bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimental and computer study of the spatial distributions of p2 in a reverberant enclosure at low frequencies
Authors: Ochs J. B. , Tichy J.
Published: October 2005

In a diffuse sound field the spatial distributions of p2 are exponential. Because in an enclosure the diffusion of the sound field is not perfect, it is necessary for some applications, such as the sound power measurements, to know how much the statistical distributions deviate from exponential, particularly at frequencies lower than the critical frequency fc = 2000 (T/V)1/2. Therefore, both computer and experimental studies were conducted from below the first mode in an enclosure up to and above the critical frequency in 1-Hz frequency increments with p2 calculated and measured in 120 spatial positions. Both probability density functions and cumulative distribution functions as well as the deviation from the exponential distributions were obtained. Computer-generated second order statistics have been investigated to determine the effect of a finite number of points used to generate the distributions. Based on the frequency dependence of the deviation of the actual distributions from the exponential distributions, it can be concluded that the reverberation room is usable from a lower frequency than fc.
Study of the sound transmission class system for rating building partitions: Another view
Authors: Sepmeyer Ludwig W.
Published: October 2005

In an earlier paper titled “Subjective Study of the Sound Transmission Class System for Rating Building Partitions,” D. M. Clark concluded that his results showed that the ASTM E413 method for determining a rating from measured transmission-loss data yields conservative values even when there are large dips in the TL characteristic. Clark's experimental procedure had the subjects match the annoyance produced by a degraded STC shaped sound channel by increasing the level transmitted by a pure STC contour shaped channel. By this method, instead of having a fixed reference annoyance, the reference first established in the pure STC channel is increased in proportion to frequency, bandwidth, and depth of the degradation introduced into the so-called TL channel. If instead the reference annoyance had been kept fixed and the degraded TL channel had been readjusted to match the chosen criterion value of annoyance, quite different results would have been obtained. By using speech articulation index computations, it is shown that instead of being conservative, the rating procedure can overrate TL characteristics with high-frequency octave band dips as much as five points. Instead of abandoning the 8-dB limitation completely, it is proposed that a limitation of 16 dB for the sum of any three adjacent bands be substituted.
The successful auditorium: Some acoustics and a lot of psychology
Authors: Dickinson Philip
Published: October 2005

Remedial measures to a large, well-known concert hall produced acoustics that, the acoustical consultants believe, are as good as any in the world today. Performers, concert goers, and critics were unanimous in their expressions of delight during the first concert season. There were high hopes of it becoming one of the world's great auditoria. But, all is not well and opinions are changing even though the acoustic characteristics remain unchanged. The paper discusses the other factors involved in producing a successful auditorium and suggests reasons for the demise of this hall and for the popularity of some others in which the acoustics, to be polite, can only be described as “interesting.”
The tempered Fourier transform
Authors: Teaney Dale T. , Moruzzi Victor L. , Mintzer Frederick C.
Published: October 2005

3 2  = 2 7.01955/12  ≅ 2 7/12 . The set of harmonics (l = 1, 2, 3), 1/Kl = (29, 14, 13) ≅ (25/12, 27/12, 2), when scaled by 2am/12, m = 1, 2, 3, 4, constitutes a logarithmically uniform set, flm, of 12 frequency classes per octave (8 va). The tempered Fourier transform samples a record x(t) into four independent parallel sequences xm(i) at sampling rates 2m/4. In each 8 va, n, of each sequence, m, three Fourier coefficients, Xlmn(j) = Σ xmn(j − i)W(i/NKl)exp − j(2πi/Kl) are computed, where W(i/NKl) is a window N cycles long, and xmn(j) = Σ hkxmn+1(2j − k) is the data sequence in the nth 8 va after it has been low-pass filtered and decimated from the (n + 1) 8 va above by a half-band filter with impulse response h. With a suitable value of N, the array Xlmn is statistically and dynamically equivalent to a 112–8 va spectral analysis of x. Examples and variants of the method will be discussed.
Vocal jitter in singers voice
Authors: Murray T.
Published: October 2005

Cycle-to-cycle variations in the period of the vocal fold waveform, known as jitter or frequency perturbation, are a natural quasiperiodic property of the glottal sound source. Excessive jitter in the voice signal represents an undesirable vocal parameter which the singer strives to minimize. This study examined the degree of frequency perturbation in female singers' voices during the production of sung and spoken vowels. Four female singers produced the vowel /a/ in one spoken and four sung conditions. Magnitude perturbation measures were obtained for a steady state portion of each sample. The samples were also submitted to a panel of listeners who were asked to rate the degree of roughness in each vowel. The perceptual results from those judges who performed reliably were compared to the measures of vocal jitter. The results indicate that singers' spoken samples contain less jitter than their sung vowels. The perceptual ratings indicated that listeners were not able to judge the group in relation to their perturbation measures.
A physiological interpretation of vocal registers
Authors: Titze I. R.
Published: October 2005

