bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency selectivity of the cochlea for formant peaks at high signal levels
Authors: Hall J. L.
Published: October 2005

The frequency selectivity for formant peaks in a synthetic continuous vowel was measured on a nonlinear model for motion of the basilar membrane. In spite of the fact that the model becomes more broadly tuned at high levels, the formant peaks in the model response become more sharply defined. This effect is caused by nonlinear suppression of the response to frequencies between adjacent formant peaks.
An analysis of a low-frequency model of the cochlea
Authors: Holmes Mark H.
Published: October 2005

An analysis is made of the low-frequency behavior of a three-dimensional hydroelastic model of the cochlea. In essence, the fluid motion is described using the linearized Navier–Stokes equations and the basilar membrane is modeled as an elastic plate. It is found that, for the lower frequencies, resonating frequencies are present and are approximately 4 Hz apart. The problem is solved and an analysis is made of the effects of the geometry on the motion of the wave. To conclude, an asymptotic formula is derived for the place of maximum amplitude and it is found to compare favorably with von Békésy’s experimental results.
Depression of the guinea pig cochlear temperature caused by anesthesia and ventral-approach ear surgery
Authors: Nuttall Alfred L. , La Rouere Michael J.
Published: October 2005

A chronic implant of a thermocouple, on the round window membrane of the guinea pig cochlea, was used to determine the cochlear temperature in awake, anesthetized, and surgically dissected animals. The normal cochlear temperature was equal to the core (rectal) temperature of the guinea pig (38.5 °C) and, in the intact animal, exactly tracks changes in core temperature at least down to the 33 °C level tested here. Ventral surgery to expose the cochlea results in a decrease, to a low value of 31 °C, in cochlear temperature because of the removal of tissue mass overlying the auditory bulla. Effective use of a heating pad and blanket cover, over the body of the guinea pig, will regulate core temperature but the exposed cochlea will always have a lower value than either the temperature measured rectally or in the orophraynx.
Horizontal contact resonances of vibration pickup with rectangular bases on soil surfaces
Authors: Omata Sadao , Morita Sakae
Published: October 2005

The horizontal contact resonance, which is formed by the resonant system due to the mass of a vibration pickup and the contact compliance of a setting point, causes errors in measurement and places restrictions on the measurement frequency range. The characteristics of the horizontal resonance depend on the type and condition of the ground surface and the method of planting the vibration pickup. This paper indicates the characteristics of the horizontal contact resonances of the rectangular vibration pickup with various base shapes, and derives expressions for a coupled motion of the pickup. It is suggested that the horizontal resonance and the response of the coupling system of the rectangular vibration pickup are significantly affected by the height of the center of gravity, the base area, and the base shape. The relationships are represented by a simple curve for the horizontal resonance. The agreements between the analog equations derived here and the values of the measurement on actual fields are well within the accuracy required for engineering analysis. The derived solutions provide adequate accuracy for practical applications to machine foundations with various rectangular bases.
Aural distortion product f
l+f
h: Growth rate and phase characteristics at different frequencies
Authors: Erdreich John
Published: October 2005

This paper addresses the question of whether the nonlinear amplitude response of the ear depends only on stimulus level or on both level and frequency. The level of the quadratic distortion product fh+fl was estimated using the tone-on-tone masking paradigm under a 2AFC transformed UP–DOWN procedure. The higher frequency tone (fh) was maintained at 1.2 times the lower (fl=250, 500, 1000, or 2000 Hz). Changes in the maximum and minimum threshold as maskee phase changes, [the monaural phase effect (MPE) amplitude], changes in the phase of the aural distortion product, and changes in the growth of the combination tone amplitude were examined as functions of primary frequency and level. The results indicate that MPE amplitude is simply a function of S/N ratio between the combination tone and the masking at that frequency. Distortion product phase varies over 360 ° with respect to the primary tones and is unrelated to primary frequency or intensity. Within listeners the range of distortion product phase is more narrow (70–90 deg) at a single frequency. The absolute level of the summation tone does not correlate well with primary frequency and the growth rate of the combination tone varies with frequency and observers over a range of 1.1–2.3 dB/dB. The results suggest frequency independent nonlinearity when the ratio of primary frequencies is constant.
Evidence for two temporal processes in forward masking
Authors: Penner M. J.
Published: October 2005

Evidence is provided from forward masking conditions of an auditory detection study demonstrating that an early temporal integration system summates auditory information for 3 msec or less. The output of this early system is the input to another system that applies a compressive nonlinear transformation and summates auditory information for a considerably longer period of time.
Multidimensional scaling of quality judgments of speech signals processed by hearing aids
Authors: Punch Jerry L. , Montgomery Allen A. , Schwartz Daniel M. , Walden Brian E. , Prosek Robert A. , Howard Mary T.
Published: October 2005

