Showing papers in "Journal of the Acoustical Society of America in 1975"
TL;DR: In this article, it was shown that the problem of locating complex poles can be reduced to solving a polynomial with real roots whose order is one half that of the original all-pole transfer function.
Abstract: It has been known that the linear predictor coefficients (LPC) of speech signals can be transformed into a “pseudo” vocal‐tract area function whose boundary conditions are (a) a complete opening at the lips and (b) a matching resistance termination at the glottis. If the boundary condition at the glottis is replaced by a complete opening or a complete closure, all the poles of the resulting system function will move onto the unit circle in z plane. Using this fact it is possible to describe the original LPCs by two sets of pole frequencies corresponding to the two new boundary conditions at the glottis, or a set of frequency‐residue pairs corresponding to either set of poles. These representations have several important features: (1) If an original pole is narrow band, the new pole is close to the original pole; (2) the two sets of pole frequencies alternate and are ordered on the frequency axis; and (3) the problem of locating complex poles can be reduced to solving a polynomial with real roots whose order is one‐half that of the original all‐pole transfer function.
630 citations
TL;DR: A manikin for hearing aid and related acoustic research was designed with median human adult dimensions and found to be like a median human in acoustic response to free fields.
Abstract: A manikin for hearing aid and related acoustic research was designed with median human adult dimensions. Ear simulation matches the acoustic response with an auricle, an ear canal, and an eardrum that equal the median ear in dimensions, acoustic impedance and modes. Dimensions of torso and head are based on published anthropometric data, but the auricle is based on data obtained for this development. The ear canal and eardrum are adapted from the earlike coupler by Zwislocki. The ear entrance sound pressure was found to be relatively insensitive to surface or skin impedance of the head. Validating measurements show the manikin, designated KEMAR, to be like a median human in acoustic response to free fields.Subject Classification: 65.22, 65.80, 65.35,65.82.
423 citations
TL;DR: Oberved et al. as mentioned in this paper measured the relative velocity of air bubbles undergoing a mutual Bjerknes force in a rigid glass container oscillated in a vertical direction at 60 Hz by a shaker table.
Abstract: This paper concerns the translational forces exerted on pulsating air bubbles in a stationary sound field. These forces, normally called Bjerknes forces, are derived by simple arguments and classified as to their origin. Measurements have been made of the relative velocity of appoach of two bubbles undergoing a mutual Bjerknes force. The measurements were made in a rigid glass container oscillated in a vertical direction at 60 Hz by a shaker table. The ambient pressure above the liquid was reduced in order to obtain large pulsations, and the attracting bubbles were photographed with a movie camera. Oberved and calculated values for the velocity of approach are in agreement provided a drag law assuming interfacial slippage is used.Subject Classification: 25.60.
407 citations
TL;DR: It is suggested that inclusion of alternative fluent‐form syllabifications for multisyllabic words and the use of phonological rules for predicting syllabic contractions can further improve agreement between predicted and experimental syllable counts.
Abstract: As a first step toward automatic phonetic analysis of speech, one desires to segment the signal into syllable‐sized units Experiments were conducted in automatic segmentation techniques for continuous, reading‐rate speech to derive such units A new segmentation algorithm is described that allows assessment of the significance of a loudness minimum to be a potential syllabic boundary from the difference between the convex hull of the loudness function and the loudness function itself Tested on roughly 400 syllables of continuous text, the algorithm results in 69% syllables missed and 26% extra syllables relative to a nominal, slow‐speech syllable count It is suggested that inclusion of alternative fluent‐form syllabifications for multisyllabic words and the use of phonological rules for predicting syllabic contractions can further improve agreement between predicted and experimental syllable countsSubject Classification: 7040, 7060
296 citations
TL;DR: In this article, the authors derived expressions for speed and attenuation of compressional waves travelling normal to the boundaries of a laminated medium which consists of alternating layers of two fluid-saturated porous solids.