Vocal registers have been described acoustically and perceptually, but little is yet known about register control at the muscular level. An attempt is made here to describe vocal registers as stable or transitional regions in a four-dimensional space consisting of cricothyroid, thyroarytenoid, interarytenoid, and pulmonary stress. The chest register is shown to be the central and most stable region where conditions for oscillation are optimal. Falsetto and glottal stop are other physiologically stable and robust regions, but conditions for oscillation are less favorable. Vocal fry and creaky phonation tend to manifest themselves as transitional states between stop, chest, and falsetto. Glottographic, electromyographic, and computer simulation data are combined to show the relationships between acoustic, configurational, and muscular characteristics of vocal registers. [Work supported by NINCDS.]
Objective measurements of the singer's voice as a “damage risk” indication
Authors: Coleman R. F.
Published: October 2005

Professional singers, particularly beginning performers, seldom have any objective means to determine safe performance limits of their voices, and so must rely on trial and error experience to know what singing ranges are feasible for the individual. This almost invariably leads to vocal difficulty, ranging from simple laryngitis to chronic, profession threatening vocal pathology. This presentation will discuss normative data on the singer's voice, particularly with respect to the physiological and acoustic limits of the instrument measured in a “F0-SPL Profile.” Examples of professional performers' voice profiles will be used to illustrate the usefulness of the technique in estimating a type of damage risk criteria for voices.
Studies of pulmonary function and the singer
Authors: Gould W. J.
Published: October 2005

The relationship of the efficiency of pulmonary function to the singing voice was studied at a school for vocal training. The class in training was evaluated primarily by the period of time spent in studies of the individual groups under observation and then compared to professional singers. The residual pulmonary volumes were determined to be of highest importance in this assessment. This study then was correlated to experience with situations in which impairment of this pulmonary volume measurement existed, such as pulmonary asthma. The group of asthmatics in the singing profession was higher than that encountered in the average population group. The importance of these findings is primarily for the understanding of the physiology of the singing voice.
Reflection coefficients of upper ocean sound-speed variability
Authors: Kaye G. T. , Northrop J.
Published: October 2005

Profiles of temperature and conductivity with depth were measured at two-minute intervals in June 1977 off R/P FLIP at a position 100 nautical miles west of San Diego. The profiler was developed by R. Pinkel of the Marine Physical Laboratory for upper ocean internal wave measurements. From these data, acoustic reflection coefficients were calculated for angles of incidence near normal for acoustic impedance changes on a one-meter vertical scale. Coefficients of these reflective layers, which ranged from about −75 dB to less than −110 dB, were observed to vary slowly in the presence of high-frequency internal waves. It is suggested that acoustic remote sensing of these layers will be masked by biological reverberation interference. Comparisons between layer reflection coefficients and biological target strengths will be made to illustrate this point.
Acoustical studies of particulate dispersion in the ocean
Authors: Proni John R.
Published: October 2005

The question of accurate measurements of chemical or toxicant dilution rates in the ocean continues to be of fundamental interest to both the research and coastal management communities in the U.S. Results will be presented on the use of acoustical data to guide chemical sampling and reinforce chemical data on dilution rate estimates. Acoustical data will be presented which indicates the basic spatial variability scales of concentration of material dumped in the ocean for certain sites; the attendant implications for the statistical reliability of associated chemical data will be discussed.
Backscatter from small-seale oceanic sound-speed structure
Authors: Kaye G. T.
Published: October 2005

Remote sensing of oceanic sound-speed structure with acoustic backscatter measurements near normal incidence differs greatly from similar atmospheric measurements because of masking effects in the water column due to biological reverberation, With difficulty this can be overcome if one can achieve detection via a large-aperture array. Here considerable processing gain is available if one steers for curved wavefronts in the array nearfield, taking advantage of the curvature differences between returns from specular reflectors and discrete point scatterers. The field data suggest that sound-speed structures provide returns which are well-correlated in phase, although signal amplitudes for reflectors are less than returns from the point scatterers. Additionally, the data show that these reflectors are highly directional with beamformed returns dropping more than 15 dB as the angle of incidence varied to 2° off from normal. These characteristics indicate that acoustic remote sensing of oceanic sound-speed structure with high-frequency narrow-beam echosounders will be difficult because of biological reverberation interference, the anisotropy of specular reflectors, and source motion. Examples of data taken with an 87.5-kHz echosounder off R/P FLIP will be shown for this purpose.
Sodar observations in the Suez Canal zone
Authors: Fiocco G. , Mastrantonio G. , Ricotta A.
Published: October 2005

The ship SALERNUM on its way to and from the Indian Ocean for a GARP assignment crossed the Suez Canal twice and was briefly stationed at terminal points of the Canal and in the Bitter Lakes. The ship carried a monostatic sodar with Doppler capability. During both passages which took place in January and March the sodar was operated almost continuously, and standard meterological measurements were carried out. During the return passage a tethered balloon was deployed to provide temperature and humidity profiles, and a few pilot balloons were launched. The natural environment of the Suez Canal zone is somewhat unusual due to the presence of large and small bodies of water surrounded by desert. Very large spatial and temporal temperature and humidity contrasts exist which are not normally encountered elsewhere. A variety of boundary layer structures have been observed and analyzed.
Airborne noise criteria on naval ships: Estimating crew response
Authors: Lambert David R.
Published: October 2005