Perceptual dimensions underlying similarity ratings and preference judgments of the quality of hearing-aid-processed speech were derived via multidimensional-scaling procedures, and were correlated with 15 indices of electroacoustic performance to determine those electroacoustic characteristics contributing maximally to quality judgments. Connected discourse was tape recorded through 20 conventional hearing aids and presented in a paired-comparison paradigm to ten normal listeners for similarity ratings and quality preference judgments. Analysis of the group similarity matrices revealed only one definitive perceptual dimension, low-cutoff frequency, that was common to the listeners. In a three-dimensional INDSCAL solution, this electroacoustic factor correlated −0.87 with dimension 1. Listeners strongly preferred hearing aids with relatively low low-cutoff frequencies; dimension 1 correlated −0.76 with their preferences. The quality judgments of some listeners were found via KYST analysis to exhibit a multidimensional structure, with low-cutoff frequency remaining the most salient dimension. Secondary dimensions varied across these several listeners, and included response irregularity, equivalent input noise level, high-cutoff frequency, and intermodulation distortion. Thus, the data provided evidence that, while low-cutoff frequency dominates listener judgments, a multidimensional model may underlie the perceptual strategies used by some listeners to form quality judgments of hearing-aid-processed speech.
A real-time direction finding device for determining the bearing to the underwater sounds of Southern Right Whales, E
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Authors: Clark Christopher W.
Published: October 2005

The correlation of sounds with behavior in groups of free-ranging whales has been restricted by the difficulty of determining which animal made the sound. A real-time device was designed and built to directionalize on the underwater sounds of Southern Right Whales, Eubalaena australis. The device measures the phase difference between the signals from a two-dimensional hydrophone array and calculates a bearing to the sound source. Results of field calibration tests demonstrated that the system could reliably directionalize on right whale sounds with a resolution of ±12° except for arrival bearings within 25° of the array’s axis.
Beamforming when the sound velocity is not precisely known
Authors: Hinich Melvin J.
Published: October 2005

Beamforming is an integral part of most signal processing systems in active or passive sonars. The delays used to generate a beam are functions of the sound velocity, which depends on temperature, salinity, and pressure. There is a loss in array gain if the delays are incorrectly set. This will occur when the sound velocity in the water surrounding the hydrophones is different from the velocity that was used to set the delays. This paper makes two points: (1) fixed delay line sonars suffer a loss in gain when the true sound speed in the water is different from the velocity that is used to set the delays, and (2) there are signal processing techniques for two- or three-dimensional arrays that yield source bearings that are independent of the true sound velocity. These techniques require variable time delays, which can be realized using digital processing.
Computation of the Hankel transform using projections
Authors: Oppenheim Alan V. , Frisk George V. , Martinez David R.
Published: October 2005

In this paper two new algorithms for computing an nth-order Hankel transform are proposed. The algorithms are based on characterizing a circularly symmetric function and its two-dimensional Fourier transform by a radial section and interpreting the Hankel transform as the relationship between the radial section in the two domains. By utilizing the property that the projection of a two-dimensional function in one domain transforms to a radial section in the two-dimensional Fourier transform or inverse Fourier transform domain, several efficient procedures for computing the Hankel transform exploiting the one-dimensional FFT algorithm are suggested.
Predicting the post-detection data load for passive sonars
Authors: Short Robert D. , Toomey John P.
Published: October 2005

A technique for predicting the expected number of shipping-produced lines in an observed underwater acoustic ambient noise spectrum is described. The method is based on a mathematical model which includes the sonar equation, available information on the acoustic signatures of individual ships, and data concerning the oceanic distribution of shipping. The average number of detectable spectral lines in a given frequency band (line density) is shown to depend on the location of the sensor, sea state, and frequency. The line density also depends on the parameters of the sensor system. The results of calculations based on the model imply, for example, that the spectra observed with more directive receivers will contain more spectral lines. The results and methods described have application to passive sonar systems engineering.
Effect of reverberation and noise on the intelligibility of sentences in cases of presbyacusis
Authors: Duquesnoy A. J. , Plomp R.
Published: October 2005

For 80 male subjects (age 60–90) and 30 female subjects (age 71–89) the monaural Speech–Reception Threshold (SRT) for sentences was investigated under five reverberation conditions at a constant noise level. The reverberation times used were between 0 and 2.3 s. The noise, with the long-term average speech spectrum, had a level of 52.5 dBA. Each subject was assigned to one of several subgroups formed on the basis of the maximum reverberation time at which the subject was still able to understand the sentences correctly. The mean SRTs and the standard deviations are given, per subgroup, as a function of reverberation time. It is shown that, for each subgroup, the SRT in different reverberant sound fields can be expressed as a single number, namely the required Speech Transmission Index (STI) as introduced in room acoustics by Houtgast and Steeneken [Acustica 28, 66–73 (1973)]. Furthermore, it is shown that a model of SRT as a function of noise level, developed by Plomp [J. Acoust. Soc. Am. 63, 533–549 (1978)], can be combined with the STI model and can thus include the effect of reverberation.
Representative hearing levels by race and sex in North Carolina industry
Authors: Royster L. H. , Royster J. D. , Thomas W. G.
Published: October 2005

