bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustical privacy for closed office design—Part II
Authors: Wyerman Barry R.
Published: October 2005

Sound attenuation was measured between two adjacent closed rooms sharing a common plenum area. The first part of this study [J. Acoust. Soc. Am. 64, SI, S149 (1978)] concentrated on sound transmission between rooms along a path through the ceiling and common plenum. A high STC wall limited the transmission of sound through the common partition. In this second part of the study, a partition with an STC of 36 was built in order to measure performance of each ceiling/partition assembly. Interzone attenuation measurements were conducted according to the PBS C.2 test method. These results were then compared with subjective responses to speech intelligibility for an elevated voice level in the presence of background masking sound. The results show a nearly constant signal to noise ratio that controls speech intelligibility. In addition, combinations of ceiling STC ratings, partition STC ratings, and masking sound levels are presented which provide signal to noise ratios that were subjectively judged to provide confidential speech privacy.
Frequency and temporal analysis in the hearing impaired: An overview
Authors: Wightman Frederic
Published: October 2005

During the past decade there has been a dramatic increase in research on the psychoacoustical correlates of hearing impairment. With the ultimate goal of understanding and perhaps alleviating the speech processing problems exhibited by many hearing-impaired persons, much of the recent research has focused on parameters of frequency and temporal analysis in impaired listeners. The results of the recent studies of frequency analysis, most of which include measures of the so-called psychophysical tuning curve, are relatively homogeneous. One tentative conclusion is that a loss of pure-tone sensitivity of 40 dB or more is almost always coupled with a loss of frequency resolving power. The results of the studies of temporal analysis are considerably more variable. Generally, it appears that a hearing loss is accompanied by degraded temporal resolution. However, some studies report that certain impaired listeners exhibit normal or better than normal temporal resolving power. Unfortunately, variability of this sort is typical of studies of hearing-impaired listeners, even though the listeners are carefully matched and well trained in the psychoacoustic paradigms.
Effects of masker level and signal delay on forward masking in normal and impaired listeners
Authors: Jesteadt Walt
Published: October 2005

Forward masking of a brief tonal probe by a long-duration tonal masker of the same frequency is determined primarily by masker level and signal delay. Forward masking was measured in listeners with normal hearing and in those with mild and moderate sensorineural losses as a function of both these variables. Tonal forward masking was also measured in normal listeners in the presence of continuous broadband noise, in an effort to simulate a sensorineural loss. The majority of the impaired listeners showed roughly normal decay of forward masking over time, but abnormal functions relating forward masking to masker level. Less forward masking occurs in impaired listeners than in those with normal hearing at all but the highest masker sound pressure levels. More forward masking occurs in impaired listeners than in normal listeners when maskers are equated in terms of sensation level at all but the lowest sensation levels. Use of background noise in tests of listeners with normal hearing does not provide a good simulation of sensorineural hearing loss. [Work supported by NIH.]
Implications of reduced frequency selectivity in cochlear impairment
Authors: Florentine Mary
Published: October 2005

This paper examines frequency selectivity in hearing-impaired listeners and discusses some of the implications of reduced frequency selectivity in these listeners. Different measures of frequency selectivity were examined in three diagnostic groups: otosclerotic, noise-induced, and degenerative. Frequency selectivity, whether measured by psychoacoustical tuning curves, narrow-band masking, two-tone masking, or loudness summation, was reduced only in the frequency region of a nonconductive impairment. The results across the four measures were significantly correlated and reduced frequency selectivity was positively correlated with the amount of impairment. The implications of reduced frequency selectivity are discussed briefly with regard to alterations in the loudness of complex sounds and impaired speech perception. The present masking measurements provide a basis for modifying Zwicker's [Acustica 8, 237–258 (1958)] model of loudness summation to apply to cochlear impairment. When the presence of recruitment, upward spread of masking, and enlarged critical bands are incorporated into the model, predictions of the model show reasonable agreement with loudness-summation data. Furthermore, cochlearly impaired listeners' difficulty in speech perception may be better understood by considering the increased spread of masking and the blurring of formants falling within the same enlarged critical band. [Work supported by NIH and NSF.]
Harmonic generation and response curves in a resonant system
Authors: Barmatz M. , Stoneburner J. , Jacobi N.
Published: October 2005

Harmonic generation in air was studied in a rectangular resonant chamber for sound pressure levels up to 160 dB. The nth harmonic pressure level, generated from the fundamental plane wave resonance (1.2 kHz) satisfied the expression, Pn = AnP1n, for n ⩽ 4 and fundamental sound pressure levels below 140 dB. The measurements were compared to a mathematical model [A. B. Coppens and J. V. Sanders, J. Acoust. Soc. Am. 58, 1133 (1975)]. The measured coefficients An were in good agreement with theoretical calculations. Above 140 dB, the fundamental response curves were skewed with peak values shifted to higher frequencies. Measured response curves were compared to a theoretical analysis of a modified Duffing equation [D. T. Blackstock, J. Acoust. Soc. Am. 34, 796 (1962)] with some agreement, indicating a hard spring behavior. The measurements will also be compared to recent first principle calculations of response curves. [Work supported by NASA.]
The pulsation amplitude of gas bubbles in a stationary sound field
Authors: Crum L. A. , Herring C. E. , Young D. A.
Published: October 2005