Graphs are presented for predicting the response of shipboard personnel to airborne noise when a given compartment type just meets a proposed A-weighted criterion. The graphs were constructed from the responses of personnel in selected compartments aboard eight U.S. Naval ships. The author used the responses to questions on habitability to rate each compartment on a five point scale ranging from satisfactory to unsatisfactory. These ratings were then plotted as a function of A-weighted sound pressure level, and parameters for the curves estimated. [Work sponsored by the Naval Sea Systems Command.]
The research and application of acoustic radar systems in Australia
Authors: Shaw N. A. , Bourne I. A.
Published: October 2005

Research and development of atmospheric acoustic radar systems have been closely supported by “application” programs associated with industrial needs. To study this interaction, a survey was conducted on (a) the nature and emphasis of acoustic research programs, (b) the degree of successful industrial application of various systems, and (c) the current and anticipated needs of industry for improved acoustic radar performance. Institutions involved in researching atmospheric acoustic radars include universities, colleges of advanced education, and defense establishments. The power, mining, and larger manufacturing industries have used acoustic probes mainly as a tool for either evaluating meteorological parameters conducive to air pollution problems or as part of extensive environmental impact studies. The somewhat qualitative records by single axis systems are still susceptible to interpretation difficulties. Classification of data, at least into categories and formats suitable for further digital analysis, has been sought, but now the greatest interest exists in multiaxis systems which are thought to be capable of measuring wind profiles and dispersion parameters to heights of 1000 m as well as retaining the conventional facsimile display.
Estimates of surface heat flux from sodar and laser scintillation measurements in the unstable boundary layer
Authors: Coulter R. L. , Wesely M. L.
Published: October 2005

Measurements of acoustic backscatter in the lower planetary boundary layer and optical line-of-sight scintillation in the surface layer are used separately to compute the sensible heat flux in the unstable surface layer. Comparisons with simultaneous low-level point measurements by eddy correlation show good agreement both in absolute magnitude and response to rapid changes, indicating that acoustic methods may be successful over less homogeneous terrain where conventional surface layer measurement techniques are often inaccurate. Corrections to lake into account the effects of humidity fluctuations are found necessary in order to achieve accuracies within 10%. Free convection is assumed to permit interpretation of the sodar data, while either forced or free convection is assumed for the scintillation data. A systematic overestimate of surface heat fluxes is found from acoustic measurements made during the morning when the convectively mixed layer is rapidly increasing in height. [Work supported by U.S. Dept. of Energy and U.S. Environmental Protection Agency.]
Low-level versus high-level amplitude compression
Authors: Nábělek Igor V.
Published: October 2005

Sensori-neural hearing-impaired individuals often exhibit a loudness function with a steeper slope at low levels than normally hearing people. At progressively higher levels the slope of the loudness function for the hearing-impaired approaches that of the normally hearing. Reducing the signal level differences at high levels (high-level compression, HLC) makes an abnormal loudness function, more so, while, reducing level differences at low levels (low-level compression, LLC) should result in a more normally appearing loudness function. CVC words (MRT) were processed under three conditions: (a) only levels between Lr −25 dB and Lr − 13 dB (Lr is the average maximal rms levels of the test words' vowels) were compressed (LLC) with a compression ratio CR = 4:1: (b) only levels above Lr −13 dB were compressed (HLC) with CR = 4:1: and (c) only levels above Lr −25 dB were compressed with the average compression ratio between Lr and Lr −25 dB in conditions “a” and “b” equal to 1.7. All three conditions had attack and release times of 1.5 and 30 ms. respectively. The performance of nine sensori-neural hearing-impaired subjects did not significantly differ among the three conditions investigated; this confirms Lippmann's (1978) findings with the compression system restoring normal equal loudness contours. [Work supported by NIH NS 12946.]
Speech perception for various time constants of amplitude compression
Authors: Nábělek Igor V. , Wood W. Scott , Koike Kazunari J. M.
Published: October 2005

Modified rhyme test words and CVC nonsense syllables were processed without or with background pink noise through a wideband amplitude compressor set for a 2.5:1 compression ratio and various attack (TA = 1 through 42 ms) and release (TR = 10 through 370 ms) times. These stimuli were presented to nine subjects with sensori-neural hearing impairment. The compression threshold was set 25 dB below the average maximal rms level of the vowels in the test words or CVC syllables. The compressed 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 same, comfortable level for each individual listener. The signal compressed without noise was sometimes mixed with a masking pink noise at − 10, − 5, and 0 dB re speech. There were no significant differences in mean performances for different time constants, or between compressed and noncompressed stimuli. Performance slightly increased with compression, only when masking noise was added to the signal after processing (Ls − Ls ⩽ 5 dB) and the attack and release times were shorter than 3 and 90 ms, respectively. [Work supported by NIH NS 12946.]
Temporal characteristics of the stapedial reflex with multiple sclerotic subjects
Authors: Schechter M. A. , Rupp R. R. , Calder H. B. , Milburn B.
Published: October 2005

