bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated field measurements without use of an external computer for the control of instrumentation
Authors: Carlsen Thor , Ese Gustav
Published: October 2005

Computer control over different measurement problems has in the past years become more and more popular. Computers have decreased in size and weight, while the software capacity has increased several times. However, using such a system in the field still requires that the necessary computer is brought, along with the instrumentation, to the field to make the measurements. This paper discusses a new precision sound measuring instrument (that is available also as a retrofit) with an internal BASIC software programming facility. This feature allows customized measurement sequences, calculation of final and intermittent results, control of other instruments, and graphical presentations to be carried out directly in the field on the internal video display unit without the need of an additional external computer. Descriptions of practical applications such as sound intensity, spectrum shaper control, and building acoustics measurements are also included.
Perceptual restoration of music
Authors: DeWitt Lucinda A. , Samuel Arthur G.
Published: October 2005

A number of studies have investigated the perceptual restoration of deleted speech sounds. The present study explored a musical analog to the speech case. Several experiments investigated whether or not listeners restore notes that have been deleted and replaced by matched white noise. The experiments used Samuel's [JEP: General 110, 474–494 (1981)] “added-replaced” methodology to separate perceptual restoration from any higher level decision factors. In one experiment, we compared restoration of phonemes in words and notes in faimilar melodies; a single-note control condition was also run. Using the measure of percpetual restoration, words produced stronger restoration of their components than melodies did; the melodies produced stronger restoration than the controls. In other experiments, we have investigated the role that familiarity plays in perception of melodies, and the influence of melodic and rhythmic structure. We will consider the implications of the results for theories of speech and music perception. [Work supported by AFOSR and NSF.]
Effects of lexical stress placement on auditory word recognition
Authors: Slowiaczek Louisa M.
Published: October 2005

Research was conducted examining the role of lexical stress in auditory word recognition. In a series of experiments, isolated spoken words were presented to subjects with correctly produced stress pattern (CS) or incorrectly produced stress pattern (IS). In three separate experiments subjects were asked to identify the CS and IS items in varying amounts of white noise, make a lexical decision or monitor for any items that were nouns. The results revealed no effect of stress replacement on identification of words in noise, but revealed a significant effect of stress placement on lexical decision and noun monitoring response times. The role of lexical stress information in auditory word recognition will be discussed in light of these results. [Work supported by NIH.]
Constant beamwidth receiving arrays for broadband detection and power estimation of signals
Authors: Lardies Joseph , Flenner Jean-Pierre
Published: October 2005

The detection at low frequencies and power estimation of broadband signals may often be accomplished with an array of sensors. Four beamformers are studied; the conventional end-fire beamformer, and the maximum-likelihood estimator, the maximum-entropy estimator, and a new broadband constant beamwidth beamformer. It is shown that it is impossible to detect and estimate the power of small signals at low frequencies by the conventional end-fire array, by the maximum-likelihood, or by the maximum-entropy methods. An algorithm with superior low-frequency performance is studied. The proposed method estimates the signal powers from the correlation between sensors. We find that the beamwidth of the processor is remarkably insensitive to frequency variations and is under operator's control. This technique may detect and estimate the power of signals, at low frequencies, which could not be found using the other techniques.
Sensitivity of the matched-field source localization technique in shallow water to mismatch of geoacoustic parameters
Authors: Del Balzo Donald R. , Feuillade Christopher , Rowe Mary M.
Published: October 2005

The accuracy of matched-field techniques for source localization in a shallow-water waveguide is dependent upon realistic modeling of the geoacoustic environment. A study was conducted to investigate the sensitivity of source localization to erroneous estimates of the geoacoustic properties (sound speed, density, and attenuation) of the sediment. A range-independent normal-mode computer program was used to calculate acoustic fields from a midwater source received on a vertical array of 21 hydrophones spanning the water column. Errors in estimates of range and depth are presented as a function of mismatch of each geoacoustic property.
A study of bathymetric scattering using simulation techniques
Authors: Baer R. N. , Perkins J. S. , Berman D. H.
Published: October 2005

Seafloor scattering can significantly affect the acoustic field. The statistics of ocean floor scattering were simulated by using the split-step parabolic equation with an ensemble of possible bathymetries in a manner analogous to that of Tappert and Nghiem-Phu [J. Acoust. Soc. Am. Suppl. 1 77, S102 (1985)]. The bathymetry was taken to have a Gaussian spectrum. Situations with various horizontal correlation lengths and rms roughness were examined. Different acoustic sources were also considered. An ensemble of 100 to 200 parabolic equation runs was found that in general was sufficient to give predictions of the mean and standard deviations of the acoustic field. The ensemble-mean distribution differs significantly from both an individual ensemble member and field with the average (flat) bathymetry. In the convergence zone, the variance of the acoustic field correlates with the mean transmission loss and it decreases with decreasing rms roughness or increasing horizontal correlation length. Outside the convergence zone, the variance is high even for relatively smooth cases. [Work supported by NRL and ONR.]
An nth order solution of the Neumann series in scattering from rough interfaces
Authors: Werby M. F. , Keiffer Richard
Published: October 2005