An extensive sample of North Carolina industrial audiometric test data has been compiled. The sample includes data from several different types of industrial environments, with the size of the industries represented ranging from less than fifty to over eight thousand employees. The total population considered is in excess of 14 000 employees. The data are examined using analytical techniques developed over the past six years while investigating the effectiveness of industrial hearing conservation programs. One of the findings is significant differences in the initial hearing threshold levels by race and sex. A second observation is differences by race and sex in the change in hearing levels with time. It is concluded that the hearing levels of industrial employees differ significantly by race and sex. The differences are of such magnitude that meaningful evaluations of industrial audiometric data bases are not possible unless the race and sex compositions of the population are considered.
Transfer function method of measuring in-duct acoustic properties. II. Experiment
Authors: Chung J. Y. , Blaser D. A.
Published: October 2005

This paper is the second of two papers describing the transfer function method of measuring in-duct acoustic properties. In the previous paper the theoretical formulae were developed. In this paper experimental results are presented to demonstrate the accuracy and the general utility of the method. Test results of the complex reflection coefficient, the complex acoustic impedance, and the transmission loss are found to agree well with theoretical predictions. The sound absorption coefficient was evaluated with both the new method and the conventional Standing-Wave-Ratio (SWR) method and the accuracy of the two results are found to be comparable. The new method, however, is about 40 times faster than the SWR method. Also included are experimental verifications of two methods for improving the transfer function estimate, namely the use of sensor switching for automatic system calibration and the use of coherence functions for signal enhancement.
Steady-state response of internally damped circular plates
Authors: Irie Toshihiro , Yamada Gen , Takeda Yuri
Published: October 2005

The steady-state nonaxisymmetrical response of a circular plate and an annular plate with internal damping to a sinusoidally varying force is determined by the modal analysis. The transverse deflection of the plates is expressed by use of the Green function of the plates, and the driving-point impedance and transfer impedance are obtained analytically. The method is applied to a simply supported circular plate and a free-clamped annular plate driven at an arbitrary point; these responses of the plates are calculated numerically, and the effects of the internal damping and the location of the driving point on them are discussed.
The contribution of normal modes in the bottom to the acoustic field in the ocean
Authors: Macpherson Mark K. , Frisk George V.
Published: October 2005

The effects of normal modes in the bottom on the acoustic field in the ocean are examined. The ocean bottom model consists of a slow isovelocity layer overlying an isovelocity half-space to simulate the characteristic sound velocity drop at the water–bottom interface. Attention is focused on the perfectly trapped modes which are excited in the layer by inhomogeneous waves emitted by a point source in the water column. The relative normal mode contribution to the total acoustic field in the water is calculated analytically for a near-bottom source/receiver geometry and evaluated for representative ocean bottom examples. It is shown that, for combined source/receiver heights less than a wavelength, the field is dominated by the leaky mode contribution at short ranges (≲2 km) and the trapped mode contribution at long ranges (≳2 km). For fixed bottom parameters, the trapped mode contribution increases exponentially with decreasing combined source/receiver height. It is also shown that, for a fixed layer wavenumber–thickness product and fixed layer sound speed, the leaky mode fields at different frequencies are approximately range-scaled versions of the same field.
Low-frequency cw coherence measurements for long underwater paths
Authors: Robertson G. H. , Wagner R. L.
Published: October 2005

Measurements were made to determine the first-order effects limiting the coherence of continuous-wave signals received on underwater hydrophones. It was found that phase fluctuations among the various hydrophones are the most serious deviations from ideal reception. These fluctuations were found to have a relatively unimportant short-term component and a dominant long-term component with a typical period of about 30 min. The fluctuations increased in magnitude as the spacing of the hydrophones was increased. The coherence computed from the phase data was about 0.5 at 22 ft and 0.15 at 2000 ft. These measurements were made primarily with a 270-Hz bottomed source at Eleuthera and receiving hydrophones on the bottom at Bermuda, approximately 700 nautical miles away.
Ears adapted for the detection of motion, or how echolocating bats have exploited the capacities of the mammalian auditory system
Authors: Neuweiler G. , Bruns V. , Schuller G.
Published: October 2005