An impedance technique has been employed to quantitatively compare the temporal characteristics of the stapedial reflex in seven normal subjects and seven subjects with multiple sclerosis. Measures of latency and rise time of the reflex were collected in both groups. Analysis of the results revealed significant mean group differences for both the latency and rise time measures. Eliciting stimuli were tone bursts of 25 ms (2.5 ms rise/fall) and tones with a duration of 1 second (2.5 ms rise/fall) at both 10 and 20 dB SL. Three of the seven multiple sclerotic subjects displayed latency or rise time measures that were two or more standard deviations above the mean. The remainder of the pathological group fell within “normal” limits. Aberrant reflex characteristics would only be expected in those multiple sclerotic subjects with demyelination occurring within the auditory pathways. [Work supported by the Veterans Administration Hospital.]
Further studies on the total-energy hypothesis
Authors: Ward W. D. , Kiester T. , Turner C. W.
Published: October 2005

Previous studies have established that in the chinchilla, the “critical level” for a 220-min continuous exposure to 700–2800-Hz noise is 105 dB SPL, in the sense that such an exposure produces neither significant permanent threshold shift (PTS) nor an increase in missing hair cells (MHC) over the normal median value of 50 to 100. However, 108 dB produced an MHC count of over 400, and 111 dB generated not only a 700-MHC count but also a 10-dB PTS at 2 kHz. Finally, 114 dB produced 1500 MHC and a 30-dB PTS at 2 kHz. Breaking the 114-dB exposure down to 22 10-mix exposures administered twice weekly for 11 weeks reduced the MHC count to just over 300, with negligible PTS at 2 kHz, implying a reduction in “effective exposure level” of about 7 dB. Two more related exposures are reported here. A continuous 2200-min (1.5-day) exposure at 102 dB SPL produced 950 MHC and l0 dB of PTS. which are values that would be predicted on the basis of the total-energy concept—i.e., equivalent to 112 dB for 220 min. On the other hand, a 440-min exposure at 114 dB SPL using a pattern of 30 s on, 30 s off (cumulative exposure 220 min), also produced essentially the same effect as 112 dB for 220 min (800 MHC, 20 dB of PTS). The results thus affirm the validity of the total-energy principle in assessing single uninterrupted exposures to noise, as in acoustic trauma, but also indicate that rest periods. even short ones, reduce the permanent effect of repeated exposures. [Work supported by NIH grant NS 12125.]
Predicting noise-induced threshold shift: A second look
Authors: Erdreich John
Published: October 2005

Several years ago we presented a pilot study in which measurements of cubic and quadratic nonlinearities were compared with measurements of TTS2 made on the same three listeners [J. P. Cobb and J. Erdreich, J. Acoust. Soc. Am. 60, S104 (1976)]. From the data we suggested a relationship between threshold shift and amplitude nonlinearity. In an extended study we have examined this relationship at three frequencies separated by octave intervals. Temporary threshold shift at 1.4 times the exposure frequency produced by a 12-min 500-Hz, 1000-Hz, or 2000-Hz pure tone at 90 or 100 dB SPL was measured in ten listeners. The amplitude of the combination tone f1 + fh (fh/f1 = 1.2; f1 = 500, 1000, or 2000 Hz) was measured for primary levels of 70 dB SPL. At 500 Hz the fatiguer produced little threshold shift. For the 1000-Hz exposures, the relation between TTS2 and auditory nonlinearity is yet supported. At 2000 Hz, the threshold shifts produced were highly variable, possibly the result of system resonances. This will be explored further. Although these results are consistent with other studies suggesting a mechanical determinant of TTS susceptibility, additional evidence will be presented suggesting that there is also a metabolic component of susceptibility. [Supported by Dept. of the Army DAMD17-78-C-8074.]
A critical level for auditory damage at high intensities
Authors: Price G. Richard
Published: October 2005

Evidence from a number of different studies in which the ear was exposed to intense sounds can be interpreted as showing that there is a critical level (Lc) above which the loss mechanism changes. Based on the research of Price [J. Acoust. Soc. Am. 66, 456–465 (1979)], the physiological basis for Lc is thought to be mechanical stress at the level of the hair cell. When measured with conventional instruments, Lc depends on the spectrum of the sound as well as its specific pressure-time history. For an exponentially damped 1 kHz impulse, Lc has been calculated to be about 145 dB for the median human ear and about 155 dB for a rifle shot. For the cat ear, Lc may be about 20–25 dB lower than for the human ear. The presence of a spectrum-dependent critical level resulting from mechanical stress in the inner ear has significance for efforts to limit hazard from intense stimulation. It suggests not only how intense a sound is acceptable; but also how it should be measured. In addition, the presence of species dependent differences in Lc also has implications for use of animal models in noise effects research.
A metric for the height of certain pitch peaks in English
Authors: Liberman M. Y. , Pierrehumbert J. B.
Published: October 2005