Abstract: Expressions are derived for speed and attenuation of compressional waves travelling normal to the boundaries of a laminated medium which consists of alternating layers of two fluid‐saturated porous solids. Fluid flow across boundaries is taken into account through approximate expressions, applicable at low frequencies, derived through extension of the approach used by Gassmann. Calculations show that when one of the saturating fluids is gas, substantial dispersion and extreme attenuation may result.
265 citations
TL;DR: In this paper, a comparative performance study of five pitch detection algorithms was conducted using a speech data base, consisting of eight utterances spoken by three males, three females, and one child.
Abstract: A comparative performance study of five pitch detection algorithms was conducted. A speech data base, consisting of eight utterances spoken by three males, three females, and one child was constructed. Both telephone and wideband recordings were made of each of the utterances. For each of the utterances in the data base a “standard” pitch contour was semiautomatically measured using a highly sophistocated interactive pitch detection program. The “standard” pitch contour was then compared with the pitch contour that was obtained from each of the five programmed pitch detectors. The algorithms used in this study were (1) a center clipping, infinite‐peak clipping, modified autocorrelation method; (2) the cepstral method; (3) the SIFT method; (4) the parallel processing time domain method; and (5) the data reduction method. A set of measurements were made on the pitch contours to quantify the various types of errors which occur in each of the above methods. Included among the error measurements were the average and standard deviation of the error in pitch period during voiced regions, the number of gross errors in the pitch period, and the average and standard deviation of the error in choosing onset and offset of voicing. By pooling the various error measurements, the individual pitch detectors could be rank ordered as a measure of this relative performance.
259 citations
TL;DR: This is a summary report of the vowel duration data that have been accumulated over the past several years, and the duration rules derived from the data are intended for use in the speech synthesis‐by‐rule system from printed text.
Abstract: This is a summary report of the vowel duration data that have been accumulated over the past several years. The data corpus analyzed to derive temporal controls of vowels consists mainly of three different readings by three different speakers, each about 10 to 20 min in duration. The rules cover the temporal behavior of vowels under many phonological conditions. The conditions include stressed and unstressed positions, prepausal and nonprepausal positions, word‐final and non‐word‐final conditions, and monosyllabic and polysyllabic words. The influence of following consonants is discussed as well. Included also are conditions other than phonological ones, such as the effect of the prominence of words on their vowels, and the speed of reading. The duration rules derived from the data are intended for use in our speech synthesis‐by‐rule system from printed text.Subject Classification: 70.20, 70.70.
259 citations
TL;DR: The results confirm the general features of previous measurements but demonstrate that the mechanical tuning properties of the basilar membrane are equally poor at low SPLs and under excellent physiological condition of the cochlea, as indicated by the threshold of the gross cochlear action potential to clicks.
Abstract: Measurements of amplitude and phase were made on the basilar membrane and middle ear of guinea pigs. A subminiature capacitive probe giving wide dynamic range and linearity was used in conjunction with a slave filter to provide continuous frequency response records and a lock−in amplifier to provide high−sensitivity measurements on the basilar membrane down to 40 dB SPL. The results confirm the general features of previous measurements using various optical and Mossbauer techniques but also demonstrate that the mechanical tuning properties of the basilar membrane are equally poor at low SPLs and under excellent physiological condition of the cochlea, as indicated by the threshold of the gross cochlear action potential to clicks. The basilar membrane response conforms to the differential cochlear microphonic rather than the much sharper single cochlear nerve−fiber threshold curve. Linearity of response at the peak of the mechanical curve was observed over an 80 dB range: significant nonlinearities were obs...
246 citations
TL;DR: In this article, a simple equation is presented for the dependence of sound speed on temperature, salinity, and depth of water, and a comparison with Del Grosso's NRL II shows discrepancies of the order of tenths of m/sec for realistic values of the parameters.
Abstract: A simple equation is presented for the dependence of sound speed on temperature, salinity, and depth of water. The comparison with Del Grosso’s NRL II shows discrepancies of the order of tenths of m/sec for realistic values of the parameters.Subject Classification: 30.25.
237 citations
TL;DR: In this paper, the Cramer-Rao bound is used to determine an optimum signal processor for passive sonar target range and bearing estimation, where the sonar array consists of an M • element linear array of hydrophone point detectors.