Scattering from rough interfaces has been treated by the integral representation of the Helmholtz equation. This equation involves surface integrals and is well suited for rough interfaces which are piecewise continuous. The well-known Kirchoff approximation involves replacing the unknown surface pressure field and its gradient by the incident field as a first-order approximation to the integral equation. This leads to an expression which involves direct integration and will be noted to represent the first term in the Neumann solution of an integral equation of the second kind. Physically, it corresponds to one encounter of the field with the interface. It can be shown that the nth solution corresponds to n encounters with the interface. We derive expressions for the nth solutions of the Neumann series. The expressions are exact for each order for the three-dimensional case and include an out-of-plane scatter.
Sound propagation through random currents using parabolic approximations
Authors: Brent R. I. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

The influence of random, horizontal, depth-dependent ocean currents in the parabolic approximation is studied. Emphasis is placed on received acoustic intensity. Parabolic equations including currents, derived recently by our group, are examined using perturbation and asymptotic methods. Expressions are derived for the mean and standard deviation of intensity. The development assumes that the random current is wide-sense stationary. For convenience, an exponential-cosine autocorrelation function with depth is taken, although any such function can be used. Formulas obtained are sufficiently general to permit many types of depth-dependent sound speeds and bottom interface models. We illustrate current fluctuation effects on intensity moments for the specific case of an isospeed channel with a perfectly hard bottom. The acoustic consequences of changes in physical parameters directly related to current fluctuations, such as its standard deviation and correlation length, are discussed. Also exhibited are changes in random current effects on intensity which result from changes in noncurrent related parameters, such as acoustic frequency and channel depth. [Work supported by ONR.]
Vibration properties of the pipa. A Chinese musical instrument
Authors: Chen Qing-hua , Yang Jien-ping
Published: October 2005

The pipa is an ancient Chinese musical instrument similar to a lute. Its origin can be traced back 2000 years. It has been referred to as an Oriental guitar. This paper presents the results of theoretical and experimental studies of the vibration properties of a pipa. The spectrum of the sound produced is shown for different playing techniques, playing angles, and playing positions. Sound spectra are related to vibrational modes of the instrument.
Advances in the application of sound intensity techniques to the determination of the noise emission of machines
Authors: Maling George C.
Published: October 2005

The advances that have been made in the last 50 years in the application of sound intensity techniques to the determination of sound power are reviewed. The early development of sound intensity meters or “acoustic wattmeters” by Olson, Clapp, and Firestone and Schultz are presented, and the development of modern instruments is reviewed. In the early 1970s sound intensity methods were used for the determination of sound power, and improvements in the methods have been made in the last 12 years. In this paper, the effects of background noise and the selection of microphone positions will be discussed, and the progress that has been made in the development of Standards which may be used for the determination of sound power will be presented.
Application of nearfield acoustical holography to infrasonic noise source determination
Authors: Gan W. S.
Published: October 2005

In my previous paper (W. S. Gan, paper presented at the 1st Congresso Brasileiro de Acustica, Brasil, Feb. 1979), we apply acoustical holography to the determination of infrasonic noise source with the experimental setup using a correlation filtering approach. In this paper, we apply acoustical holography to the same problem, but with the experimental setup using the nearfield acoustical holography (NAH) [E. G. Williams and J. D. Maynard, Phys. Rev. Lett. 45, 554–557 (1980)] which can overcome the resolution problem. Infrasonic frequencies are even more appropriate for NAH than are audio frequencies due to the very long wavelengths involved. We propose the use of array processing since the experimental setup will involve large number of microphones (sensors). Array processing will speed up the calculation of FFT and Green's function. It permits the simultaneous processing of the data from each sensor. We derive the Green's function and the expression for the holographic reconstruction from the Bojarski's exact inverse scattering theory [N. N. Bojarski, Radio Sci. 16, 1025 (1981)]. An exact closed-form analytic solution for the infrasonic noise source term is obtained.
Using hearing conservation data to study the epidemiology of noise-induced hearing loss
Authors: Erdreich J. , Erdreich Linda S.
Published: October 2005

Annual audiometric testing mandated by Federal Regulations is creating an enormous, fragmented database. Epidemiologic studies, based on this information, can potentially elucidate important parameters related to the development of noise-induced hearing loss. This paper illustrates the application of survival data analysis to the audiometric data of approximately 2500 people taken over as many as ten successive years. Survival analysis includes both the number of people who fail during a study (develop a standard threshold shift in this instance) as well as those who survive or are lost to follow-up. In this case, we found that the survival function (the probability of surviving past a time interval) and the hazard function (the probability of surviving through a time interval given that the worker has survived to the beginning of the interval) are insensitive to the exposures at the facility. However, when these functions are stratified on age at first test, older workers are at higher risk than younger workers.
An acoustical shape optimization study of the nonrectangular reverberation room
Authors: Milner Joseph R. , Bernhard Robert J.
Published: October 2005

