conditions. Lab measurements were carried out in a horizontal chamber, with flanking transmission, that basically fulfills the requirements of DIN 52210/2 standard. Field tests were performed in real dwellings, with typical furnishings and linings. The installation of samples was carefully controlled, in order to reproduce similar mountings in both situations. Velocity measurements were made during field tests in order to define the principal paths of sound transmission. Leaks were avoided in each case. The overall variability of tests was determined from the study of random sources of error. For this purpose, two operators made three replications under the same environmental conditions, with the same instrumentation for each measuring sample. To the contrary, both operators did each set of replicates, at long intervals of time with different equipment. Finally, a correlation between lab–field results was found. The fitted straight line shows that field results are systematically lower than lab results, and the resulting differences tend to rise with increasing insulation values.
Uncertainty principle in frequency–time methods
Authors: Tsao Y. H.
Published: October 2005

Stochastic process theory has recently been extended to the nonstationary case and the concepts extended to include the time-varying parameters such as evolutionary spectra. Previous papers have reviewed and concluded that despite the time variation underlined, the evolutionary spectral density function may still be estimated or measured for numerous nonstationary processes. One of the most important aspects of the practical estimates is closely related to their accuracy which is now defined in both the frequency and time dimensions. In this paper the limit of the two resolutions for the common evolutionary spectral estimators is discussed and the obvious trade-off relationship between the two is explained in the context of the popular filter/window techniques. It is found that if the first moment Bg of the filter/window function in time together with the 3-dB cutoff frequency are selected as the uncertainty measures then the product Bg f3/2c would be a dimensionless quantity which purely describes the filter/window qualities. In particular, the product varies very little among nearly all conventional window functions and the average can effectively be regarded as a constant uncertainty product which may prove useful in applied spectral analysis.
Postnatal functional development of the dorsal and posteroventral cochlear nuclei of the cat
Authors: Brugge John F. , O’Connor Thomas A.
Published: October 2005

The postnatal development of firing patterns and response areas was determined for single neurons in the dorsal (DCN) and posteroventral (PVCN) cochlear nuclei of the kitten. Extracellular, single-unit responses to pure-tone stimulation were recorded in ketamine and sodium pentobarbital anesthetized kittens between the ages of 5 and 52 days. Within the first two weeks of postnatal life threshold is high, first-spike latency is long, and maximal discharge rate is low as compared to older kittens and adult cats. Prior to the end of the second postnatal week the tone-evoked temporal discharge patterns that characterize neurons of the DCN and PVCN in the adult cat are routinely recorded. These patterns, which appear within the first 50 ms of tonal stimulation, include the so-called ‘‘primarylike,’’ ‘‘chopper,’’ ‘‘pauser,’’ ‘‘buildup,’’ and ‘‘onset’’ types and their variants. In animals younger than about 10–12 days of age, the driven activity that occurs later than about 50 ms after stimulus onset often is not sustained, but breaks up during the stimulus into bursts that are separated by intervals of about 100–150 ms. Also within the first two weeks of postnatal life, many of the response-area properties of DCN and PVCN neurons are similar to those recorded in adult cats. The excitation and inhibition found within the so-called type II/III, type IV, and type V response areas of the adult occur in this early postnatal period. We conclude that many of the cellular mechanisms that underlie the temporal firing patterns and the organization of the response areas of DCN and PVCN neurons are active in the growing, differentiating cochlear nuclei and that the emergence of these mechanisms does not depend on afferent activity generated in the cochlea and auditory nerve by the animal’s acoustic environment. Furthermore, if temporal firing patterns and response-area profiles remain relatively constant over the life span of the animal, then so must the spatial and temporal relationships of the inputs that produce and maintain them as these neurons, and the circuits of which they are a part, grow in size and complexity.
Stochastic propagation of the mutual coherence function in the deep ocean
Authors: Baer R. N. , Perkins J. S. , Wright E. B. , McCoy J. J.
Published: October 2005

We present a computer-implemented algorithm for underwater acoustic propagation based upon a theoretical formulation which simultaneously incorporates probabilistic random volume scattering and deterministic refraction and diffraction. The model, called the Combined Effects Model, adds the vertical scattering caused by the random inhomogeneities in the ocean to the multipath features produced by the mean sound-speed structure. The analysis is based on the two-point coherence function which describes the acoustic field in terms of position and the direction of energy flux, and as such is directly related to the field as seen by an acoustic array. Basic to the theoretical formulation is a locally quadratic approximation on the index of refraction. Although multipath interference effects (which are apparent when the coherence function is calculated directly from a propagation algorithm) are lost with this assumption, estimates for the output of a vertical array are not significantly affected. The incorporation of random volume scatter with realistic background sound-speed structure results in the distribution of arriving energy being smoothed over vertical arrival angles. This effect depends on the magnitude of the strength of the fluctuating field. The multipath structure can still exist for over 100 km, for signals below a few hundred Hz, in the presence of a typical scattering field or can deteriorate in the first few kilometers in the presence of strong scatter.
Acoustic ray-path fluctuations induced by El Niño
Authors: Lawson L. M. , Palmer D. R.
Published: October 2005