Abstract: Optimum signal processing for passive sonar target range and bearing estimation is discussed for the case where the sonar array consists of an M‐element linear array of hydrophone point detectors whole individual outputs are corrupted by sensor‐to‐sensor‐independent self‐noises of arbitrary power spectra. By comparing the measurement error covariance matrix to the Cramer–Rao matrix bound the system performance, relative to the theoretical optimum, is determined. Further, the Cramer–Rao bound is used to determine an optimum signal processor. The optimum processor is configured as a set of M (M‐1)/2 cross‐correlator delay estimators (one for each hydrophone pair), followed by a Gauss–Markov estimation of the array delay vector (target steering vector), which in turn is followed by a linear weighting of the estimated delay vector elements to determine a bearing estimate and a range estimate. The processor is shown to have the Cramer–Rao matrix bound for its measurement error covariance matrix.Subject Classif...
202 citations
TL;DR: The authors investigated whether the prosodic cue (duration) serves to disambiguate syntactically ambiguous sentences and found that only sentences in which the two meanings were represented by two distinct bracketings were disambigated by durational cues.
Abstract: The present study investigated whether the prosodic cue (duration) serves to disambiguate syntactically ambiguous sentences. An example of one of the ten sentences used is, “The hostess greeted the girl with a smile.” Some of the sentences had two alternative bracketings, e.g.: “The hostess [[greeted] [the girl]] [with a smile],” and “The hostess [greeted] [[the girl] [with a smile]],” while others did not. In this experiment, the duration of certain key words was systematically varied. The groups of words that were varied in this example were: “greeted the” and “girl with a”. The test sentences were presented to subjects who chose between the two alternative meanings. The results indicated that only sentences in which the two meanings were represented by two distinct bracketings were disambiguated by durational cues.
TL;DR: In this paper, a theoretical explanation for photoacoustic spectroscopy is presented, which provides a quantitative foundation for photo-acoustic imaging, and an explicit formula gives the magnitude and phase of the acoustic pressure in terms of the optical, thermal, and geometric parameters of the system.
Abstract: Chopped light impinging on a solid sample in an enclosed cell produces an acoustic signal within the cell, A theoretical explanation for this effect is presented, providing a quantitative foundation for photoacoustic spectroscopy. Nonradiative de‐excitation of the absorbed light within the solid sample produces a periodically varying heat flow from the sample to the surrounding gas and backing material. The solution to the thermal diffusion equations shows that only a thin boundary layer of gas adjacent to the surface of the sample responds thermally to this periodic heat flow. The boundary layer can then be thought of as acting as an acoustic piston creating the acoustic signal detected in the cell. An explicit formula gives the. magnitude and phase of the acoustic pressure in terms of the optical, thermal, and geometric parameters of the system. Simple approximations for the pressure are given according to the relative magnitudes of the optical absorption length, thermal diffusion length, and thickness ...
TL;DR: In this article, exact matrix equations for surface fields, as well as transmitted and reflected wave amplitudes are obtained for an interface having periodic height variation, in conjunction with the extended boundary condition, in which propagating waves are coupled with evanescent modes.
Abstract: Reflection behavior is examined for an interface having periodic height variation. Upon employing the Bloch theorem, in conjunction with the extended boundary condition, exact matrix equations are obtained for surface fields, as well as transmitted and reflected wave amplitudes. Tunneling considerations then lead to new energy constraints for problems of this type, in which propagating waves are coupled with evanescent modes. In the limit of surface corrugations shallow compared with impinging wavelength, analytic results are obtained confirming both the energy constraints and early computations by Rayleigh. Numerical results demonstrate the efficiency of the method.Subject Classification: 20.30.
TL;DR: If identical physical aperture dimensions are used and other parameters held to identical values, the synthetic‐aperture sonar gives higher signal‐to‐ratio than does the nonsynthetic‐aperno sonar primarily because the latter must operate at higher acoustic frequencies for which signal attenuation becomes extremely large.