Bats use the rich food resources of the night by specializing in audition. They emit short echolocation sounds and listen to the echoes returning from potential prey. The bat’s auditory system analyzes spectral and temporal parameters of echoes for detecting, locating, and identifying a target. Different bat species have solved the problem of acoustic target detection and pattern recognition even in clustered situations by focusing on certain acoustical features of a target. The specialized motion detection by horseshoe bats, for instance, analyzes small echofrequency shifts modulated onto a long constant frequency echolocation signal. These frequency modulations are Doppler shifts within echoes returning from wing beating insects. For detecting modulations as small as 10 Hz or 0.01%, horseshoe bats have in the cochlea an extremely narrow filter (Q?500) matched to the carrier frequency (i.e., echolocation sound) of 83 kHz. The filter is realized by structural differentiations of the basilar membrane and the filter frequencies are represented on the basilar membrane in an expanded fashion. We have called this specialized patch of the basilar membrane an ’’acoustical fovea.’’ The ’’foveal frequencies’’ are largely overrepresented in the tonopical arrangement of the ascending auditory pathway. The bats have developed a feedback system which lowers the emitted frequency during flight in such a way that the Doppler shifted echofrequency is kept precisely at a fixed reference frequency of the fovea. This feedback system and other neuronal data disclose an intricate coupling of the auditory and vocalizing system. The evolution of echolocation in bats has driven the analyzing capacities of audition in both frequency and time domain close to theoretical limits. Investigations of such specialized systems give fascinating insights into capacities and possible general principles of auditory information processing.
Simple model for low-frequency guitar function
Authors: Christensen Ove , Vistisen Bo B.
Published: October 2005

The frequency response of sound pressure and top plate mobility is studied around the two first resonances of the guitar. These resonances are shown to result from a coupling between the fundamental top plate mode and the Helmholtz resonance of the cavity. A simple model is proposed for low- frequency guitar function. The model predicts frequency responce of sound pressure and top plate mobility which are in close quantitative agreement with experimental responses. The absolute sound pressure level and mobility level are predicted to within a few decibels, and the equivalent piston area of the top plate is determined. All parameters of this model can directly be derived from measurements of the frequencies of the two first resonances and of the cavity Helmholtz resonance. The Helmholtz resonance is found as the antiresonance in the spectrum of top plate mobility.
Gap detection by the chinchilla
Authors: Giraudi Diane , Salvi Richard , Henderson Donald , Hamernik Roger
Published: October 2005

Five monaural chinchillas were trained with a method of shock-avoidance conditioning to respond to silent intervals, or gaps, in an otherwise continuous noise. The noise was low-pass filtered at either 10 or 6 kHz and presented at six intensities ranging between 23- and 77- dB sound-pressure level (SPL). Gap detection thresholds were determined according to the method of constant stimuli. For both noise bands, gap thresholds were approximately 3 ms at the highest intensity levels and increased to approximately 6 ms at the lowest level. The results obtained from the chinchilla are in general agreement with those obtained from man.
Mechanism and frequency distribution of two-tone suppression in forward masking
Authors: Moore Brian C. J.
Published: October 2005

These experiments are concerned with the frequency distribution of two-tone suppression in forward masking. In each experiment the threshold of a 20-msec probe tone following a 300-msec masker was determined as a function of probe frequency. In experiments I and II this was done for two maskers (a single tone with frequency fm, and that tone with a suppressing tone added) which had previously been equated for their masking effectiveness at fm by adjusting the levels of the components at fm. The maskers were equally effective only in a restricted frequency region around fm, a result which is not consistent with the idea that suppression is equivalent to a simple reduction in level of the suppressed tone. In experiment III probe thresholds were measured for a fixed tone at 2 kHz with and without a suppressing tone whose frequency was systematically varied. The suppression, measured as the reduction in probe threshold produced by adding the suppressing tone, was found to have two components. One of these was limited to a narrow range of probe frequencies around 2 kHz and is attributed to a qualitative change in the cues available to the observer when a suppressing tone is added to the masker. The other component shifted in frequency as the suppressor frequency was altered and is explained as a reduction in level of only part of the excitation pattern of the suppressed tone.
Psychophysical measurements relating suppression and combination tones
Authors: Shannon Robert V. , Houtgast T.
Published: October 2005

Measurement of the combination tone 2f1-f2 with the pulsation-threshold technique yields a significantly lower value than measurement with the cancellation procedure. For three or four subjects, the difference between these two measures equals the amount of suppression produced at 2f1-f2 by the lower primary, f1. It appears that the cancellation procedure overestimates the combination-tone by f1. For a fixed level of f1, the level of the combination tone first increases, then decreases as the level of f2 is raised, for both cancellation and pulsation measures. The level of f2 at which these functions reach a peak is the same level at which f2 begins to suppress the lower primary, f1.
Effects of nonlinearities on speech encoding in the auditory nerve
Authors: Sachs Murray B. , Young Eric D.
Published: October 2005