It has been known for some time that individual gas bubbles can be trapped near the pressure antinode of a stationary sound field provided they are driven below their resonance frequency. The acoustic force that balances the buoyant force is proportional to the pulsation amplitude of the bubble. This pulsation amplitude can be ascertained indirectly through measurements .of the acoustic pressure amplitude, the bubble radius, and the position of the bubble in the sound field. Further, the theoretical pulsation amplitude can be obtained by a solution of the well-known “Rayleigh-Plesset-Nolfingk-Neppiras-Poritsky equation” that has been used extensively in cavitation research. We present measurements of the pulsation amplitude of bubbles filled with various gases and in a variety of liquids at a frequency of 20 kHz. We also have obtained analytical solutions of the RPNNP equation by an expansion technique. Comparison of theory and experiment show good agreement for relatively small radii but substantial disagreement as the bubble radius approaches the resonance radius. It is thought that the source of the disagreement is the presence of surface waves on the bubble. [Work supported by the Office of Naval Research.]
Categorization of stop and nasal consonants by young infants
Authors: Hillenbrand James
Published: October 2005

A visually reinforced head-turn procedure was used to test six-month-old infants on phonetic-categorization tasks involving stop and nasal consonants. In one experiment, infants were reinforced for head turns when a change occurred from a series of background syllables containing nasal consonants (/m, n, n/) to comparison stimuli containing stop consonants (/b, d, g/). Each stimulus was produced by one male and one female talker. In another experiment, a separate group of infants was reinforced for head turns when a change occurred from syllables containing an initial /m/ to syllables containing an initial /n/. The stimuli were produced by male and female talkers in three vowel contexts: /a/, /i/, and /u/. The performance of infants in both of these “phonetic” experiments was compared to the performance of control groups run in “non-phonetic” experiments. In these experiments, stimuli were assigned to reinforced and unreinforced classes in such a way that the categories could not be organized by phonetic characteristics. Infants in both of the phonetic groups performed substantially better than infants in the corresponding nonphonetic groups. This finding suggests that infants in the phonetic groups recognized the phonetic similarity of the stimuli in the categories and used this information to organize their responses. [Work supported by NIH.]
Reducing speaker variation in Germanic: Improved results with PARAFAC
Authors: Disher Sandra Ferrari , Harshman Richard A. , Lundy Margaret E.
Published: October 2005

Previous applications of the PARAFAC factor analytic technique to the problem of vowel normalization [Disner, J. Acoust. Soc. Am. 67, 253 (1980)] have shown it to be well suited to cross-language comparisons, even though the actual reduction of the variance is moderate. In this paper we present the results of a more powerful PARAFAC-based technique, which still maintains the correct linguistic relationships in the data. Applied to data from six Germanic languages, extended PARAFAC normalization removes from 65% to more than 80% of the speaker-related variance, depending on the language; this compares favorably with the 21%–35% removed previously. Many of the factors extracted by PARAFAC are open to linguistic interpretation as dimensions of vowel quality. Factors corresponding to phonetic height, backness, and rounding have been identified across languages; certain other factors appear to reflect rhotacization and other, less readily interpretable dimensions. A comparison has been made of the ranges of these dimensions in phonetic space, their prominence within individual languages, and their recurrence in different languages.
Vowel normalization: Differences between vowels spoken by children, women, and men
Authors: Miller James D. , Engebretson A. Maynard , Vemula N. Rao
Published: October 2005

Using the data of Peterson and Barney [J. Acoust. Soc. Am. 24, 175–184, (1952)] we have sought transformations of the frequency scale (e.g., Mels) and rules of combination of values of the fundamental (F0) and the formants (F1, F2, and F3) (e.g., F2/F1, F3/F2) that will eliminate differences between talker groups (children, women, and men) while maintaining differences between vowel categories. The ratios of the between- to the within-vowel category variation as well as the minimum separations between vowel categories, scaled by the within-category variation, were calculated. Of the many frequency transformations and combination rules examined, the vector [log (F1/F̂), log (F2/F̂), log (F3/F̂)], where F̂ = (F1⋅F2⋅F3)1/3, provides the best clustering of the vowels and nearly eliminates differences between talker groups. This suggests that vowels are characterized by their spectral shapes when plotted on log axes. Thus the usual range of differences between children, women, and men in the absolute location of the spectrum along the log-frequency axis appears unimportant. [Supported by Grant NS 03856 from NINCDS.]
Phonotactic basis for word frequency effects: Implications for lexical distance metrics
Authors: Eukel Brian
Published: October 2005