Abstract: A comparison is made of the signal‐to‐noise characteristics of synthetic‐aperture sonar and conventional sonar. For the synthetic‐aperture sonar case a design procedure is described which makes possible the choice of essentially any unambiguous range and any resolution. Often multiple beam receivers are required. It is shown for the synthetic‐aperture sonar case that the horizontal aperture is the major factor affecting area coverage rate. The comparisons are made with as many parameter values as spossible identical for both the synthetic‐aperture cases and the nonsynthetic‐aperture cases. If identical physical aperture dimensions are used and other parameters held to identical values, the synthetic‐aperture sonar gives higher signal‐to‐ratio than does the nonsynthetic‐aperture sonar primarily because the latter must operate at higher acoustic frequencies for which signal attenuation becomes extremely large. If the sonar systems are operated at the same frequency, then the nonsynthetic aperture sonar can give a higher signal‐to‐noise ratio only when its physical aperture is larger than that used in the synthetic‐aperture case.Subject Classification: 30.82; 60.20.
TL;DR: Forward informational masking is shown to be appreciably smaller than backward or combined informational masks and the threshold change in statistical structure tends to be proportional to the ratio of the durations of the neighboring to the informational sequences.
Abstract: Masking is typically defined in terms of the threshold change in signal level resulting from the presence of a neighboring noise. By contrast with “energetic” masking, informational masking is defined in terms of the threshold change in statistical structure resulting from the presence of a neighboring signal of the same amplitude. Forward masking, backward masking, combined masking, etc., may be defined in terms of the temporal relations of the neighboring to the informational sequences. Forward informational masking is shown to be appreciably smaller than backward or combined informational masking. The threshold change in statistical structure tends to be proportional to the ratio of the durations of the neighboring to the informational sequences.
TL;DR: The formulation described in this paper is aimed at accomodating the nonstationarity more automatically by allowing the linear estimate of the speech signal to be time varying.
Abstract: The efficacy of linear prediction for speech analysis depends upon the degree to which the speech signal is stationary within an analysis interval. For this reason the speech signal is usually divided into small intervals during each of which the signal is assumed to be stationary. The formulation described in this paper is aimed at accomodating the nonstationarity more automatically by allowing the linear estimate of the speech signal to be time varying.Subject Classification: 70.40, 70.65.
TL;DR: The relative importance of VOT as against the presence versus absence of F1 frequency shift after voice onset is assayed in several synthesis experiments in which VOT and F1 configurations are systematically varied.
Abstract: Discussion of voicing as a distinctive property of English stop consonants in initial position has centered on the measure of ’’VOT,’’ the time of onset of laryngeal signal relative to the noise pulse generated by the stop release, but it has been shown that listeners’ selection of ‖b,d,g‖ vs ‖p,t,k‖ responses to synthetic stop+vowel stimuli is not determined entirely by VOT. Significant effects have been reported to depend on the behavior of the first formant (F1) frequency immediately following voice onset, and on this basis it has been suggested that a ’’feature detector’’ responsive to a rapidly shifting F1 better explains the infant’s discrimination of the two stop categories than some mechanism which measures VOT directly. The relative importance of VOT as against the presence versus absence of F1 frequency shift after voice onset is assayed in several synthesis experiments in which VOT and F1 configurations are systematically varied. Labeling data obtained indicate that varying VOT regularly effects a significant change in listeners’ judgments, and that varying F1 has some effect too, but this latter variation is neither necessary nor sufficient generally to shift judgments decisively from one stop category to the other. The data further suggest that the presence of an F1 rising transition after voice onset serves as a voiced‐stop cue not so much because of its dynamic aspect, but simply because its onset frequency is low, i.e., at a value appropriate to a closed or almost closed state of the oral cavity.Subject Classification: 70.30, 70.20, 70.70.