Subjects were asked to produce various utterances with a systematic variation of pitch range (thought of as “degree of overall emphasis”). These utterances each contained two main pitch accents; each utterance was considered as a possible answer to one of two different questions which effectively “foregrounded” either the first or the second pitch accent. We investigated the scaling of peak and valley F0 measurements as pitch range varied. Our conclusions: (1) for intonations of this type, there is a fixed, declining baseline independent of pitch range; (2) the equation, (FP − FB)/FB = k × (BP − BB)/BB, fits our data quite well, where FP is “foreground peak,” FB is the “baseline value at the location of the foreground peak,” BP is “background peak,” and BB is “baseline value at the location of the background peak.” That is, the ratio of foreground peak to background peak is constant when they are expressed in terms of baseline units above the baseline.
Vowel normalization and ear-canal resonance
Authors: Monsen R. B.
Published: October 2005

One male and one female subject spoke words of the form/h_d/ containing each of the English vowels. The words were recorded simultaneously in two different conditions: (a) in the free field, and (b) through an ear of an acoustic manikin (“Kemar”) fitted with a Zwislocki coupler. The recordings were transferred to disk for analysis by the Speech Microscope [Vemula et al., J. Acoust. Soc. Am. 65, S22 (1979)]. Each vowel was sampled at midpoint, and comparison was made of the waveforms and spectra in both recording conditions. The results indicate that, in Kemar's ear, the spectrum envelopes of front vowels have approximately the same shape above 2000 Hz for both male and female talkers, despite the fact that the actual formant frequencies may be very different. As Kemar hears it, the vowel /i/ has a single peak centered at 3000 Hz, which may correspond to F2 for females and Fa for males. For back and low vowels, the central peak in the spectrum is higher for females than for males. These results suggest that high-formant (front) vowels are partially normalized before they are “heard.” [Supported by NINCDS Grant NS03856.]
Jitter and shimmer as physical correlates of roughness in sustained phonation—Re-examination
Authors: Horii Yoshiyuki
Published: October 2005

Middle segments of sustained phonations [i, a, u] produced by 20 adult males were submitted to roughness magnitude estimation experiments by a panel of judges. The segments were also analyzed for mean fundamental frequency (f0), f0 standard deviation, jitter, and shimmer by an automatic f0 analysis program. The f0 analysis yielded an average jitter of 0.75% and an average shimmer of 0.38 dB. Multiple regression analysis showed that the roughness was most strongly reinled lo the mean f0. Contributions of jitter and shimmer to roughness, although statistically significant, were much smaller than expected from the near perfect correlations between roughness and jitter/shimmer reported by Wendahl (1966). Possible sources of this discrepancy and implications of the present findings are discussed. [This work is supported in part by the National Institute of Aging.]
A comparison of the frequencies of the peak energy of the first formant (F1) of the spoken vowel ā for two occupations
Authors: Jones J. M.
Published: October 2005

This study was based upon my hypothesis that a primitive sound language underlies human verbal language and communicates basic social, emotional, environmental, and task related parameters through physiologically encoded rules. A complicated thread of logic through the literature supported a prediction that the frequency of the peak energy of the first formant (F1) of the vowel ā would, therefore, be higher for a group of enlisted military personnel than a group of Ph.D. level managers or a group of nonmanaging engineers. The vowel ā was taped from 30 subjects, 10 from each group, and digitized. Using the fast Fourier transform, the amplitude frequency distribution was plotted. The F1 was significantly higher, as predicted, for the enlisted military group. This study was done as a masters thesis in psychology at the University of West Florida.
Is unequal temperament coming back for pipe organs
Authors: Hall Donald E.
Published: October 2005

For roughly a hundred years, equal temperament has been assumed practically without question for organs as well as pianos. But recently several organ builders have advocated unequal temperament, and put it into practice in their new instruments. Is this a minor aberration, or the wave of the future? First I will briefly review the unique acoustical problems presented by the pipe organ in choosing a temperament, and point out how past generations have coped with these problems. Second, I will report the results of a new survey of leading American organ builders. This will provide insight into the actual proportion of instruments now being unequally tempered, the reasoning and recommendations now being given by organ builders to prospective customers, and the prospects for unequal temperament to regain wide-spread importance. The author agrees with several of these builders that unequal temperament may deservedly have considerable importance and usage, yet without displacing equal temperament in the majority of church and concert-hall instruments.
An analytical model for the nearfield of a baffled piston transducer
Authors: Tjötta Jacqueline Naze , Tjötta Sigve
Published: October 2005