This paper represents a first step in determining the degree to which an El Niño event can be monitored using acoustic tomographic techniques. In tropical waters an acoustic ray entering the near-surface region from below usually is strongly refracted because of the steep gradient in the sound speed and therefore turns over very rapidly. Since the temperature perturbation associated with an El Niño event is restricted to this near-surface region, there has been some concern that ray-path travel-time fluctuations would be too small to be easily detected. In this note we address this concern using data measured during the 1982–1983 event. We conclude that the travel-time fluctuations are large enough to be easily measured for almost all ray-path configurations of interest. We also discuss the direction future efforts might take.
Multiple modal resonances of thin cylindrical shells vibrating in an acoustic medium
Authors: Junger M. C. , Garrelick J. M.
Published: October 2005

Structural modes of a thin cylindrical shell can display as many as three natural frequencies when immersed in an acoustic medium, all lower than the corresponding in vacuo natural frequency. This phenomenon results from the marked peak displayed by the inertial radiation loading of a slender cylindrical shell when the structural wavenumber of a modal configuration lies close to the acoustic wavenumber. This is illustrated for the axisymmetric ‘‘breathing mode’’ in the limiting case of an infinitely periodic cylindrical shell. For the parameters of metal shells in water, three natural frequencies are anticipated for modes whose axial wavelength exceeds the radius by at least one order of magnitude. For submerged shells of less stiff material or smaller modal wavelength-to-radius ratio, one or two natural frequencies are predicted.
Reflection of parametric radiation from a finite planar target
Authors: Garrett Greer S. , Tjo/tta Jacqueline Naze , Rolleigh Richard L. , Tjo/tta Sigve
Published: October 2005

Results are reported of an investigation of the reflection of parametric radiation from a finite planar target. The interference of the difference frequency sound generated after reflection with the reflected difference frequency sound is considered. Amplitude and phase were measured before and after reflection from a polyfoam target. Target size ranged from slightly larger than the beamwidth to smaller than the beamwidth. The results are compared with calculations based on equations describing the linear radiation and the parametric radiation. These equations are derived using the parabolic approximation.
Broadened forward-masked tuning curves from intense masking tones: Delay-time and probe-level manipulations
Authors: Nelson David A. , Freyman Richard L.
Published: October 2005

Forward-masked psychophysical tuning curves were obtained from normal-hearing listeners under two conditions: lengthened delay time between masker and probe, and increased probe level. Both conditions required higher-level masking tones and both conditions resulted in broader tuning curves. Comparisons were made of tuning curves obtained with different probe-level and delay-time combinations that were chosen to require equivalent masker levels at the probe frequency. Nearly identical tuning-curve shapes were obtained when masker level at the probe frequency was the same. The results are predicted by a two-process model, consisting of a nonlinear filter followed by an exponential decay. Tuning-curve shapes in forward masking appear to be largely dependent upon the masker level (filter output level) at which one attempts to measure them.
Initial observations concerning developmental characteristics of labio-mandibular kinematics
Authors: Smith Bruce L. , Gartenberg Terri E.
Published: October 2005

Acoustic measurements have shown that children’s speech segment durations are often longer than those of adults. It is unclear from previous research, however, why this occurs. One possibility is that children’s less mature peripheral speech mechanisms limit the rate at which they can perform articulatory movements and that this results in longer acoustic segment durations. Another possible cause of children’s longer segment durations is that ‘‘higher-order,’’ organizational factors might affect their ability to plan and sequence phonetic strings. This too could limit the rate at which they produce speech gestures, thus resulting in longer segment durations. The present study attempted to clarify such issues by obtaining articulatory movement data from four children and three adults using strain gage instrumentation to monitor superior–inferior lip and jaw displacement and velocity. Results indicate that the children tended to move their articulators more slowly than the adults, despite the fact that both groups exhibited comparable articulatory displacements. Differences observed between the adults and children concerning vocal tract size and movement variability indicate that ‘‘lower-level,’’ physical factors may be partially involved in children’s slower articulatory movements. However, differences between the two groups regarding anticipation of certain articulatory sequences suggest that ‘‘higher-order,’’ organizational effects may also be associated with children’s slower movements and, therefore, their longer segment durations.
Improved 1-Bark bandwidth auditory filter
Authors: Sekey Andrew , Hanson Brian A.
Published: October 2005

A critical band filtering function attributed to Schroeder [A. J. Fourcin et al., ‘‘Speech processing by man and machine,’’ in Recognition of Complex Acoustic Signals, edited by Theodore H. Bullock (Dahlem Konferenzen, Berlin, 1977)] is modified to (i) ensure 1-Bark bandwidth, (ii) have asymptotic slopes which reflect filtering characteristics of the human ear, and (iii) attain its maximum at 0 Bark. A bank of the new filters spaced at 1-Bark intervals is presented, and its smoothing effect on a vowel spectrum is illustrated.
Theoretical and experimental study of the contribution of radial modes to the pulsed ultrasonic field radiated by a thick piezoelectric disk
Authors: Baboux J. C. , Lakestani F. , Perdrix M.
Published: October 2005