Word frequency influences both the production and perception of speech. Speakers increase stress for infrequent words, and poor listening conditions cause listeners to mistake rare words for common ones, but not vice versa. People can also directly estimate relative word frequencies to within one order of magnitude of their objective values. To determine if word frequency effects were determined at least in part by phonotactics (versus by semantics), subjects were asked to estimate word frequencies for a list of words containing both real and nonsense words. Subjects duplicated previous results in their ability to judge the frequency of real words, and showed significant agreement in their judgements of “frequencies” for nonsense words. Subjects' judgments for the frequency of nonsense words showed significant correlation with Greenberg and Jenkins' measure for distance from English, implying that word frequencies are judged by estimating the density of similar sounding words in the lexicon. These results suggest additions to lexical distance metrics that would improve performance of speech recognition systems: small vocabulary systems could tabulate word frequency during system usage and bias recognition towards more frequently used words, while large vocabulary systems could use lexical density to modulate calculated distances between candidate words and the input utterance.
The acoustic origin of the smile
Authors: Ohala John J.
Published: October 2005

In many species, appeasement or submissive vocalizations have a high fundamental frequency in order that the sender may sound like an infant and thus elicit a parental helping response from its would-be antagonist [Morton, Am. Nat. 111, (1977)]. High vocal tract resonances may also enhance the infantile character of the vocalization by seeming to originate from a shorter vocal tract. Higher resonances can be achieved by a trumpet-like flaring of the tract and/or by retracting the corners of the mouth. This latter gesture, I hypothesize, is the origin of the smile. Ritualization of the visual component of this acoustically motivated gesture accounts for the smile often being performed soundlessly by man and higher primates. The upshifting of the resonances due to mouth corner retraction and/or flaring was simulated using pulsed plasticine models of vocal tracts. Significantly, the ethological literature also documents a widely found cross-specific aggressive display that involves constriction and protrusion of the lips, which by lowering the resonances of the vocalization would enhance the impression that the sender was very large.
Comparison of conventional and reduced-redundancy beamformers
Authors: Parkins Bowen E.
Published: October 2005

In reduced-redundancy beamforming, certain of the elements which give rise to redundancy in the spacings of uniform arrays are removed, and the contribution to beam power for these spacings is made by signal-processing means. The aim in doing this is to reduce the number of array elements while maintaining the angular resolution and beam power of a fully populated array with the same baseline. In this paper it is shown that such performance can be realized in practice using this technique but at a cost of degraded side-lobe and detection performances. Also, the dependence of the beam performance on the homogeneity of the second-order statistics of the received pressure is demonstrated. In particular, the mainbeam properties are shown to be fully equivalent to those of a conventional processor when the pressure is homogeneous over the array aperture. When this is not the case, differences in beam patterns arise; the nature of these depends upon both the pattern of the inhomogeneity and the way in which the processing is done.
Multidimensional filters for sonar target detection
Authors: Aaron Arnold M.
Published: October 2005

Sonar systems have been conventionally optimized for the detection of “point” targets, yet many targets of interest are continuously distributed. The detection and localization of such complex targets has typically been accomplished by the use of Artificial Intelligence techniques operating on an input of thresholded “point” targets. We recognize that sonar “observables” for a distributed target consist of a tensor whose components of target range, doppler, and angle are vectors rather than scalars. Questions exist as to the dimensionality of any single but distributed target as well as the discriminations of targets from other large features such as reverberation. The approach taken in the current work is to utilize multiple filters, distributed in dimensionality, operating in a parallel manner on bus distributed sonar data. We believe that multidimensional filters operating on the vectored time series output from conventional sonar systems will lead to improvements in the detection of distributed targets.
Very high data rate television using the parametric acoustic source
Authors: Konrad W. L. , Clay W. L.
Published: October 2005

Television pictures with a video bandwidth of 35 kHz were transmitted acoustically over a 4-km water path in Seneca Lake, New York State. The parametric source used a 25-cm-diam projector having a mean primary frequency of 245 kHz. A combination of a scan converter and a speed changing tape recorder resulted in a 265-line picture with a frame rate of one per second. The narrow 2° beam-width minimizes multipath distortion and makes high speed acoustic: transmission feasible.
Effect of alcohol on acoustic reflex relaxation
Authors: Robinette Martin S. , Alper Randi R. , Brey Robert H.
Published: October 2005

The Reflex Relaxation Index (RRI) was introduced by Norris et al. [Arch. Otolaryngol. 99, 194–97 (1974)] as an objective test for sensorineural hearing loss. The test consists of measuring the acoustic reflex response to pulsed pure tone stimuli. Sensorineural loss subjects show a different response pattern due in part to an increased reflex relaxation latency. Brey and Robinette [J. Acoust. Soc. Am. Suppl. 1 63, S53 (1978)] noted that post stimullus reflex latencies were increased for normal hearing subjects following the ingestion of alcohol. In the present study eleven normal hearing subjects were given the RRI test under two alcohol conditions: blood alcohol levels of 0.00 and 0.10%. Results showed six of the eleven subjects changed from a diagnosis criteria of normal cochlear function to that of sensorineural loss following alcohol consumption. Data suggests a simple positive or negative interpretation of the RRI test is not always appropriate.
A comparison of brainstem evoked response (BSER) and psychophysical estimates of auditory frequency selectivity
Authors: Brown D. D. , Kidd G.
Published: October 2005