The linearized sound field from a baffled piston source (radius a, wavenumber k) in a dissipative fluid is considered. A simplified parabolic equation is derived (for ka ≫ 1) and solved analytically. The solution matches a plane collimated beam in the vicinity of the source and has the Bessel function directivity in the farfield. The nearfield-farfield transition region is studied. The range of validity of the parabolic equation is discussed. Its exact solution is shown to be the first term of an expansion in powers of (ka)−2 for the solution of the Helmholtz equation. The higher-order terms are secular at distances of order a(ka)1/3 from the piston. The analytical results obtained for the linearized field can be used to calculate the effects of nearfield oscillations on nonlinear effects generated in soundbeams. (For example, see Paper GG1, by the same authors, in this Program.) [Work supported in part by the Office of Naval Research.]
A formal operator solution for the scattering of sound by sound
Authors: Woodsum Harvey C. , Westervelt Peter J.
Published: October 2005

A general operator solution to the nonlinear acoustic wave equation for a viscous medium, [V2(1 + ρ0−1c0−2η∂∂t) − c0−2∂2∂t2]P = Q = −βρ0−1c0−9∂2∂t2 (P2) is obtained from perturbation series, P =  ∑ N=1∞ εNP(N); Q =  ∑ N=2∞ εNQ(N). The exact solution for P(N) ∼ 0(εN) is shown to be P(N) = (1 − exp{[|∂∂t||c0∇|−1(1 − 12ηρ0−1c0−2∂∂t) − 1]r⋅∇} × exp[−Re(r⋅∇)])[∇2(1 + ρ0−1c0−2η∂∂t) − c0−2∂2∂t2]−1⋅Q(N). This solution is a formal extension of Westervelt's 1972 nonsingular operator solution [J. Acoust. Soc. Am. 59, 760 (1976)] to the case of a medium with viscosity. The evaluation of the operator expression above is shown to be straightforward, provided the primary field P(1) is first expanded into a Fourier super-position of plane waves. Parametric array applications are discussed.
Preliminary results on observations of chinooks using a Doppler acoustic sounder
Authors: Leelananda S. A. , Hicks R. B. , Irwin P. J. , Mathews T.
Published: October 2005

An acoustic sounder array located on a rural site 20 km west of Calgary is described. The array is designed to sense atmospheric turbulence with a working vertical range of 2 km and also to provide information on the vertical wind profile up to 800 m above the site. The array consists of a central, vertically directed, monostatic array (output acoustic power ∼ 100 W), and four passive inclined receivers, each acting as a bistatic receiver for the central monostatic transmitter. The bistatic receivers are arranged along two mutually perpendicular horizontal baselines. On-line microprocessors are used to retrieve Doppler shift data from all receiver channels, and hence to calculate the wind profile. Typical results from the Doppler acoustic sounder array are presented. It is hoped that by the time of presentation, soundings will have been made during at least one Chinook event (a foehn-type wind associated with airflow over the nearby Rocky Mountains).
Comparison of acoustic scattering data with predictions from a second-order numerical model of the statistically stable boundary layer
Authors: Neff W. D.
Published: October 2005

We have utilized a simplified second-order turbulence closure scheme to predict acoustic scattering profiles as a function of time from a numerical model of the atmospheric boundary layer under statically stable conditions. Comparisons have been made with data obtained at South Pole Station, Antarctica. Two cases in particular were analyzed. The first was that of warm air advection over a cold surface. The second involved the thin boundary layer and elevated scattering layers that form when the geostrophic pressure gradient force opposes the thermally driven slope winds characteristic of the East Antarctic ice sheet.
An intercomparison of acoustic Doppler systems
Authors: Kaimal J. C.
Published: October 2005

During late August and early September 1979 the Boulder Atmospheric Observatory (BAO) was the site of an international comparison of low-level sounding techniques. Called the Boulder Low-Level Intercomparison Experiment (BLIE), its objective was to compare a wide range of sounding systems including free-rising sondes, tethered sondes, tower-mounted sensors, remotely piloted aircraft, and acoustic and electromagnetic remote sensors. Six acoustic Doppler systems were compared. This paper will describe procedures used for the intercomparison and offer some preliminary results showing how the systems compared with one another and with in situ wind measurement on the 300-m BAO tower.
A new approach to the solution of eigenvalue problems in circular flow ducts
Authors: Ko Sung-Hwan
Published: October 2005

Sound attenuation in acoustically lined circular ducts with fluid flow was investigated using a Taylor series method for the solution of the eigenvalue problem. The governing differential equation was numerically integrated across the duct cross section from the origin to the duct wall. The singularity of the differential equation at the origin was treated by analytically solving the differential equation valid only at the origin. Using values of the function and its derivatives at the origin, successive approximations of the eigenvalue were performed until the boundary condition at the duct wall was satisfied. Eigenvalues obtained by this method were compared with those obtained by a different method, and they were found to be in excellent agreement.
Medical management of hearing disorders
Authors: Clemis Jack D.
Published: October 2005

The auditory system consists of an outer, middle, and inner ear, the auditory nerve, and central auditory pathways. Each area has specific functions and each has diseases that impair that function. The purpose of this discussion is to present some of the more common diseases that afflict the auditory system and to discuss current techniques in diagnosis, medical/surgical treatment and unsolved problems that require continued research efforts.
Recent developments in hearing aid selection methods
Authors: Studebaker Gerald A.
Published: October 2005