The representation of steady-state vowels in terms of both average rate and temporal aspects of the discharge patterns of populations of auditory-nerve fibers is discussed. The effects of auditory-nerve nonlinearities on this representation is emphasized. Aspects of two rate-related nonlinearities, rate saturation and two-tone suppression, are reviewed. At low sound levels, profiles of discharge rate versus characteristic frequency in populations of auditory-nerve fibers show well-defined peaks at frequencies corresponding to the formants of a vowel stimulus. At levels above about 60 dB SPL, these peaks are not seen because of a combination of rate saturation and two-tone suppression. Units with spontaneous rates less than 1/s show the effects of suppression more dramatically than do units with higher spontaneous rates; nonetheless, this population can retain formant peaks in its rate profiles up to levels at least 20 dB higher than does the higher spontaneous rate population. Aspects of phase-locking to tones and two-tone combinations, including synchrony suppression, are reviewed. Temporal patterns of responses to vowels are analyzed in terms of interval histograms. This analysis shows that in general, phase-locking to the formant frequencies is stronger than locking to other harmonics of the stimulus. As sound level increases, synchrony to the formant frequencies saturates. However, responses to nonformant harmonics are suppressed by responses to the formant harmonics. This synchrony suppression allows the phase-locking to the formant frequencies to remain dominant even at high levels. The exception to this behavior is locking to harmonics and intermodulation products of the first two formant frequencies (2F1, 3F1, F2-F1, etc.) which increases rapidly in amplitude at higher sound levels. These distortion products are, to some extent, a consequence of the rectification inherent in hair cell/nerve fiber transduction and may also reflect the presence of propagating combination tones.
Electroacoustic sensitivity of composite piezoelectric polymer cylinders
Authors: Ricketts Donald
Published: October 2005

The low-frequency electroacoustic sensitivity of piezoelectric polyvinylidene fluoride (PVF2) film attached to a cylindrical tube substrate is derived for three boundary conditions. Sensitivity expressions are developed for both the PVF2 film attached to the inside or outside surface of the tube for each of the three boundary conditions. Experimental verification of the theory has been obtained for the capped composite polymer cylinder, with close agreement between the theoretical and measured sensitivities.
Basic problems caused by depth and size constraints in low-frequency underwater transducers
Authors: Woollett Ralph S.
Published: October 2005

Scaling of a conventional transducer design to very low frequencies usually leads to greater power than needed and greater size than is considered tolerable. Normally, therefore, scaling guidelines are abandoned, and very low frequency transducers are miniaturized, that is, made with dimensions much smaller than the sound wavelength. The resulting low radiation resistance leads to high mechanical Q, poor power-to-weight ratio, and poorly behaved driving-point impedance. By employing electrical equalizers and acoustoelectrical feedback, the designer can achieve broad bandwidth in spite of the high Q, but an oversized driving amplifier is required. Transducers that operate at full ocean depths are usually liquid-filled. The stiffness of the interior liquid increases the transducer size and tends to raise its Q and lower its coupling factor. A Helmholtz resonator configuration is often advantageous in this situation. For more moderate depths, compliant tubes or compressed gas may be used to reduce the stiffness of the interior. However, depth capability is always obtained at the expense of acoustic performance.
A technique for measuring the sound velocity difference in two liquids
Authors: Toda Kohji , Shinoda Yoshiaki
Published: October 2005

A new technique for measuring the sound velocity difference in two liquids is presented by using interdigital transducers in contact with the liquids. The phase difference between two delayed signals obtained at the output transducers, corresponding to the sound velocity difference, is converted to a dc voltage via a circuit with a function of phase comparation. As an example, the difference between the sound velocity in solutions of NaCl and that in water is given as a function of concentration. Basic design considerations for the device and experimental performance are given.
Correlation between estuarine sea floor acoustic reflection signatures and engineering sediment measurements
Authors: LeBlanc Lester R. , Middleton Foster H. , Nacci Vito A. , Cohn Ralph F.
Published: October 2005

A recently developed technique is investigated for the analysis of sea floor acoustic reflection data. The technique uses Empirical Orthonormal Functions (EOF’s) to analyze the entire acoustic echo from the sea floor. In previous work [Milligan et al., J. Acoust. Soc. Am. 64, 795–807(1978)], the technique was used to ’’cluster’’ areas of similar acoustic behavior. This paper explores the relationship between the acoustic behavior of a sea floor sediment and classical engineering measurements. To achieve the objective, an experiment was configured so as to obtain acoustic reflection data and sediment measurements at the same spot on the sea floor. The results of this analysis showed that significant correlation exists between the acoustic waveform and certain measured sediment properties, and that an acoustic sediment classification scheme can be implemented.
Generalized shading formula from a given line shading
Authors: Lockhart Clayton M. , Miller Max K.
Published: October 2005

Beam patterns of arrays of sensors can now be optimized (low sidelobe level with minimum mainlobe width) by shading the array with amplitude weights that vary with incoming plane-wave angles. For the simple case of a one-dimensional array [x,f(x)], we demonstrate a method of shading for wide steering angles and give computer-simulated results. This method of shading is immediately applicable to two-dimensional arrays of the form [x,y,f(x)], and permits analysis of a restricted class of conformal arrays.
Superresolution ultrasonic imaging system using focused beam illumination and algebraic reconstruction
Authors: Sato Takuso , Sasaki Kimio , Horiuchi Masato
Published: October 2005

A superresolution ultrasonic imaging system is proposed that uses focused beam illumination of a region of interest and matrix correspondence of the detected hologram signal to its modeled wave field. The method described povides an image of the interior of the minimum point discernible with conventional focused beam imaging methods, that is, a superresolution image. The principle, construction, experimental results, and discussions of the superresolution systems are given. The results indicate approximately five times greater resolution than that available with conventional methods.
Numerical solutions of the parabolic wave equation: An ordinary-differential-equation approach
Authors: Lee Ding , Papadakis John S.
Published: October 2005