The effect of pure-tone masking on the auditory brainstem response has received relatively little attention. This study investigated the effects of pure-tone masking on the BSER and compared this to behavioral data acquired from the same subjects using a similar forward masking paradigm. A 35-ms masker (10-15- 10 ms for rise-steady state decay) at several frequencies was used to alter the BSER to a 4-kHz, 5-ms (2-1-2 ms) probe. There was a 5-ms silent interval between masker offset and probe onset. At masker levels lower than those which eliminated the BSER, the masker caused both latency increases and amplitude reductions. The psychophysical procedure was a 21FC detection task with a fixed-level probe and variable-level masker. Surprisingly, given the extremely brief (in psychophysical terms) probe, the effect of the maskers was frequency dependent, yielding reasonably sharp “psychophysical tuning curves.” By choosing an arbitrary criterion for alteration of the BSER, a similar frequency dependence of the masker effect was observed. [Work supported by a David Ross Fellowship from Purdue University and grants from N.I.H.]
Acoustic Microscopy at Optical Wavelengths
Authors: Heiserman Joseph E.
Published: October 2005

Recent developments have allowed the state of the art in acoustic microscopy to progress to the point where acoustic wavelengths equal to and even shorter than visible light wavelengths are now employed. Examination of samples from biology, materials science and integrated circuit technology has revealed several areas of application. Through the use of cryogenic liquids as an acoustic coupling medium very high resolution has been attained and still better resolution, far surpassing the optical microscope, is expected.
Acoustics of thunder III: Mapping the 3-dimensional shape of lightning into the sound of thunder (with audible demonstration)
Authors: Roy Dipankar , Ribner H. S.
Published: October 2005

In 1972 (Buffalo) a p(t) plot of “thunder” was derived from a photograph of lightning and in 1975 (Austin) this was made briefly audible. The present much advanced modeling of the lightning→ thunder process has evolved from a long-term effort. Considerations: the tortuosity of the initiating lightning stroke is responsible for the long duration rumble and roll. Forbidding mathematical difficulty has limited rigorous nonlinear analysis to a rectilinear channel: this yields but a single short thunderclap. To deal with tortuosity an approximate theory linearly sums N waves evolving from each point of the stroke. Procedurally, a computer simulates tortuous three-dimensional lightning channels via a Monte Carlo technique governed by appropriate statistics; the extensive thunder algorithm is subsequently applied. The computer output is fed through a D/A converter-amplifier-loudspeaker system to produce audible synthetic thunder. We demonstrate a 50 s “thunderstorm”: the degree of similarity with real thunder can be assessed by the audience. As a further comparison, for a straight lightning channel the approximate and rigorous theories predict very similar short thunderclaps.
Electrostatic interactions and the piezoelectric equations
Authors: Tiersten H. F.
Published: October 2005

In piezoelectricity, the stress equations of motion are coupled to the charge equation of electrostatics by means of the linear piezoelectric constitutive equations which contain the piezoelectric constants that couple the small strain to the electric field. In the case of the more general nonlinear interaction of the electric field with a deformable insulator, the Maxwell electrostatic stress tensor must be included in the description. Furthermore, in the nonlinear case, a rotationally invariant combination of the electric field and the deformation occurs in the constitutive equations in place of the electric field for the same reason that the finite train occurs. The linear electroelastic equations for small dynamic fields, superposed on a static bias obtained from the nonlinear system, are more general than the linear piezoelectric equations in that the linear constitutive equations depend on the small local mechanical rotation, as well as the small strain. Nevertheless, when the biasing stress and electric field vanish, even though a biasing strain and polarization are present, the equations reduce to those of linear piezoelectricity. Consequently, the linear equations for the polarized ferroelectric ceramic, which operates essentially by means of biased electrostriction, are identical with those of linear piezoelectricity for the symmetry of the polarized state. When the biasing electric field is retained in the linear electroelastic equations, they are applicable in the description of the self-biased electret microphone. The influence of any bias on the frequency response of a piezoelectric resonator may readily be obtained from the linear equations for small fields superposed on a bias with the aid of an existing perturbation equation. Some examples are given.
TDS and beyond
Authors: Thomsen Carsten
Published: October 2005

Time delay spectrometry can be implemented in a number of different ways, both analog and digital, or a combination of the two. This paper describes the different techniques and places special emphasis on the oft neglected time domain parameters that can be extracted by TDS. Of special interest are the so-called energy time curve, the impulse response, time domain phase, and its derivative, instantaneous frequency. By invoking the Hilbert transform to derive these measurements, a complete symmetry between time and frequency domain representations is achieved. Based on these symmetry considerations, new, but easily implemented measurements are suggested for future studies.
Cochlear microphonic (CM) interference functions
Authors: Cheatham Mary Ann , Dallos Peter
Published: October 2005