A computationally efficient technique for the low-frequency acoustic optimization of nonrectangular reverberation rooms is discussed. The technique utilizes the finite element shape optimization procedures discussed by Bernhard and Milner [R. J. Bernhard and J. R. Milner, “Acoustic shape optimization using the finite element method,” J. Acoust. Soc. Am. Suppl. 1 79, S51 (1986)]. Triangular regions are shown to have properties allowing modal reductions, resulting in reduced eigen-systems which afford a dramatic decrease in computational effort. By utilizing these triangular regions, the nonrectangular reverberation room may be globally optimized in an economical fashion. Results are presented using performance criteria similar to that of Louden [M. M. Louden, “Dimension ratios of rectangular rooms with good distributions of eigen-tones,” Acustica 24 (1974)]. The character and optimal solution to the rectangular reverberation room is shown. Optimal solutions to nonrectangular rooms with various allowable room configurations are also shown.
Sound amplification from controlled excitation reactions (SACER) in N2/He and N2/CH4 mixtures
Authors: Shields F. Douglas , Lafleur L. Dwynn
Published: October 2005

Last year, the discovery of SACER in N2/H2 mixtures was reported [J. Acoust. Soc. Am. Suppl. 1 78, S45 (1985)]. This paper discribes similar measurements in N2/He and N2/CH4 mixtures. Sound amplification has been observed, and its dependence upon gas pressure, sound frequency, foreign gas concentration, and vibrational temperature is that generally expected from a crude relaxation model for the gases and published values of the relaxation times. However, as in the case with N2/H2 mixtures, the gain is an order of magnitude bigger and persists longer than expected. An electrical discharge was passed through the gas to initiate the acoustical oscillations and elevate the vibrational temperature. In N2/CH4 mixtures, the gain and the nature of the electrical discharge were found to depend on the number of times the discharge was passed through the gas. This result is interpreted as being due to a chemical reaction between N2 and CH4 that produces an impurity that shortened the relaxation time. [Work sponsored by the ONR.]
Vibrational-vibrational coupling in air at low humidities
Authors: Zuckerwar Allen J. , Miller Keith W.
Published: October 2005

Calculations of sound absorption in air are traditionally based on the assumption that molecular relaxations in nitrogen and oxygen are independent. In binary mixtures of these two gases, however, molecular relaxation is known to be controlled by a very strong vibrational-vibrational (V-V) coupling, which influences both the relaxation times and the relaxation strengths. This presentation addresses the question of whether small concentrations of the air constituents carbon dioxide and water vapor, which themselves possess a strong V-V coupling to N2 and O2, serve to decouple the N2 and O2 relaxations. A “coupling strength” is derived, which depends upon the constituent concentrations and the related reaction rate constants. It is found that the molecular relaxations associated with N2 and O2 in air experience a gradual transition from strong to weak coupling as the humidity increases beyond approximately one part per million.
Comparison of constrained layer damping models
Authors: Fausett Donald W. , Fausett Laurene V. , Dubbelday Pieter S.
Published: October 2005

The constrained layer damping technique is based on the application of a layer of viscoelastic material onto the surface to be damped and beneath a layer of stiff material. The damping mechanism is dissipation of energy caused by shear motion in the damping layer. An early model for the propagation of straight-crested waves in a constrained plate by Kerwin [J. Acoust. Soc. Am. 31, 952–962 (1959)] uses thin-plate theory for the base plate and is limited to flexural waves. This model was extended to cover extensional as well as flexural waves in thick plates by describing the base plate by exact elasticity theory [P.S. Dubbelday, J. Acoust. Soc. Am. 80, 1097–1102 (1986)]. The present study proposes the formulation of a model based on exact elasticity theory for all three layers. A computer program based on the exact equations for the case of an infinite composite plate in vacuum has been developed. It is used as a basis for comparison of results from previous models and to investigate certain anomalies in the calculated results of those models. [Work supported by the ONR.]
Viscoelastic versus radiation damping in fluid-loaded constrained plates
Authors: Dubbelday Pieter S.
Published: October 2005

A hybrid model was developed for the analysis of constrained-layer damping whereby the base plate is described by exact elasticity theory, while the elastomer and constraining layers are analogous to Kerwin's model [J. Acoust. Soc. Am. 31, 952–962 (1959)]. Under fluid loading, the success of the technique is measured by a damping efficiency, the ratio of loss in the elastomer to the total loss due to viscoelastic and radiation damping. This efficiency is usually evaluated by combining the viscoelastic loss from a composite plate in vacuum, for antisymmetric and symmetric waves separately with the radiation loss from a single fluid-loaded plate. This assumes simple addition of the two effects for a fluid-loaded constrained plate. Extension of the hybrid model to include fluid loading shows that at higher frequencies the presence of the two types of waves redistributes the energy across the plate, invalidating the presumed additive property. Thus it proves necessary to compute damping efficiency from analysis of the fluid-loaded composite plate with inclusion of both antisymmetric and symmetric waves. [Work supported by the ONR.]
Damping of acoustic waves in bcc crystals
Authors: Kailash  , Shanker Kiran
Published: October 2005