TL;DR: Schroeder et al. as discussed by the authors showed that low-loss, high-scatter surfaces may be required for better concert−hall acoustics Surfaces shaped to give reflection coefficients according to such sequences show the expected high scatter in model experiments with microwavesSubject Classification: 5520, 5540
Abstract: Low−correlation sequences, such as ’’maximum−length’’ and Barker sequences and certain complex (magnitude one) sequences having flat power spectra, are ideally suited for designing surfaces of hard walls with highly diffuse reflections Recent subjective−preference evaluations [M R Schroeder, D Gottlob, and K F Siebrasse ’’Comparative Study of European Concert Halls’’, J Acoust Soc Am 56, XXX−XXX (1974)] indicate that low−loss, high−scatter surfaces may be required for better concert−hall acoustics Surfaces shaped to give reflection coefficients according to such sequences show the expected high scatter in model experiments with microwavesSubject Classification: 5520, 5540
TL;DR: In this paper, a set of equations has been derived to describe the dynamical motions of small cavitation bubbles in liquids set into motion by an acoustic pressure field, taking into account heat conduction inside a bubble and in the surrounding liquid, and the viscosity, compressibility and surface tension of the liquid.
Abstract: A set of equations has been derived to describe the dynamical motions of small cavitation bubbles in liquids set into motion by an acoustic pressure field. The mathematical formulation takes into account heat conduction inside a bubble and in the surrounding liquid, and the viscosity, compressibility, and surface tension of the liquid. The effect of vapor pressure may be determined as a function of the interfacial temperature. The formulation consists of nonlinear ordinary differential, integral, and algebraic equations, and has been programmed for solution on a digital computer.Subject Classification: 25.60; 35.68.
TL;DR: In this article, an arrangement for the puncturing of internal body organs, vessels or the like, through the utilization of a puncturing cannula or hollow needle which will well reflect an ultrasound, as well as an ultrasound-echo sectional view apparatus having an ultrasonic applicator with an ultrasound scanning system for the surface-wide ultrasonic scanning of the body region which is to be punctured, and a display or viewing apparatus for rendering visible the echo-section images.
Abstract: An arrangement for the puncturing of internal body organs, vessels or the like, through the utilization of a puncturing cannula or hollow needle which will well reflect an ultrasound, as well as an ultrasound-echo sectional view apparatus having an ultrasonic applicator with an ultrasound scanning system for the surface-wide ultrasonic scanning of the body region which is to be punctured, and a display or viewing apparatus for rendering visible the echo-section images. On viewing apparatus, a targeting aid for the aiming of a suitable punctuating point in the echo sectional view, and on the ultrasound applicator a guide aide adjustable at least in the targeting direction of the aiming aside for the introduction of the puncturing cannula into the body region which is to be punctured.
TL;DR: The study demonstrated that latency functions are similar to functions derived by loudness−matching procedures in humans: in subjects with normal hearing, equal−latency contours corresponded closely with equal−loudness contours.
Abstract: Reaction time (RT), or response latency, to auditory stimuli has been suggested as a measure of loudness in nonverbal animals as well as in man. In this study RT functions were obtained for human and rhesus monkey subjects under normal conditions and under conditions of hearing impairment. In both humans and monkeys RT varied in a similar manner with changes in intensity and frequency of the stimulus, and in response to experimental manipulation of the receptor organ. The study demonstrated that latency functions are similar to functions derived by loudness−matching procedures in humans: in subjects with normal hearing, equal−latency contours corresponded closely with equal−loudness contours. In subjects with impaired hearing, matched−latency and matched−loudness contours also corresponded closely. Rate of decrease in RT with increasing intensity is discussed and related to rate of growth in loudness. The results suggest that RT is a valuable measure of suprathreshold hearing in human and nonhuman primate...
TL;DR: In this paper, a parametric array in air was conducted using a circular piston transducer which produced spherically spreading, collinear, primary beams at frequencies of 18.6 and 23.6 kHz.