A theoretical model is presented for evaluating the transient field radiated on the axis of a thick piezoelectric disk, by vibrations propagating radially on the circular transmitting face, from its rim towards its center. We had previously considered these vibrations to account for two unexpected signals (denoted S1 and S2), which were observed by measuring, with a miniature probe, the field produced in a liquid by a barium titanate disk (25 mm in diameter, 20 mm in thickness). These signals S1 and S2, not described by the well-known piston model, are due to vibrations which propagate radially on the disk face at two different speeds (5.0 × 103 and 2.6 × 103 m/s); we have called them radial vibrations as a simplification. Here, a simulation is undertaken to explain the complex changes observed in the amplitude and in the shape of signals S1 and S2, when the distance from the disk face varies. In this theoretical approach, it is assumed that the disturbance initially located on the rim of the disk face remains unchanged during its propagation along a disk radius. With these simplifying hypotheses, different analytical expressions for the impulse velocity potential φi (t) are obtained, each of them valid in a limited area of the disk axis. The resulting transient pressure p(t) is then used to predict the signals detected by the miniature probe. For this simulation we have taken account of the time dependence of the initial motion, together with the response of the measuring device. Several plots are chosen to illustrate the influence of different parameters such as the speed of the radial vibration or the duration of the input excitation signal. Finally, the comparison with the experimental results proves the efficiency of our model to describe the main characteristics of the signals produced by the radial vibrations: their contribution is important only close to the disk face and the position of a particular point on axis, called focus, is correctly predicted. Different possible improvements in the modeling are also discussed.
The forward and backward projection of acoustic fields from axisymmetric ultrasonic radiators using impulse response and Hankel transform techniques
Authors: Medeiros Anthony F. , Stepanishen Peter R.
Published: October 2005

A generalized impulse response formulation to evaluate the harmonic pressure field of ultrasonic planar vibrators having axisymmetric nonuniform surface velocity distributions is presented. The harmonic pressure is expressed as a Fourier transform of a generalized impulse response which is a function of the spatially nonuniform velocity of the vibrator. A backward projection method is then developed to reconstruct the normal surface velocity of axisymmetric vibrators from harmonic field pressures using an angular spectrum or Hankel transform formulation. The numerical accuracy of the backward projection technique is evaluated using the impulse response formulation to evaluate the pressure fields for several velocity distributions on disk vibrators. Experiments were performed to reconstruct the velocity distributions over the surface of a uniformly driven piezoelectric ceramic disk and ceramic ring using farfield measurements of the complex pressure. The experimental results were in good agreement with theoretical results based on the electrode patterns of the transducers.
The nonlinear free vibration of a damped elastic string
Authors: Gough Colin
Published: October 2005

A theoretical analysis of the large-amplitude free vibration of a damped elastic string shows that the perturbation in vibrational frequency and the precession of any orbital motion of the string about its equilibrium position resulting from nonlinearity is simply related to the mean-square radius and area of the orbital motion. A computer simulation of the coupled nonlinear equations of motion and measurements made on a loosely stretched string confirm our theoretical predictions, which differ from those of an earlier analysis by Anand [J. Acoust. Soc. Am. 45, 1089–1096 (1969)]. The significance of nonlinear string vibration is considered for musical instruments.
Extension of the image model to arbitrary polyhedra
Authors: Borish Jeffrey
Published: October 2005

In this paper, the image model is extended to arbitrary polyhedra with any number of sides. This generalization makes it possible to model real concert halls much more accurately. The image positions computed by the method can be reduced to the directional impulse response in order to create audible simulations of the concert hall. Also, the image model can provide insight into the fundamental acoustical properties of different concert hall geometries. For example, the extended image model demonstrates that rectangular halls have an advantage over fan-shaped halls with regard to spatial impression. We also show why the image model has fundamental advantages over another popular modeling technique, ray tracing.
Underlying dimensions and individual differences in auditory, visual, and auditory–visual vowel perception by hearing-impaired children
Authors: Busby P. A. , Tong Y. C. , Clark G. M.
Published: October 2005

Vowel perception studies were conducted on a group of four adolescent children with congenital profound sensorineural hearing impairments in the three conditions of audition alone, vision alone, and audition plus vision. Data were analyzed using the alscal multidimensional scaling procedure to identify the underlying dimensions and individual differences in dimension emphasis. The three dimensions obtained from the analysis of data for the audition alone condition were interpreted as the parameters of first and second formant frequencies, and vowel length. The one dimension for the vision alone condition was interpreted as the parameter of the width of the internal lip opening. The three dimensions for the audition plus vision condition were interpreted as the parameters of first formant frequency, vowel length, and the width of the internal lip opening. Subject variations in parameter preferences were observed for the audition alone and audition plus vision conditions but not for the vision alone condition.