The study of damping of acoustic waves is made in bcc crystals from 50–500 K at zero magnetic field. The theory is developed from primary physical constants; nearest-neighbor distance and hardness parameter; and basic potentials: electrostatic and Born-Mayer. The cesium halides are studied acoustically along different directions of propagation and orientation. The molecular weight, temperature, frequency, direction of propagation, and orientation dependence are explained, and it is stated that damping is the characteristic property of substance.
Damping of elastic waves in metallic alloys
Authors: Shanker Kiran , Kailash
Published: October 2005

Starting from the nearest-neighbor distance and repulsive parameter and using Coulomb and Born-Mayer potentials, the theory is developed for damping of elastic waves in metallic alloys. The study is made in nickel-copper alloys for different compositions over a wide temperature span. It is observed that the damping follows the Tn law, where n is an exponent. It is concluded that damping is the fundamental property of the substance.
The effect of combinations of continuous and impact noise on the auditory system: Energy considerations
Authors: Ahroon William A. , Hamernik Roger P. , Salvi Richard J.
Published: October 2005

Fifty-three chinchillas completed an experimental paradigm designed to study the interaction between a low-frequency octave band of noise and three levels of impact noise whose parameters were balanced to produce exposures having approximately equal energies. The animals were exposed to one of the following seven conditions: (1) 0.5 kHz C.F. octave band @ 95 dB SPL for 5 days; (2) 113 dB peak SPL impact noise, 1/s for 5 days; (3) Combination of 1&2; (4) 119 dB peak SPL impact noise, 1/4 s for 5 days; (5) Combination of 1&4; (6) 125 dB peak SPL impact noise, 1/16 s for 5 days; (7) Combination of 1&6. Pre- and post-exposure estimates of threshold were obtained using evoked auditory potentials recorded from a chronic electrode implanted in the area of the inferior colliculus. Status of the sensory cell population was evaluated using surface preparation histology. The three energy balanced “impulse-alone” exposure conditions produced very similar levels of ATS, PTS, and sensory cell loss indicating that the exposure energy is a critical variable for predicting the consequences of such exposures, However, the three combination exposures produced results which differed across the three groups with the 119- and 125-dB combination conditions producing a significantly increased level of acoustic trauma. The results of the combination exposures, cast doubt upon the general validity of the equal energy concept. [Work supported by NIOSH.]
Temporary auditory-threshold shifts induced by exposures to continuous tones in water
Authors: Smith Paul F.
Published: October 2005

Four bare-headed divers were exposed for 25 min to continuous tones in water at frequencies of either 700, 1400, or 5600 Hz at average sound pressure levels (SPL) between 143.1 and 165.1 dB above 20 μPa. These SPL are comparable to those produced by some underwater hand-held tools. These conditions yielded individual temporary auditory-threshold shifts (TTS) between 23 and 55 dB 2 rain post-exposure. Recovery required up to 50 h or more depending on exposure conditions. Nonauditory effects including middle-ear sensations and a reddened ear drum were also observed. Four additional divers were exposed successively for 10-min periods to pure tones of 5600, 1400, and 700 Hz (in that order) in air at 100 dB and in water at various SPL between 125 and 150 dB. Divers incurred moderate TTS from all exposures. For equivalent intensities in air and in water, 700-Hz exposures produced equivalent TTS. Less TTS was induced in water at 1400 Hz; more TTS in water at 5600 Hz. The results suggest that, within the predictive accuracy of the TTS technique, several hand-held tools now in use by military and civilian divers are extremely hazardous to hearing.
Amplitude versus frequency modulation in speech perception
Authors: Bunnell H. T. , Pickett J. M.
Published: October 2005

Remez et al. [Science 212, 947–950 (1980)] presented stimuli consisting of three tones that were simultaneously frequency and amplitude modulated to follow variations in the frequencies and amplitudes of the first three formants throughout an utterance. Bunnell [J. Acoust. Soc. Am. Suppl. 1 75, S85 (1984)] presented speech consisting of five amplitude modulated tones at fixed frequencies 1000 Hz apart. Both types of stimuli represent a severe reduction of speech information, however, one might expect that stimuli like those used by Remez et al., because they more clearly represent formant frequency variations over time, would provide better information for phonetic perception. To directly compare these two stimulus types, nonsense utterances of the form /əCalə/ (C = {/b/,/d/,/g/}) were synthesized using natural productions as templates. In one condition (FM), tokens consisted of four tones which followed the frequencies of the first four formants. In the other condition (AM), stimuli consisted of tones at 500, 1500, 2500, and 3500 Hz which were independently modulated in amplitude to follow variations in the utterance's spectrum level at those frequencies. The stimuli were presented to listeners in a three-alternative stop consonant identification task both with and without added broadband noise. Results suggest that, with some constraints, AM tokens supported stop consonant identification at least as well as their FM counterparts.
Auditory confusion of whispered plosives
Authors: Chen Hsiao-Chuan , Nábělek Igor V.
Published: October 2005