General purpose, efficient numerical ordinary-differential-equation (ODE) methods, combined with the employment of a predictor–corrector procedure, are introduced for solving the underwater acoustic parabolic wave equation. The formulation and theory of applicable ODE methods and a PCm procedure are outlined. Some results of ODE solutions for sound propagation from shallow to deep water with a sloping rigid bottom are included. The merits of ODE methods are discussed.
Cycle distances and attenuation in shallow water
Authors: Tindle C. T. , Weston D. E. , Payne S. G.
Published: October 2005

Recent results showing the equivalence of mode attenuation per cycle and reflection loss of the equivalent ray did not hold in shallow water with a small number of modes. The failure is demonstrated to be linked to the concept and definition of a mode cycle distance for low mode density. Attenuation rates of modes and average attenuation rates of rays are now shown to be equal for all mode densities, provided the attenuation is not too large and the ray cycle distance is taken as the sum of the geometrically traced ray distance and the boundary beam displacement.
Nonlinear oscillations of bubbles in compressible hydraulic oils
Authors: Fujiwara Tokuichi , Shima Akira
Published: October 2005

The nonlinear oscillation of a bubble in compressible hydraulic oils subject to periodic pulsating pressure was theoretically analyzed. According to the numerical calculations, the effect of compressibility of liquid on the oscillation of a bubble were clarified. That is, (1) the effect of compressibility is appreciable where the amplitude is large; (2) when compressibility is considered, the pressure threshold increases; (3) in the subharmonic of order 1/2, the effect of compressibility on the pressure threshold is almost constant over a wide range of initial bubble radius R0; (4) the effect of compressibility on the relation between ω/ω0 (a ratio of the circular frequencies of pulsating pressure and a bubble) and pressure threshold of the subharmonics 1/2 and 1/3 is almost constant covering the wide range of ω/ω0.
Analytical expressions for critical-band rate and critical bandwidth as a function of frequency
Authors: Zwicker E. , Terhardt E.
Published: October 2005

The critical-band rate as well as the critical bandwidth are functions of frequency. These dependencies have been given in table form. For effective use of these values in computers, relatively simple equations are given to express the dependence of critical-band rate on frequency with an accuracy better than 0.2 Bark and that of critical bandwidth on frequency with an accuracy better than 10% over the whole auditory range.
Speed of sound in air as a function of frequency and humidity
Authors: Morfey C. L. , Howell G. P.
Published: October 2005

The model of atmospheric air given in ANSI S1.26–1978 (’’Method for the Calculation of the Absorption of Sound by the Atmosphere’’) has been used to predict the frequency and humidity dependence of the sound speed in air. Good agreement with existing measurements is demonstrated, apart from an unexplained discrepancy at low relative humidity.
The hydrophone–pinger experiment
Authors: Bryan George M.
Published: October 2005

The compressional-wave velocity in the uppermost sediments near the sea floor has been measured with high resolution, in deep water, by a variable-offset technique in which source and receiver are at the sea floor. The receiver is a single hydrophone connected through a 300-m length of seismic cable to an STD wire leading to a shipboard winch. The source is a 3.5-kHz pinger clamped to the STD wire and transmitting 1-ms pulses at 1-s intervals. With the phone on the sea floor together with the piled-up cable, the pinger drifts with the ship, moving away from the hydrophone until the cable comes taut, thus ending the run. Maximum offset is of the order of a few hundred meters (the length of the cable) and velocity structure can be obtained to depths of 100 or 200 m into the sediment. Interval velocities in layers as thin as 7 m in water depths in excess of 5000 m have been resolved by the method.
Harmony and nonharmonic partials
Authors: Mathews Max V. , Pierce John R.
Published: October 2005

We have explored some musical effects of tones with nonharmonic partials. The spacing of partials can be stretched so that each partial frequency fij present in tones sounded singly or together is given by fij=Ai/12+log2j. Here i is the scale step in semitones, j is the partial number, and A is the frequency ratio of a pseudo-octave (A=2 for a true octave). We find that subjects can match the keys of stretched (A=2.4) as well as unstretched passages. Stretched cadences (A=2.4) do not seem final. But, a stretched ’’cadence’’ with equally spaced partials that goes from closely spaced (tonally dissonant) to widely spaced (tonally consonant) partials does seem final. Our experiments do not decide finally among three views of harmony: that harmony depends on a fundamental bass or periodicity pitch (Rameau), that harmony depends on the spacing of partials (Helmholtz and Plomp) or that harmony is a matter of brainwashing.
A simplified, robust training procedure for speaker trained, isolated word recognition systems
Authors: Rabiner L. R. , Wilpon J. G.
Published: October 2005