Two-tone effects are explored for the cochlear microphonic (CM) in the guinea pig. Recordings are made from several turns using differential electrodes or single pipettes placed in scala media. In these experiments, the CM is elicited by a continuous tone, the probe. while a second continuous tone of variable frequency and level, the interference tone, is used to reduce CM magnitude. Frequency-intensity pairs for interference tones which yield a constant decrease in probe response generate the CM interference function. Results reveal that the CM is most effectively reduced by interference frequencies which are greater than the “best frequency” of the electrode site. However, low-frequency interference tones can also decrease CM magnitude under appropriate conditions, although in a nonfrequency-specific manner. Thus the interference functions are asymmetric and have a single minimum. Similarities between our results and two-tone suppression in the auditory nerve will be highlighted. [Work supported by NINCDS.]
Effects of vanadate on cochlear potentials (guinea pig)
Authors: Marcus D. C. , DeMott J. , Thalmann R.
Published: October 2005

In numerous tissues, vanadate is a potent inhibitor of Na/K-ATPase. Inhibition of Na/K-ATPase is thought to account for its diuretic action. Because of the high activity of Na/K-ATPase in the stria vascularis (SV) and the sensitivity of the endocochlear potential (EP) to ouabain, we investigated the effect of vanadate upon strial function. Because of pronounced systemic effects, the agent was perfused perilymphatically (0.1 and 1 mM) while the EP and the cochlear microphonics (CM) were recorded. Perfusion through scala vestibuli produced no major short term effects; in contrast, perfusion of scala tympani with 0.1 mM vanadate resulted in a rapid, pronounced increase of the EP (averaging 15 mV) which lasted several minutes. Subsequently, the EP dropped gradually to an asymptotic value of about +40 mV. The CM started to decline concurrently with the rise of the EP, with the decline more pronounced at 1 mM. These data suggest that the action of vanadate is initially exerted upon the organ of Corti rather than the SV. Although strial Na/K-ATPase is strongly inhibited by vanadate in vitro, protective mechanisms apparently exist under in vivo conditions. [Supported by NSF and NIH.]
The effects of acoustic stimulation on glucose utilization in the inner ear
Authors: Ryan Allen F. , Goodwin Paul , Woolf Nigel K. , Sharp Frank R.
Published: October 2005

Glucose uptake into tissue can be mapped by the incorporation of 14C-2-deoxyglucose (2-DG). However, this technique as employed in previous investigations does not lend itself to use in the cochlea. We have developed an alternative technique which permits the visualization of 2-DG uptake in the tissues of the inner ear. 2-DG (16 μCi/100 g in 0.1 ml) was injected intracardially into gerbils. Animals were exposed to wide band noise at intensities of 25, 45, 65, 85. or 105 dB SPL for one hour in a double-walled sound attenuated chamber. Control subjects received no exposure. Gerbils were then sacrificed by decapitation, and the cochleas dissected whole and frozen in Freon 12 cooled to −160°C. Inner ears were then freeze-dried. embedded in Epon or Spurr resin utilizing only organic solvents. and cut in mid-modiolar section. Half cochleas were exposed on LKB Ultrofilm for 10 days. Control inner ears showed maximal uptake of 2-DG in stria vascularis. Our initial data indicate that incorporation of 2-DG increased in the spiral ganglion and VIIIth nerve during exposure to noise, especially at 85 and 105 dB SPL. [Work supported by NIH/NINCDS grants NS00176 and NS14945.]
Nonlinear distortion of fourth sound in superfluid 3He-B
Authors: Garrett Steven
Published: October 2005

The relative density of the superfluid component of 3He is expected to be significantly depressed by flow. For this reason the distortion of a finite amplitude fourth sound wave exhibits an unusual amplitude dependence. For waves of sufficiently large initial amplitude, a fully developed shock wave will contain two discontinuities per wavelength. Calculations which determine the threshold amplitude are presented and comparison with thermodynamic data suggest that waves of sufficient amplitude should be experimentally accesible. [Work supported in part by the Hunt Postdoctoral Fellowship of the Acoustical Society of America and the Miller Institute for Basic Research in Science.]
Nonlinear acoustic force on spherical samples
Authors: Leung E. W. , Jacobi N. , Wang T. G.
Published: October 2005

The force exerted by standing acoustic waves on spherical samples is investigated experimentally in a rectangular resonance chamber. The experiment was performed at acoustic intensities up to 84 dB above one tenth of N/m2. With the amplitude of the second harmonic, p2, suppressed (experimentally by adding a p2 component at opposite phase), the measured force is in good agreement with King's theoretical calculation [Proc. R. Soc. London A 147, 212 (1934)]. With no harmonic suppression, the measured force follows Westervelt's calculation [J. Acoust. Soc. Am. 22, 319 (1950)] at low intensities, with gradual deviations at higher intensities. A theoretical model was developed for the effect of higher harmonics on the acoustic radiation pressure and on the acoustic force, which can be compared qualitatively with the present measurements. The dependence on the sample radius and the chosen gaseous medium will be discussed. [Work supported by NASA under contract number NAS 7-100.]
Acoustic streaming near a sphere in a compressible fluid
Authors: Bundy M. , Rooney J. A.
Published: October 2005