Ten normal-hearing subjects listened to a recorded list of 120 whispered consonant-vowel syllables spoken by a male talker. The consonants were six plosives /b,p,d,t,g,k/, the vowel was /a/. Each syllable was repeated 20 times in random order. The overall consonant identification score was 85.2%. The scores for the voiced consonants were lower than for the voiceless ones, but they were still rather high. The highest average identification score of 96% was obtained for /k/. The average scores were 91%, 88.5%, 83%, 81%, and 71.5% for /t/, /d/, /p/, /b/, and /g/, respectively. A pairwise comparison showed that the difference between /k/ and /g/ scores was significant. With respect to place, alveolars and bilabials had the highest and the lowest scores, respectively. Whispered /b,d,g/ were more often confused with their cognates than vice versa; cognate errors were more numerous than place errors. These results indicate that the voicing contrast is indeed useful for distinguishing voiced and voiceless plosives, however that there are other cues which allow the discrimination between voiced and voiceless consonants if the voicing contrast is absent.
Formantless vowels and theories of vowel perception
Authors: Gooding Frank
Published: October 2005

Most theories of vowel perception rely on a stage of formant peak extraction. However, combining the indications from earlier studies with single formant vowels [Chistovich and Lublinskaya, Hear. Res. 1, 185–193 (1979)] and formantless vowels with “flat” spectra [Carpenter and Morton, Lang. Speech 5, 203–214 (1962)], it would appear that perceived vowel quality does not depend on extraction of two or more formant peaks. In this study, Carpenter and Morton's results are extended by constructing a series of tones with “step” spectra with F0 (125 Hz) represented by the first harmonic. It was discovered that a full range of clear, satisfactory front vowel qualities ([i] to [a]) resulted with a band of high-frequency harmonics, where the upper frequency cutoff was 3.5 kHz, and the low-frequency edge varied from 3-1 kHz. Similarly, a back vowel series could be created with a low-frequency band consisting of the first two to the first nine harmonics. The results are interpreted in terms of gross spectral dominance as a prime determinant of phonetic vowel quality. Further experiments with formant and formantless vowels are planned to test this hypothesis.
Categorical perception of speech intonation contour: The psychoacoustic basis of tonetic categories
Authors: Faulkner Andrew
Published: October 2005

The notion of perceptual categories for intonation contour has particular attractions in speech recognition and speech synthesis. According to the logic of categorical perception, tonetic category boundaries should correspond to discrimination peaks. Can such peaks be found, and if so, is their basis speech-specific or psychoacoustic? A series of ABX experiments will be reported that examine discriminability along stimulus continua formed by one- and two-section logarithmic f0 slopes, imposed on both synthetic speech, and complex tone stimuli. A single discrimination peak was found, for both speech and tone stimuli, in the region of a flat f0 slope. This discrimination peak corresponds to a putative category boundary which could distinguish rise from fall contours, on a one-section slope, and distinguish fall from fall-rise contours, on a two-section slope. Because the same discrimination peak is evident for speech and non-speech stimuli, the basis of the category boundary effect can be regarded as psychoacoustic.
Some concepts in the statistical energy analysis
Authors: Maidanik G.
Published: October 2005

In a recent presentation an attempt was made to introduce basic concepts in the development of the elements of the statistical energy analysis (SEA). [G. Maidanik, J. Acoust. Soc. Am. Suppl. 1 79, 511 (1986)]. The analytical definitions and manipulations were exercised on a simple dynamic system so that they could not clutter unduly the conceptual understanding of SEA. Moreover, although SEA is devised to deal mostly with the dynamic behavior of interacting structural system, many of the basic concepts that underlie SEA can be explained and understood employing a single noninteracting dynamic system. The modal approach was used and the division of the energy stored in the dynamic system into a resonant and a nonresonant part was derived. The significance of this division was briefly discussed. This paper discusses more recent concepts such as the division of stored energy into a direct and a reverberant part.
Transient and steady-state target resonance vibrations extracted from their acoustic echoes
Authors: Gaunaurd G. C. , Tsui C. Y.
Published: October 2005

Scattering experiments carried out decades ago [W. Angeloff and F. Abbot, NEL TR-1273 (Mar. 1965)] are examined in the light of modern theoretical advances. This places the early observations on solid theoretical foundations and permits a reliable and understandable measurements program. This description is achieved by the suitable sampling and processing of the returned signals. It was found that pulses backscattered from targets are-divided into three parts, an initial transient region, a steady-state region, and a final transient regime corresponding to the re-radiation of the stored energy by the structure. If the backscattered pulse is sampled in the steady-state or free-vibration region, one obtains the usual backscattering cross section of the body. However, if the sampling is done within the final transient regime, near the tail end of the pulse, then the “backgrounds” of the resonance scattering theory (RST) are automatically suppressed and one obtains, experimentally, the “spectrogram” of the body, with its modal resonances completely isolated. In this case, if one sweeps the angle θ around the body with the frequency fixed at the value of any resonance frequency, one then obtains “rosetta” patterns, which yield graphic multipole interpretations of the resonant modes excited. Theory and experiments match well, and we exhibit many examples.
Orthogonal polynomial compression amplification for the hearing impaired
Authors: Levitt Harry , Neuman Arlene C. , Toraskar Jayashree
Published: October 2005