Abstract: An experimental investigation of the parametric array in air was conducted using a circular piston transducer which produced spherically spreading, collinear, primary beams at frequencies of 18.6 and 23.6 kHz. Since source levels were not strong (about 110 dB re 0.0002 μbar at 1 ft), the 5−kHz difference frequency signal generated by the parametric array was relatively weak. Because of space limitations, all measurements were made in the nearfield of the array. Spurious difference frequency signals resulting from intermodulation distortion in the receiving system were suppressed by judicious choice of electronic components and by the addition of an acoustical filter in front of the microphone. The classic properties of the parametric array were observed. The 5−kHz beam was narrow, and no minor lobes were evident. The propagation curve first increased with increasing range, reached a broad maximum, and then gradually decreased. Theoretical predictions were based on a perturbation solution of Burgers’ equat...
TL;DR: Right‐handers tended to perceive the upper tones of the dichotic sequence as emanating from the right earphone and the lower tones from the left, and to maintain this percept when the earphones were places in reverse position, while left-handers as a group did not display the same localization tendency.
Abstract: Ss listened to a dichotic tonal sequence consisting of the repetitive presentation of the C major scale with successive tones alternating from ear to ear. The scale was presented simultaneously in both ascending and descending form, such that when a component of the ascending scale was in one ear, a component of the descending scale was in the other, and vice versa. All Ss channeled this sequence by frequency range: no S channeled by ear of input, and none reported a full ascending or descending scale. Various illusory percepts were obtained, which varied in correlation with the handedness of the listener. Right‐handers tended to perceive the upper tones of the dichotic sequence as emanating from the right earphone and the lower tones from the left, and to maintain this percept when the earphones were places in reverse position. Left‐handers as a group did not display the same localization tendency.Subject Classification: 65.22, 65.54, 65.62; 75.10.
TL;DR: In this paper, a simple analysis predicts the Helmholtz and higher modes of cylindrical resonators, and the analysis requires values of inside and outside orifice end corrections.
Abstract: A simple analysis predicts the Helmholtz and higher modes of cylindrical resonators. Formulas for the quarter‐wave tube, the closed tube, and the classic Helmholtz resonator are special cases. It is found that the classic Helmholtz formula begins to lose accuracy for resonator lengths L≳λ/16. A corrected Helmholtz equation is given as an approximation to the exact result. The analysis requires values of inside and outside orifice end corrections. Rayleigh’s model of a piston in an infinite wall and Ingard’s calculations for a piston radiating into a tube give satisfactory results when the theory is compared to experiments. Resonator experiments were performed with k0L in the range π/8 to 3π/8 and orifice to cavity diameter ratios from 0.1 to 0.8.Subject Classification: 20.40.
TL;DR: A mathematical formalism developed for investigating the dynamics of cavitation bubbles has been used to obtain numerical solutions describing the behavior of bubbles of different initial radii that are damped by heat conduction, viscosity, and compressibility as mentioned in this paper.
Abstract: A mathematical formalism developed for investigating the dynamics of cavitation bubbles has been used to obtain numerical solutions describing the behavior of bubbles of different initial radii that are damped by heat conduction, viscosity, and compressibility. Calculations have been made to determine two measures of damping, the maximum temperatures, the maximum pressures, and the resonance frequencies of bubbles set into pulsations by a pressure pulse. In general, these quantities are controlled by heat conduction and viscosity at small amplitudes and mainly by compressibility at large amplitudes of motion. One measure of damping—the energy dissipation modulus—has a peak at a well‐defined maximum radius. This peak serves to define a transition radius; for pulsations with amplitudes greater than this transition radius, the fraction of available energy dissipated in a cycle decreases and hence very large internal energy densities may occur. A second transition occurs at a radius called the critical radius...
TL;DR: In this paper, a closed-form asymptotic expression for the frequency wavenumber dispersion relation for the fundamental and odd overtone thickness−shear branches near cutoff is obtained from the three-dimensional linear equations.