Theory is presented for acoustic streaming near a sphere in a compressible medium. Starting with the Navier-Stokes equation, the method of successive approximations was used to obtain solutions for the fluid velocities for appropriate boundary conditions. For conditions such that the fluid is relatively incompressible or when the sphere radius is much less than (1/1000) the wavelength of sound in the medium, the acoustic streaming patterns are similar to those previously described. For situations where the effects of fluid compressibility are important the streaming pattern is drastically changed. The symmetry changes from the four-quadrant type of the incompressible-fluid case to one which is symmetric only with respect to the axis of oscillatory motion. This symmetry is such that for a traveling plane-wave field the streaming velocities near the sphere axe greater in the region nearer the sound source. For the case in which the sphere radius is approximately the size of the boundary-layer thickness, the inner circulation of the streaming pattern moves away from the sphere and symmetry is of the four quadrant type.
On the nonlinear generation of harmonics in sound radiation from a vibrating planar boundary
Authors: Ginsberg Jerry H.
Published: October 2005

This analysis employs Fourier transform theory and perturbation methods to investigate the finite-amplitude acoustic waves that are induced by harmonic vibration of a region in an infinite planar boundary. Only situations leading to two-dimensional waves in inviscid fluids are considered. A perturbation series is employed to obtain differential equations governing the first-order (linear) and second-order (first nonlinear correction) terms in the velocity potential. A Fourier transform leads to a description of the linear potential in terms of propagating and evanescent nonuniform planar waves occurring in a continuous spectrum of transverse wavenumbers. The linear solution is used to evaluate the source terms for the second-order potential. The portion of the latter which exhibits cumulative growth of higher harmonics is evaluated by a method based on the principle of stationary phase. The results indicate that harmonic generation at a specific transverse wavenumber is primarily independent of the response associated with other wavenumbers. [Research supported by NSF, grant ENG 7824602.]
Nonlinear eigenmodes and acoustic solitons
Authors: Korpel Adrianus , Banerjee Partha P.
Published: October 2005

In a recent investigation [A. Korpel, J. Acoust. Soc. Am. 67, 1954 (1980)] spectral evolution equations were derived for a nonlinear dispersive medium. For the special case of two harmonics, two eigenmodes were derived of which one was shown to be parametric in nature. In this paper we present results of a stability analysis of these modes. It is shown that their limit-cycle behavior is in agreement with earlier results from nonlinear optics [J. A. Armstrong, N. Bloembergen, J. Ducuing, and P.S. Pershan, Phy. Rev. 127, 1910 (1962)]. We will also present some results for the case of more than two harmonics, and will discuss the relation of these modes to cnoidal waves and acoustic solitons. [Work supported by NSF.]
Atmospheric waves from large meteors
Authors: ReVelle D. O. , Wetherill G. W.
Published: October 2005

The body of airwave data taken by the U.S. Government for the purpose of atmospheric monitoring of distant nuclear explosions, contains fortuitously waves of natural origin as well. We have recently received a portion of this original data base which contains only those signals which are presumably of meteoric origin; other natural signals such as from aurora, volcanic eruptions, meteorological phenomena, etc. having been previously removed from the sample. The ten meteoroid related events have amplitudes of about 0.5 to 10 dynes/cm2 and periods at maximum signal amplitude of about 3 to 45 s at horizontal ranges of about 800 to 14 000 km from the source. Using appropriate signal characteristics with models for the source and for propagation of these waves, source energies can be inferred. For these events energy estimates range from about 0.1 kT to as much as 550 kT (TNT equivalent) assuming that a low altitude point source explosion model is applicable. This detailed data set, having been recorded at several widely spaced arrays around the globe, could be used for a new attempt at modeling the propagation of such waves perhaps using methods suggested by Pierce and Kinney. [AFGL-TR-76-0056, Final Report, 13 March 1976.]
An anechoic chamber and point source design for audiological measurement
Authors: Gilman Samuel
Published: October 2005

A point source in a 6-ft cubed anechoic space was designed to provide predictable audio sound fields at 1 m without near-field effects. The chamber was acoustically isolated to permit measurement down to 25 dB SPL in an 812 × 9 × 11foot o.d. enclosure. A control microphone 20 cm from the source maintained a constant SPL at 1 m over the entire frequency range. The presence of a full size human manikin did not affect the sound field at the control microphone. SPL followed inverse square law (± 1 dB) from 10 cm to 1 m from the source over a 200 Hz to l0 kHz frequency range. Eight loudspeakers, mounted behind the upper edge wedges could develop 70 dB SPL quasi-diffuse noise at the working location.
Audibility of phase changes in vowel sounds and complex tones
Authors: Stern Richard M. , Waibel Alexander H.
Published: October 2005

This research was motivated by recent observations of a relatively strong perceptual salience of phase relations among harmonics in the vowel sound /ae/ [Carlson et al., J. Acoust. Soc. Am. 65, S6(1979)]. Phase had contributed relatively weakly to timbre in classical psychoacoustical studies using complex tones. We investigated the audibility of phase changes in vowels and complex tones using a forced-choice paradigm in which subjects discriminated between sounds presented with all harmonics in phase and a similar stimulus with a phase shift for the even harmonics that was varied from 0 to 90 degrees. “Phase discrimination thresholds” were obtained by determining the phase shift needed to produce criterion discrimination performance. Our preliminary findings indicate no major differences between the audibility of phase changes for vowel sounds and complex tones. Its joint dependence on fundamental frequency and number of harmonics is consistent with results in the literature. These findings are also compared to the audibility in vowel sounds of phase shifts as produced by the vocal tract.
Pulse response of propagation channels using the Parabolic equation method
Authors: Nghiem-Phu Lan , Tappert Frederick D. , DeFerrari Harry A.
Published: October 2005