The method of orthogonal polynomials is a computationally concise curve-fitting technique [Levitt and Rabiner, J. Acoust. Soc. Am. 49, 569–582 (1971)]. Each coefficient in the polynomial expansion is obtained using a single vector operation. The computational simplicity of the procedure allows for real-time speech processing using a digital master hearing aid configured around a MAP-300 array processor. The short-term spectrum of speech is first approximated by a set of orthogonal polynomials and then modified by compressing the range of variation of the polynomial coefficients. Compression of the constant term is analogous to conventional amplitude compression. Compression of the linear coefficient reduces variations in the slope of the short-term spectrum. Compression of the quadratic coefficient reduces variations in convex/concave curvature. Implementation in real time allowed for a paired-comparison adaptive strategy to be used in searching for the optimum set of compression coefficients for each subject. Compression of the constant term was found to have the largest effect leading to a significant improvement in the dynamic range of the performance-intensity function for a group of hearing impaired subjects. [Research supported by NINCDS.]
A new model of wall pressure fluctuations
Authors: Witting James M.
Published: October 2005

Recent work has led to a new spectral model for pressure fluctuations at a rigid plane wall bounding a turbulent boundary layer, based on an explicit representation of structures in the boundary layer near the wall—bursts and sweeps—that exchange momentum within the layer and support the shear stress there [J. M. Witting, Noise Control. Eng. J. 26, 28—43 (1986)]. The fluctuating wall pressure results from the contributions of a collection of independent bursts and sweeps. Each burst and sweep is modeled as a dipole flow that moves with the local mean flow, has a finite duration, and has the correct strength to mix the fluid through a Prandtl mixing length above and below its center. This paper describes some of the salient features and extensions of the model, emphasizing (1) the physical interpretation of the model structure and its three adjustable parameters, which are sufficient to yield predictions for all frequencies and wavelengths, (2) the ranges of frequencies and wavenumbers over which the model can be applied with confidence, based both on theory and past experiments, and (3) the applicability of the modeling approach to other situations.
Analytical structural acoustics of submerged cylindrical shells
Authors: Harari A. , Sandman B. E.
Published: October 2005

A detailed analytical model of ring-stiffened cylindrical shell vibration is presented. The model is to accept excitation due to turbulent boundary layer pressure fluctuations. The mathematical model is capable of predicting the acoustical effects of a compliant decoupling layer attached to the external surface of the shell structure. Both the shell vibration levels and farfield acoustic pressures are predicted. A few focused example results are presented with and without acoustical decouplers.
Wall pressure measurements and acoustics in turbulent pipe flow
Authors: Daniels Mark A. , Lauchle Gerald C.
Published: October 2005

Measurements of the turbulent boundary layer (TBL) wall pressure spectrum and acoustic field were conducted in the Boundary Layer Research Facility of the Applied Research Laboratory. This facility uses glycerine as the working fluid. Subminiature, piezoresistive pressure transducers were used for these measurements. The TBL wall pressure spectrum was obtained using a novel signal processing technique (transducer difference signals) that minimized both acoustic and vibration-induced noise while maintaining the integrity of the measured TBL wall pressure spectrum. A measurement involving the coherence function between these transducer difference signals validated the measured TBL wall pressure spectra and all assumptions used in the development of the measurement technique. The measured nondimensionalized spectra of the TBL fluctuating wall pressure are compared to those measured in previous investigations. These comparisons have substantiated a maximum, normalized transducer diameter for the complete resolution of the high-frequency spectral energy associated with the pressure fluctuations within the TBL. In this investigation, a transducer diameter of 2.1 viscous wall units is demonstrated. This is a factor of 9, smaller than ever before achieved. [Work supported by Applied Research Laboratory E/F Program under NAVSEA contract.]
Fluid loading on vibrating plates in a uniform flow field via a wave-vector/time domain method
Authors: Li Dong-Jye , Stepanishen Peter R.
Published: October 2005

A new approach is presented to evaluate the fluid loading on vibrating elastic plates with specified time-dependent velocities in uniform flows. An in vacuo eigenfunction expansion with time-dependent coefficients is used to describe the specified normal velocity of the plate. Acoustical fluid loading on the plate is expressed as an eigenfunction expansion in which each modal coefficient is expressed as a summation of convolution integrals involving fluid/modal impulse responses and the modal velocities coefficients. Wave-vector/time domain methods are used to develop expressions for the fluid modal impulse responses. Numerical results are presented to illustrate the characteristics of the fluid/modal impulse responses and fluid loading for various plates and Math numbers. (Work supported by ONR.]
Plumbing noise measurement and isolation
Authors: Christoff Jerry P.
Published: October 2005