One of the most important operations in isolated word speech recognition systems is the method used to obtain the word reference templates. For speaker trained systems, the techniques that have been used include casual training, averaging, and use of statistical pattern recognition clustering methods. In a recent study, Rabiner and Wilpon showed that the statistical techniques, when combined with the technique of averaging the autocorrelation coefficients of all tokens within the cluster, provided a reliable, robust set of reference templates. The only drawback to this method was the extensive, burdensome training required for the statistical analysis. Since the statistical training method could not be used in most practical situations, techniques were investigated for obtaining a simplified, robust training procedure which would incorporate many of the ideas of the statistical approach. Such a training method is described in this paper. The advantages of this new training procedure, over (previously used) casual training include: ease of use, robustness of the templates, minimized computation in the recognition algorithm, normalized durations of all references, and recognition accuracy comparable to previous systems with double the number of templates.
Discomfort produced by impulsive whole-body vibration
Authors: Griffin Michael J. , Whitham Eleri M.
Published: October 2005

This paper reports four whole-body vibration experiments conducted to determine the effects of ’’pulse’’ duration and combinations of ’’pulses’’ of vibration on human discomfort. The first experiment investigated the variation in discomfort with vibration duration for the frequencies 4, 8, 16, and 32 Hz and durations from one cycle of motion to 4 s. The second experiment extended the results for 8-Hz vibration to durations up to 32 s. The third experiment involved complex motions with one predominant frequency and root mean square acceleration level but differing peak levels. The final experiment investigated the effect of vibration duration at different vibration frequencies. The results of the first two experiments conflict with previous reports of a short finite integration time for human response to vibration. The data are used to devise a procedure for predicting the discomfort of the motions used in the third experiment. The procedure which is based on a ’’root-mean-quad’’ unit: rmq=[T−1ℱT0a4(t) dt]1/4 indicates that motions of the same frequency and same rms level will cause greater discomfort with increasing peak levels. The predictions are in good general agreement with the experimental results. Possible uses of the rmq unit are discussed.
Sound propagation in a temporally varying waveguide
Authors: Ahluwalia Daljit S. , Reiss Edward L. , Stickler David C.
Published: October 2005

The effects of temporal variations of the sound velocity on acoustic propagation from a time periodic point source in a layer of uniform depth h are studied. It is assumed that the sound speed is a slowly varying function of time, and that the upper and lower surfaces of the layer are free and rigid, respectively. An asymptotic expansion of the acoustic pressure field is obtained by using the methods of normal modes, two times and stationary phase evaluations of multiple integrals. The small parameter ε that is used in the analysis is the ratio of the time scale of variation of the sound velocity to the frequency of the source. To lowest order in ε, the acoustic pressure is given by the sum of a primary wave and a secondary wave. The primary wave consists of a finite modal sum of propagating waves and an infinite modal sum of evanescent waves. If the dimensionless sound speed oscillates about the value 1/am, where am is the propagation number of the mth mode, then the mth mode alternates between propagating, and evanescent, i.e., the mth mode will alternately propagate and ’’fade.’’ In addition, it is shown that in the farfield the secondary wave is an infinite sum of evanescent waves which decay more rapidly than the evanescent components of the primary wave. Finally, it is shown that the long time, farfield limit of the primary wave is equivalent to the customary ’’approximation’’ that is obtained by first seeking time periodic solutions, where the initial conditions and the variations in the sound velocity are neglected. Then, the time dependence of the sound velocity is inserted into the resulting representation.
R-matrix theory of sound scattering from fluid spheres via the Mittag–Leffler expansion
Authors: Gaunaurd G. , Überall H.
Published: October 2005

The R-matrix formalism of nuclear reaction theory is applied to the classical problem of wave scattering by an obstacle, as exemplified by acoustic scattering from fluid spheres imbedded in another fluid. The modal mechanical impedance of the system is a meromorphic function of the Wigner R type, which may be represented by a Mittag–Leffler series exhibiting its poles. The scattering function Sn (a diagonal S matrix) is represented in an exact fashion by R, and in the one-level approximation it reduces to the analytic function we obtained in our previous studies, with resonance-level shifts and widths introduced by the R-matrix formalism. Absorption in the obstacle or in the medium causes further shifts and broadening of the widths. Graphs of the R function and of the modal resonances as found from various level approximations are displayed and discussed.
Sound radiation from a finite length unflanged circular duct with uniform axial flow. II. Computed radiation characteristics
Authors: Johnston G. W. , Ogimoto K.
Published: October 2005

Computed numerical results are presented for the sound radiation from a finite length unflanged hard wall circular duct with uniform axial flow both inside and outside the duct. The development of the necessary theory is outlined in part I of this report. In the present report, some of the finite duct effects are quantitatively presented for the simplest plane-wave excitation case, It is shown that the finite duct radiation problem exhibits two important physical phenomena. Firstly, length resonance effects lead to the creation of standing waves on either side of the source plane, in the duct interior. Secondly, the diffracted sound waves propagating from each duct end, interfere in the farfield producing a modified radiation directivity (relative to the semi-infinite duct radiation).
Cochlear micromechanics—A physical model of transduction
Authors: Allen J. B.
Published: October 2005