Abstract: Electroelastic equations containing terms up to cubic in the small mechanical displacement field, but no higher than linear in the electric variables, are applied in the analysis of intermodulation in rotated Y−cut quartz oscillators. Both pure thickness−shear vibrators and essentially thickness−shear trapped energy resonators are treated. In the linear part of the analysis of the trapped energy resonator, a closed−form asymptotic expression for the frequency wavenumber dispersion relation for the fundamental and odd overtone thickness−shear branches near cutoff is obtained from the three−dimensional linear equations. Lumped parameter representations of the solutions, which are valid in the vicinity of a resonance, are presented for the linear and nonlinear portions of both the pure thickness−shear and trapped energy thickness−shear problems. The influence of the driving and detecting circuitry is included and, in particular, in each case the relation between the intermodulation and driving voltage is obt...
TL;DR: Physical measurements of the transfer function from a free−field sound source to a microphone in the subject’s ear canal indicate that there are two independent localization cues generated by the pinna and both are used by subjects in vertical localization tasks.
Abstract: Physical measurements of the transfer function from a free−field sound source to a microphone in the subject’s ear canal indicate that there are two independent localization cues generated by the pinna. For sound sources in the vertical median plane, there is a systematic change in the frequency response as a function of elevation angle, and a disparity between the left−ear and right−ear responses which also changes systematically with elevation angle. Independent psychophysical measurements indicate that these pinna cues are detectable by subjects, and both are used by subjects in vertical localization tasks.Subject Classification: 65.62, 65.75.
TL;DR: It is suggested that in monkey, as in man, a relation exists between speaking and hearing: both man and monkey will increase voice amplitude in the presence of masking noise of the appropriate spectral composition.
Abstract: Old World monkeys (Macaca) were trained to vocalize at a steady rate in the laboratory by the use of operant conditioning techniques with food as a reinforcer. While the animals were vocalizing, they were subjected to one of two noise bands (200–500 Hz or 8–16 kHz) at different sound pressure levels (70, 80, and 90 dB SPL). Vocal amplitude was measured as a function of the SPL of the noise bands. The monkeys increased voice amplitude to the band of low‐frequency noise but not to the high‐frequency band. These results suggest that in monkey, as in man, a relation exists between speaking and hearing: both man and monkey will increase voice amplitude in the presence of masking noise of the appropriate spectral composition. Subject Classification: 65.22; 70.20.
TL;DR: In this paper, a numerical technique based on the finite-element method has been developed for analyzing the performance of systems of acoustic elements including expansion chambers in mufflers, which can be applied to any system component with arbitrary boundary geometry provided this may be realized by an assembly of rectangular elements.
Abstract: A numerical technique based on the finite−element method has been developed for analyzing the performance of systems of acoustic elements including expansion chambers in mufflers. The theories developed are, firstly, the variational formulation of the acoustic field existing in the system and, secondly, the finite−element approximate solutions of the variational problems. The predictions of transmission loss are then made by forming the equivalent acoustic four−terminal transmission network in which the acoustic four−pole constants are calculated from the finite−element method. As used, the finite−element approach is perfectly general and may be applied to any system component with arbitrary boundary geometry provided this may be realized by an assembly of rectangular elements. The method is applied to simple expansion chamber models because the results are tractable and theoretical results from acoustic filter theory are available for comparison purposes. The comparison brings out an important fact: the accuracy of the prediction of transmission loss implies that the variational formulation and finite−element approximations are adequately applicable to a number of practical applications.Subject Classification: 50.40; 20.40.
TL;DR: A sonar system for generalized target characterization is described and a physically meaningful generalization is obtained by modeling an impulse response in terms of pulse doublets, impulses, step functions, ramp functions, etc.
Abstract: Range‐distributed targets are often characterized arrays of point scatterers. This conceptualization corresponds to a target impulse response that is a sequence of impulses. A physically meaningful generalization of this description is obtained by modeling an impulse response in terms of pulse doublets, impulses, step functions, ramp functions, etc., i.e., as a superposition of delayed impulses and differentiated or integrated impulses. The resulting impulse response model resembles a spline function without continuity conditions. A sonar system for generalized target characterization is described; signals and receivers are specified for (1) optimum estimation of reflector parameters and (2) detection of a known target in clutter. The derived signals correspond closely with some of the waveforms that are used by dolphins and bats for echolocation. The corresponding echo analyzers are similar to some psychoacoustic models of the mammalian hearing system.