During the past 30 years, research on hearing aid selection methods has been largely confined to evaluation of the speech-discrimination-test-based method first proposed by Carhart in 1946. Recently, however, an increasing number of researchers, and clinicians, alike, have concluded that a new iconoclastic and broad-ranging look at this problem area is required. Many of the proposals made recently are, in fact, based on proposals first made in the 1930's and 1940's. The new proposals and their origins will be reviewed along with developments of the past ten years that enhance the likelihood that one or more of these new methods will soon replace the speech-discrimination-test-based approach as the “standard” method for selection of hearing aids for the individual user.
Solving vibration and failure problems in prototypes
Authors: Peterson Edward L. , Knobeloch G. W.
Published: October 2005

In the early 70's, modal analysis was introduced as a powerful new tool for solving vibration problems. Animated mode shapes provided new insight into the dynamic behavior of mechanical structures. These tools gave the engineer guidance in how to modify designs to improve dynamic performance. But, to see the effects of proposed design modifications, prototypes had to be altered and reanalyzed. Now, technology has taken us one step further; recent software developments help us to foresee how proposed changes in the prototype will affect dynamic performance. The data generated by modal analysis is used to construct a system model. Then we analyze altered versions of this model. Thus, with this new software, the designer can choose the best of several alternatives before he physically alters the prototype.
The intelligent FFT system
Authors: Rothschild Richard S.
Published: October 2005

Vibration spectrum analysis is now performed using FFT computing devices almost exclusively. The digital nature of the FFT instrument has led to the incorporation of additional computational capability to enhance processing and interpretation. Much greater capabilities are becoming available through the marriage of computers and FFT analyzers, the most advanced of which are for modal analysis. The power and potential of a general or special purpose computer in combination with an FFT instrument-type analyzer is discussed with respect to typical vibration and acoustic problems that can be solved.
Strength and diffraction parameters in long-range sound transmission
Authors: Flatté Stanley M.
Published: October 2005

A method for calculating the strength and diffraction parameters, Φ and Λ is described. Floquet's theorem is shown to be of use in the calculation of Λ for a range-independent sound-speed profile. The sensitivity of Λ and Φ to changes in the sound-speed profile and the buoyancy-frequency profile is investigated. It is shown that rays with large intensity tend to have small Φ and small Λ except very near caustics. [Work supported by ONR Code 480.]
Transient wave propagation in bubbly liquids
Authors: Bedford A. , Drumheller D. S. , Kipp M. E.
Published: October 2005

Solutions for the pressure profiles of transient plane waves in a bubbly liquid have been obtained by using a finite difference procedure. In contrast to previous analyses, the liquid was not treated as incompressible. However, relative motion between the bubbles and the liquid was neglected. Two waves were clearly observable in the solutions. The first was a precursor wave in the liquid which had very little effect on the pressure in the bubbles. It was followed by a second wave in which the compression or expansion of the bubbles took place. An important finding was that the compressibility of the liquid had a substantial effect on the pressure profile of the second wave, which implies that the liquid compressibility should be included in future analytical studies of transient pulses in bubbly liquids. Comparison of the numerical solutions with the results of shock tube experiments [L. Noordzij and L. van Wijngaarden, J. Fluid Mech. 66, 115–143 (1974)] showed good agreement except that the solutions did not predict oscillations that were observed near the head of the pulse in the experiments. [Work supported by U.S. Department of Energy.]
Acoustic wave generation by vortex shedding
Authors: Bowline C. M. , Abbott W. Y.
Published: October 2005

It has been theorized that thrust perturbations observed in solid propellant rocket motors are caused in part by vortex shedding off flow obstructions (inhibitors), and the acoustic instability resulting from vortex flow between pairs of inhibitors. Acoustic measurements were made during wind tunnel tests developed to simulate flow between inhibitors. Results concerning geometric relationships and flow velocities are presented in this paper. In general, the flow between sets of baffles in a wind tunnel can create extremely large noises at predictable frequencies, given particular geometries and flow velocities.
The potential importance of correlated humidity and temperature variations for atmospheric acoustic back-scatter
Authors: McIlveen J. F. R.
Published: October 2005

The dependence of the velocity of sound on temperature and humidity mixing ratio is derived and the commonly applied expression of Wesley (1976) corrected. Variations in the acoustic refractive index produced by turbulent fluctuations in temperature, humidity mixing ratio and vapor pressure or density are examined. The resulting expressions are used in a simple approach to the structure function constant for acoustic refractive index. Wesley's (1976) conclusions (using expressions for structure constants in the surface boundary layer) about the relative importance of terms dependent on humidity structure are confirmed. The importance of the correlation between variations in temperature and humidity for the strength of echoes detected by monostatic sodar is discussed.
A simple scattering model for finite objects
Authors: Nelander J. C. , Matthews A. D.
Published: October 2005