One of the basic questions which has persisted in the field of hearing theory is the still unresolved mechanical action of hair-cell transduction. The fundamental problem that has historically plagued researches is the discrepancy between mechanically measured tuning of basilar membrane motion and neurally measured tuning. In this paper we show that the difference between these two measures appears to be accounted for by a specific, physically motivated, micromechanical model. This model gives rise to a spectral zero which we identify as the ’’second-filter’’ of cochlear transduction. For high-frequency fibers this zero resides at a fixed frequency ratio below CF (characteristic frequency) while for fibers having low-frequency CF’s the zero appears to go to zero frequency faster than CF. In this paper we first present and analyze the assumed mechanical model. We then briefly discuss a possible specific physical realization for the nonlinearity of cochlea mechanics. The nonlinear model is based on dynamical variations in outer hair cell stereocilia stiffness.
Sound pressures in the basal turn of the cat cochlea
Authors: Nedzelnitsky V.
Published: October 2005

Techniques were developed for measuring sound pressure in the cochlea with calibrated, liquid-filled, piezoelectric probe microphones. Sound pressures were measured in scala vestibuli and scala tympani in the basal turn in 25 cats for tones from 20–10 000 Hz. Control experiments indicated that intracochlear pressures were essentially uninfluenced by the measuring technique, and were conducted to the cochlea via the ossicular chain. Intracochlear pressures are linearly related to pressure at the tympanic membrane for tone levels at least as high as 105 dB SPL, and are relatively independent of depth of probe insertion in the scalae. The transfer ratio of sound pressure in scala vestibuli to that at the tympanic membrane increases in magnitude over the frequency range 50–1000 Hz to reach a maximum value of 15–30 dB, and decreases at higher frequencies, thus demonstrating that the middle ear provides a frequency-dependent pressure gain. At frequencies below 40 Hz, the pressures in scala vestibuli and scala tympani are approximately equal and are both determined by the round-window membrane compliance. At frequencies above 100 Hz, the round-window membrane impedance is small compared to the acoustic input impedance of the cochlea, and the pressure in scala vestibuli considerably exceeds that in scala tympani; consequently, the pressure difference across the cochlear partition is approximately equal to the pressure in scala vestibuli.
Binaural detection of sonar signals
Authors: Kerivan John E.
Published: October 2005

Standard methods of presentation of sonar signals to operators have not maximized the capabilities of the auditory system. This report describes a dichotic method of sonar signal presentation to operators based on the masking-level-difference (MLD) principle in hearing. Using a Bekesy tracking procedure, twenty-six listeners of varied experience detected recorded broadband sonar targets and low-frequency pure tones that were embedded in 100 Hz–4 kHz recorded and synthesized backgrounds. The signals were either homophasic or antiphasic and the backgrounds were always homophasic. Average detection thresholds for the antiphasic sonar signals were 5–7 dB better than their homophasic counterparts. Pure tone antiphasic detection thresholds were also 6–11 dB better than in the homophasic presentation. The sonar signals show similar MLD’s as those found with speech signals.
Sidelobe suppression versus phase error characteristics of multistage modulation scanning sonar systems
Authors: Lynch J. F. , Pitt S. P. , Pruitt J. G.
Published: October 2005

The sidelobe level sensitivity of multistage modulation scanning sonar systems to internal electronic phase errors is examined by means of a ’’scanning function’’ approach and also by a hardware oriented analysis of a particular sonar system. It is shown that the later internal stages of such modulation scanning systems are the most sensitive to phase error. A general approach to calculating scanning sidelobe levels with phase error present is discussed.
The audibility of Doppler distortion in loudspeakers
Authors: Villchur Edgar , Allison Roy. F.
Published: October 2005

The existence of Doppler distortion in loudspeakers was demonstrated more than 30 years ago, but the question of whether or not such distortion is of significance in music reproduction has not been settled. In this study the audibility of Doppler distortion in simple direct radiators is investigated both theoretically and experimentally through (1) an analogy to tape-machine flutter, (2) an analysis of the effect of normal listening-room conditions on Doppler distortion (for a given low-frequency power the radiation-load and reverberant-field correction factors typically reduce this distortion to 0.36 of its value on the axis of a speaker radiating into anechoic half-space), and (3) double-blind listening tests. An eight-member jury compared music reproduced in two modes, one of which was essentially free of Doppler distortion. In one experiment, two recordings were made of the output of a speaker, one with a sharp bass-attenuation filter in the speaker input circuit and the other with the same filter moved to the microphone circuit. In a second experiment, on-axis and off-axis speaker output were recorded in an anechoic chamber, the speaker input circuits being compensated to make the frequency responses in the two modes equal. The theoretical analysis indicates that for any practical cone velocity Doppler distortion will be less audible by an order of magnitude than the flutter of a 15-ips tape machine that meets the NAB Standard. The experimental results provided confirming evidence that it is inaudible.