The Parabolic equation method with split-step Fourier algorithm models cw transmission in range-dependent channels. For some applications, it is desirable to predict the impulse response of the channel. The Parabolic equation code has been applied to each cw component of the Fourier-decomposed transmitted signal and the pulse response resynthesized at the receiver. This method was used to study the transmission in the Arctic ocean [Kutschale and Tappert, J. Acoust. Soc. Am. Suppl. 1 62, S18 (1977)]. We model range-dependent bottoms and profiles for shallow water sound transmission in the Florida Straits. Pulse responses are given for surface ducts and also for SOFAR propagations. Results are compared with the range-dependent ray theory. Pulse responses near caustics are examined. [Work supported by ONR.]
Propagation over a seamount
Authors: Jensen F. B. , Kuperman W. A. , Medwin H.
Published: October 2005

Experiments at sea by G. R. Ebbeson, J. M. Thorleifson, and R. G. Turner [J. Acoust. Soc. Am. 64, S76 (1978)] and in a laboratory by H. Medwin and R. P. Spaulding, Jr. [J. Acoust. Soc. Am. 66, S76 (1979), and in W. A. Kuperman, F. B. Jensen, Eds., Bottom-Interacting Ocean Acoustics (Plenum, New York, 1980)] have recently studied sound propagation over a seamount. The results of these experiments are compared with theoretical calculations using the parabolic equation. These experiments include the effects of reflection, refraction, scattering and diffraction. To a certain extent; the parabolic equation includes all of these effects and it is possible to identify some of these phenomena. Results are presented illustrating the (frequency-dependent) relative importance of these effects together with the agreement in total sound-field level between theory and experiment. [H.M. supported by the Office of Naval Research.]
Sensitivity of the level weighted population (LWP) noise impact scale to uncertainty in source noise levels and distances to receiving property
Authors: Lane Sam R.
Published: October 2005

Integral expressions were formulated and solved for the LWP attributable to point or line sources in terms of source noise level and impacted-area dimensions. Expressions were then derived for relative error in LWP due to uncertainty limits on source noise level and source-to-receiver distance. From these results, expected errors in LWP for variable standard deviations in source noise levels or distances were calculated. In the case of multiple sources, the average expected error in LWP for both equally distributed and normally distributed source levels, and source-to-receiver distances were estimated. This paper summarizes the study results.
Temporal sampling requirements in the vicinity of army bases
Authors: Schomer Paul D.
Published: October 2005

Assessing the statistical reliability of monitored data is a complex problem, particularly for highly variable sources over long distances such as in the vicinity of Army bases. To begin to quantify these requirements, data from four airports (Los Angeles, Boston, Dallas, and National) were analyzed. Temporal requirements and time series models were developed. Operational data from a typical base were used to form an “operations” model. Using primarily the L.A. data as a weather model, on overall Army model was formed as the “product” of the weather and operations models. Results from the various models indicate large sampling requirements (50–150 consecutive days) in order to achieve results within +2 to −3 dB of the true yearly DNL value with a 95% confidence.
Performance of an L
dn estimator
Authors: Seaman John W. , Putnicki George J.
Published: October 2005

Period Leq and 24-h Ldns were obtained at 10-min intervals for seven 24-h monitoring periods at each of several single-family residential sites using A.N.S.I. Type I sound-level meters. For every 10-min Leq, a corresponding 30- and 60-min. Leq was computed having the same starting time. To simulate a sampling strategy employed in community noise assessment projects (Wyle Research Report WR-77-17), every possible combination of nighttime and day-time Leqs was formed for each type of period Leq. The resulting ordered pairs formed the domain for a commonly used Ldn estimator (Wyle Research Report WR-77-17). Using the measured Ldn, the error for each estimate was computed. Various statistical measures of the errors were used to examine the relative effect of each level of Leq on the accuracy and variability of the estimates. To investigate possible patterns of time regions yielding minimal error, contour plots representing the overall average error as a function of day and night time were computed for each level of Leq.
Synthesized propfan interior noise
Authors: Dempsey Thomas K. , Shepherd Kevin P. , Stephens David G.
Published: October 2005

Recent fuel-conservation measures have led to increased interest in propeller-driven aircraft for commuter as well as long-haul applications. The increased fuel efficiency of these vehicles could be offset, however, if passenger acceptance necessitates increased aircraft weight for purposes of noise reduction. Thus, a laboratory investigation was conducted to describe passenger acceptance criteria for the interior noise environment of these vehicles, and as a corollary, to assess the validity of various noise descriptors or metrics for quantifying the interior noise environment. The investigation was conducted in the passenger ride-quality simulator located at the NASA-Langley Research Center. The tests involved a total of 96 subjects which evaluated synthesized propeller noises using a nine-point discomfort category scale. The sounds consisted of a turbulent boundary-layer noise with a factorial combination of blade passage frequencies (50, 80, 100, 125, and 200 Hz), harmonic rolloffs (0 and 10 dB harmonic), tone/noise ratios (0, 10, and 20 dB), and noise levels (85, 90, 95, and 100 dB). The results indicate that noise-level and blade-passage frequency are the primary noise characteristics that determine passenger reaction. Although A-weighted noise level was determined to be the most accurate predictor, additions of up to 8 dB (Corrections) were required in some cases to fully account for passenger reactions.
Phase- and group-velocities of acoustics waves around a sphere simulating the human head
Authors: Gaunaurd G. C. , Kuhn George F.
Published: October 2005