Plumbing noise measurements on valves used for domestic lavatories, showers, tubs, and toilets have been measured utilizing the approach outlined in ISO Standard 3822. This technique evaluates the flow induced structural vibration transmitted into the piping system. The results clearly indicate that the principal source of noise is turbulence within the valve mechanism and not due to excessive velocities in the piping. Comparisons will be provided between American and European products. Several standard methods of isolating pipe wall vibration from building components are also evaluated.
Discovering acoustic features with a connectionist learning algorithm
Authors: Elman Jeffrey L. , Zipser David
Published: October 2005

A method for discovering acoustic features in speech using a parallel distributed processing (or “connectionist”) learning algorithm is described. The approach involves representing speech patterns as distributed patterns of activation over a network of interconnected processing elements. The “generalized delta rule” (Rumelhart, Hinton, and Williams, 1986) is used to teach the model to autoassociate various speech patterns with themselves. Teaching is accomplished by adjusting connection strengths between processing elements in order to minimize the error in autoassociations. This method was used to discover a set of acoustical features which efficiently and accurately encode speech sounds. The results of several simulations are reported, and the implications of the approach for models of human speech perception, as well as possible applications for machine-based speech recognition systems are discussed. [Work supported by the Office of Naval Research.]
Effect of the spectral model order in automatic speech recognition
Authors: Tsuga Kazuhiro , Hermansky Hynek
Published: October 2005

It has been observed that in speaker-independent multi-template digit recognition, the 5th-order perceptually based LP (PLP) analysis method yields about 40% lower error rates than does the standard 14th-order LP. In speaker-dependent recognition, the 5th-order PLP model yields essentially the same recognition accuracy as do high-order PLP or standard LP models. In order to clarify the reasons for this result, RPS distances for LP and PLP models of single-frame phoneme-like spectra of male and female speakers were computed and arranged into distance matrices. Single-speaker 10th-order model matrices were adopted as the reference matrices for both LP and PLP methods. Cross-speaker PLP matrices become more similar to PLP reference matrices as the model order of cross-speaker matrices decreases to the 4th order. LP cross-speaker matrices remain relatively similar to the 5th order. Single-speaker PLP matrices remain relatively similar to the 5th order of the model while the single-speaker LP matrices of lower order differ significantly from the high-order ones. These results agree well with recognition rates obtained in the cross-speaker alpha-digit recognition for the same speakers. Results support the F1, F2′ theory of speech perception.
Grammatical constraints and recognition performance
Authors: Price P. J. , Chow Y.-L. , Dunham M. O. , Kimball O. , Krasner M. , Kubala F. , Makhoul J. , Roucos S. , Schwartz R.
Published: October 2005

The integration of grammatical with acoustical knowledge sources in the BBN continuous speech recognition system, BYBLOS, and the resulting effects on performance are described. The system consists of feature extraction, acoustical scoring, and linguistic scoring. Feature extraction is based on vector quantized reel-warped cepstral coefficients. Acoustical scoring is derived from a hidden Markov model for each word, where word models are based on phonetic spellings so that models can be computed for words that have never been trained. The linguistic model is represented as a finite automaton derived automatically from a context-free specification of the task-domain syntax and semantics. It is shown how recognition performance varies with properties of the grammars. Word recognition accuracies of over 98% have been achieved in continuous speaker-dependent mode for 350-word tasks with grammars having maximum perplexity in the range of 20 to 60. [Work supported by DARPA and monitored by NAVELEX.]
Coherence-based enhancement of noisy speech
Authors: Atlas Lea E. , Clayton Alexandra J.
Published: October 2005

A standard coherence measure has been used to give an estimate of signal-to-noise ratio (certainty indicators) as a function of frequency. The two spectra which are used for this measure are the noisy speech spectrum and a model spectrum derived from pitch period estimates of the noisy speech. It is intended that the certainty indicators be used as either weights for matches in automatic recognition or as multiplicative weights for reconstruction of speech with improved intelligibility. Two cases of noisy speech have been studied: single words contaminated by bandpass-filtered white noise (S1) and sentences contaminated by unfiltered white noise (S2). For case S1 it has been found that the certainty indicators will pinpoint the noisy band for voiced speech and will, as expected, not reliably indicate the noisy band for unvoiced speech. For case S2, preliminary results indicate that the quality of the enhanced speech has dropped, yet the intelligibility is slightly improved. [Work supported by NSF and Boeing Computer Services.]
Adaptive filtering for speech enhancement
Authors: Clarkson P. M. , White P. R. , Mardell J. A.
Published: October 2005