A model for acoustic scattering from finite objects is described in terms of a three-dimensional Fourier wave space. This wave space representation, adapted from x-ray diffraction analysis, provides a convenient method for depicting aspect and frequency dependence simultaneously. Physical observables are interpreted by means of the Ewald construction. The method is illustrated for a rigid right circular cylinder. A procedure which eliminates mathematical difficulties which arise from surface discontinuities for finite objects when one-dimensional models are employed is discussed. Incorporation of impedance boundary conditions can alter details of the cylinder's scattering cross section. Examples are discussed and illustrated for aluminum and brass cylinders in water. Dominant observed features are related to the large phase shift which occurs at the shear critical angle. The model provides a useful simulation tool and also suggests a method for analyzing experimental data in detail.
Effects of neuropharmacological agents on auditory processing skills in young adults
Authors: Ludlow C. , Caine E. , Cudahy E. , Cardano C.
Published: October 2005

Two commonly used compounds (scopolamine and dextroamphetamine) well known for acutely manipulating brain function were administered to normal young adults 1 h prior to performing auditory tasks in a double blind placebo-drug crossover study. A gap detection task required the detection of brief periods of silence in noise using a forced choice procedure. A temporal order task required identification of order of a two tone sequence using a forced-choice procedure. Thresholds for both were derived from least square fitted psychometric functions. Scopolamine, an acetylcholine inhibitor, significantly increased the gap size detected at 75% threshold and increased the ISI at 75% threshold on the temporal order task. The effects of dextramphetamine, which augments catecholamine, mediated neurotransmission of brain arousal were much less dramatic. No change occurred on the gap detections functions while a very small effect towards improving the ISIs occurred on the temporal order task. Thus, increased brain arousal did not improve auditory processing skills while reduction in temporal lobe acetylcholine content adversely affected the processing of rapidly changing acoustic events.
The precedence effect revisited
Authors: Brandauer C. M. , Ward W. H.
Published: October 2005

In their now classical study of the precedence effect, Wallach, Newman, and Rosenzweig [Am. J. Psychol. 62, 315–336 (1949)] determined the interaural time difference of the first click pair (ITD1) needed to offset a fixed and opposite interaural time difference of a second click pair (ITD2) when the pairs were separated by a time interval short enough to yield a single, fused image. For several values of ITD2, they found that the indifference point, i.e., where “right” and “left” judgements were equally likely, occurred when |ITD2|/|ITD1| = 6. We have repeated their experiment at various sensation levels and found that the |ITD2|/|ITD1| ratio decreases from values greater than theirs at SL = 20 dB to nearly one at SL = 65 dB. The relationship of these results to earlier studies and some possible explanations will be discussed.
Infant and adult ear asymmetry differences for memory-based consonant versus vowel discriminations
Authors: Best Catherine T.
Published: October 2005

Recent evidence indicates that the adult REA for speech and LEA for music are present by 3 months. Yet the nature of perceptual asymmetries, and the effect of stimulus properties, in the infants' speech REA are unknown. The adult literature on perceptual asymmetrics suggests a possible left hemisphere mechanism for perception of consonants via reference to rapid articulatory gestures, since adults typically show REAs for consonants but not for vowels. Condition A of this study measured infant and adult ear asymmetries for discriminations among consonants versus vowels in CV syllables. Studies of associations between stimulus properties and adult ear asymmetries indicate special left hemisphere responsivity to transient information, e.g., rapid formant transitions. Therefore, Condition B assessed how removal of formant transitions from the CVs (phonemes remained identifiable) affected infant and adult ear asymmetries for consonant versus vowel discriminations. Results indicate adult asymmetries are largely perceptual, with left hemisphere phonetic perception for consonants but not vowels. However, acoustic factors apparently outweigh phonetic perceptual factors in infant speech REAs. Implications for brain-behavior relationships in perceptual development, especially speech perception, will be discussed. [Partially supported by NICHD and NINCDS.]
Detection of a tone below absolute or tone-masked threshold by interaural phase discrimination
Authors: Ayres Thomas , Clack T. D.
Published: October 2005

Binaural beating or changes in the threshold of an audible tone are sometimes reported when an inaudible tone is added to the contralateral ear. This study investigates a related effect using a two-interval forced-choice task. In this procedure, the subthreshold signal (800 Hz) is presented continuously to one ear; a probe tone (also 800 Hz, but at 10 dB SL) is presented in two pairs of short bursts (250 ms) to the contralateral ear. An interaural phase shift of 180° is introduced at the second burst of one pair, and subjects are asked to detect any change. Listeners usually hear these phase effects as variations in lateral position, even when the signal is 10 dB or more below its threshold (4 out of 6 subjects). One achieved above-chance performance with the signal at −15 dB SPL (−21 dB SL). Such results show that information regarding a subliminal monaural tonal signal may be transduced and available to the binaural-processing system even at such extremely low sound pressure levels. Similar results are found when the threshold is shifted by using a continuous tone as a masker (300 or 500 Hz at 60–75 dB SPL). These findings are strikingly different from those obtained with the masking-level difference paradigm.