Phase-derived interaural time differences (ITD) have been determined previously [G. F. Kuhn, J. Acoust. Soc. Am. 62, 157–167 (1977)] for steady-state sinusoids. It has been speculated (e.g.. J. Blauert or E. A. G. Shaw, Sound Localization Symposium, University of Guelph, Canada, 1979) that localization of signals, more complex than pure tones, is based on the interaural group-delay rather than on the phase-derived ITD. Therefore, phase- and group-velocities have been calculated for the first five acoustic modes “creeping” around the perimeter of spheres, assumed rigid, between 0.4 ⩽ ka ⩽ 25.0 , where “K” is the wavenumber and “a” is the radius of the sphere. The group velocities for all modes are zero at ka = 0.0. The group velocities for the first, second, and third mode are approximately 0.92, 0.72, and 0.63 of the ambient speed of sound, respectively, at ka = 2.0. Further results comparing interaural group-delayed time differences to phase-derived ITDs will be presented.
Speech perception through various signal processings
Authors: Nábĕlek Igor , Wood W. Scott , Koike Kazurani J. M.
Published: October 2005

Modified rhyme test (MRT) and the City University of New York nonsense syllables test (CUNY) were recorded through various speech processings: (1) amplitude compression for a 10:1 compression ratio (CR) with attack and release times 10 and 90 ms, respectively; (2) amplitude compression plus two types of peak clippings (CLIP); (3) amplitude compression plus high-frequency emphasis (HFE) with different attack and release times; and (4) three-channel multiband compression (MBC) in which the CR in each channel was adjusted on the basis of the subject's dynamic range. The compression threshold was set 25 dB below the average maximum RMS level of the vowels of test items in the MRT or CUNY. The processed signal was amplified with individually adjusted frequency responses and delivered to the listeners via a circumaural earphone. The presentation of speech was always at the comfortable level for each individual listener. All the testings were done in quiet. The MRT mean scores in percent correct did not differ among test conditions. The CUNY mean scores in percent correct were 8% higher on the average for compression or compression plus CLIP, 8% lower on the average for compression plus HFE, and about the same for MBC in comparison to the reference score for no compression (CR = 1). The results of the statistical analysis will be presented. [Work supported by NIH NS 12946.]
Investigating a tactile speechreading aid: Transmission of prosodic information in connected discourse and sentences
Authors: Grant Ken W. , Kuhl Patricia K. , Ardell LeeAnn H. , Sparks David W. , Carey Bryce
Published: October 2005

Variations in the voice-fundamental frequency were extracted from naturally produced samples of connected discourse and sentence materials and were transmitted to an electrocutaneous, forearm display that consisted of 10 electrodes in a linear array. Changes in fundamental frequency were encoded as changes in stimulus location. The rate of speechreading with and without the aid was examined for both kinds of stimulus materials with one profoundly hearing-impaired listener and one normal listener who was artificially deafened. Listeners were tested in a connected-discourse tracking procedure for a minimum of 20 hr. Results demonstrated that subjects' tracking rates with the aid were substantially higher than without the aid. Results from the sentence-discrimination tests revealed that aspects of sentence intonation, stress, and rhythm, which are not easily speechread, are readily available with the aid. [Partially supported by NIH.]
Effects of spectral overlap on the discrimination of the temporal order of tone pairs
Authors: Kelly W. J. , Watson C. S.
Published: October 2005

Observers were asked to discriminate the temporal order of two tones with frequencies 550 Hz and (550 + ΔF) Hz. The interval between the tones was 5 ms. Tones were of equal duration, were linearly gated with 2.5 ms rise/decay, and were presented at 75 dB SPL. The psychophysical method was a modified two-alternative-forced-choice procedure in which the stimulus sequence designated as the “signal” was presented before each pair of observation intervals. Tone durations were varied according to a transformed-up-down adaptive rule (Levitt, 1971) which converged on the durations required for 71% correct responses. Testing was done primarily for frequency separations of ΔF = 5, 10, 20, 40, and 80 Hz. Results indicate that for the frequency separations used, observers require tone durations which result in a constant amount of spectral overlap. For example, frequency differences of 10 and 40 Hz result in tone durations of 20 and 8 ms, respectively, to maintain 71% correct responses. Introduction of 100-ms leading and trailing tones at the geometric mean of the target-tone frequencies yields marked increases in tone-duration thresholds, with the degrading effect of the trailer alone nearly as large as that of the leader and trailer combination. [Work supported by NIH.]