Several authors have considered the use of adaptive noise cancellation for speech enhancement. These efforts have concentrated on the simple noisy gradient descent (LMS) algorithm and, in the absence of an external reference measurement, have formed a reference internally using a delayed version of the input. Limited improvements in SNR (for voiced speech enhancement) have resulted due to the inability of the filter to cope effectively with variations in power (of the speech) across frequency, discrete changes in the pitch period and because of the limited SNR of the reference. This study has approached the problem by replacing the noisy reference measurement by a synthetic reference which consists of a low-pass filtered series of discrete impulses at intervals corresponding to the pitch period of the input. This method has been compared with a modified version of the usual noise canceller (using an exact least-squares algorithm) on a sustained vowel segment. Higher SNR improvements for the synthetic reference have been measured. However, the method does require an estimate of the pitch period and appears quite sensitive to errors in this estimate.
A detailed examination of the path integral-based phase-space-marching algorithm for wide-angle, one-way wave propagation
Authors: Fishman Louis , Wales Stephen C.
Published: October 2005

The analytical approximations and numerical implementation of the path integral-based phase-space-marching algorithm are examined in detail. The approximate Weyl symbol constructions are evaluated with respect to the variations of the refractive index field on the wavelength scale, with attention focused on the particularly difficult case of very strong gradients. The local error, energy flux conservation, and effective stability of the numerical algorithm are discussed. Phase-space-filtering strategies are analyzed and illustrated with numerical computations. Detailed considerations involving the startup field, alternating false bottom, and range and depth step-size dependence are presented.
Benchmark problems used to test the implicit finite difference (IFD) model
Authors: Lee Ding , Botseas George , St. Mary Donald F.
Published: October 2005

The implicit finite difference (IFD) model was developed approximately 4 years ago to predict ocean acoustic wave propagation under variable environments. Its primary objective was to be “accurate” and “general purpose.” Since then, the model's capability has been improved. It has been widely used for research as well as for applications. During the test state for validity, a number of known solutions were used for reference comparisons. These test problems can be used as a severe test of a model's ability to handle variable environments accurately. This paper exhibits two test problems: One tests accuracy; the other demonstrates capability. In order to assess the computer code, how the mathematical model was developed, and how the method of finite differences was introduced along with an analysis of its accuracy, stability, and convergence are reviewed. Then, how the numerical solution was implemented into computer codes is discussed. Finally, the question is asked: What can this model do for you?
User evaluations of the acoustical characteristics of recently completed performing arts halls
Authors: Engle Donald L.
Published: October 2005

The evaluations of individuals who respond to, and live with, the acoustics of recently completed performance arts spaces have been surveyed. The views surveyed are those of performers, media critics, reporters, facility managers, and patrons. The ways in which such evaluations are used in selecting an acoustical consultant for a new or renovated facility are discussed.
Enhancement of protein synthesis by neuroblastoma cells exposed to ultrasound cavitation
Authors: Edmonds Peter D. , Ross Pepi , Yamawaki Ruth M.
Published: October 2005

Enhancement of the cavitational effect of iodine release from sodium iodide solution during repetitive 1-MHz tone burst excitation of the solution of a rotating test tube has been reported. [V. Ciaravino, H. G. Flynn, and M. W. Miller, Ultrasound Med. Biol. 7, 159–166 (1981)]. This enhancement was attributed to concurrent operation of two mechanisms: depletion of small nuclei from the cw mode size distribution generated during a tone burst, and survival from the previous tone burst of small nuclei lying in the same size range that is depleted in the cw mode. Twenty-four hours after exposing C1300 neuroblatoma cells (N2A) in rotating tubes to 1-MHz ultrasound tone bursts [1:1, durations from 6 to 600 ms; 3.4 W/cm2 spatial peak, burst average intensity, and 5 min total treatment duration (on + off periods)] at 37°C, enhancement of protein synthesis compared to control cells was observed. Protein synthesis was measured by uptake of H3-leucine. The similarity between results observed for cavitation-stimulated iodine release and cellular protein synthesis is highly suggestive of cavitation as the cause for this biological effect. [Work supported by PHS.]
Experimental results of an underwater magnetohydrodynamic transmitting acoustic transducer
Authors: Schreppler Stephen C. , Busch-Vishniac Ilene
Published: October 2005

The magnetohydrodynamic transducer operates on the familiar principle of the Lorentz force which results from interaction of electromagnetic fields in a conducting medium. The transducer investigated has the Lorentz force generated within an acoustic waveguide by a uniform magnetic field and a mutually orthogonal time harmonic current density interacting in a sodium chloride-water medium. The waveguide is 10 cm in length with a uniform 3.8 cm × 3.2 cm rectangular cross section, and is excited in the plane-wave mode. Acoustic power produced in the waveguide is radiated from apertures at either end of the waveguide into a surrounding free medium producing a dipole radiation pattern. Measurements of the transmitting sensitivity and radiation patterns are in good agreement with theory [J. Acoust. Soc. Am. Suppl. 1 78, S52 (1985)]. [Research supported by the Office of Naval Research.]