bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of structureborne noise isolation systems on a lightweight ship foundation
Authors: Fox G. L. , Scharton Terry D.
Published: October 2005

Radiated structureborne noise from main propulsion machinery in a lightweight, high-performance craft is of concern. This is due to the conflicting requirements of human habitability and ship weight. Efficient structureborne noise isolation of the main machinery will reduce the weight of the acoustical treatment required in receiver spaces. Main machinery isolation involves the consideration of the mechanical vibratory interactions between the machine, subbase, and foundation as well as the elastic mountings that connect these components. This paper presents a method that allows an analyst to calculate the structureborne noise power transmitted into a structure composed of idealized finite length beams. Impedance relationships are developed for the machine, subbase, foundation, ship hull, and the intervening isolators. Idealized finite length beam impedances are derived for various boundary conditions. The results of a parametric study to assess the effectiveness of vibration isolators, for various system parameters, is presented for a ship hull of typical aluminum construction.
Wavenumber/frequency admittance of beams
Authors: Grosh Karl , Hughes W. Jack , Burroughs Courtney B.
Published: October 2005

Using an array of point drives, the admittance of finite beams were measured and compared to predictions. The predictions were made using an analytic model of the beam response based on Timoshenko beam theory. To drive the desired wavenumbers, the amplitudes of the point drives were weighted to produce standing wave patterns that were made up of left and right traveling waves, both of the same wavenumber. The standing wavepattern avoids the need to control the phases between the drives that would have been required for traveling single wavenumber drives. The effects of beam resonances are explored by comparing measured admittance data for beams with free ends, with and without internal damping and for beams with heavily-damped ends. The wavenumber/frequency transfer functions of resilient layers placed between the array of drives and the beam are determined from admittance measurements made with and without the resilient layer.
Two-microphone measurement of acoustic intensity in the ear canal as a calibration of high-frequency hearing
Authors: Murphy William J. , Tubis Arnold , Long Glenis R.
Published: October 2005

As an alternative to measures of ear canal pressure in the vicinity of the tympanic membrane, we propose an acoustic intensity measurement slightly downstream from the point of sound delivery as a convenient and meaningful calibration of high-frequency hearing. If sound absorption in the air medium and at the walls of the ear canal is neglected, the power flow through any cross section of the ear canal would be equal to the power flow into the middle ear. A sound delivery and intensity measurement system has been built using a two-port earmold. The tube of an Etymotic Research ER-2 sound delivery system passes through one port and a pair of probe tubes (outer diameters = 1 mm, tip separation ≈ 3 mm) pass through the other. The latter are connected to ER-7 microphones and used for acoustic intensity measurements based on a cross-spectrum algorithm. Data are given on the sensitivity of measurement results with respect to the relative positions of the sound delivery point and probe tube tips. [Work supported by a grant from the Deafness Research Foundation.]
Diffuse field response of the ear
Authors: Killion Mead C. , Berger Elliott H. , Nuss Richard A.
Published: October 2005

The ear canal pressure developed in a diffuse-field facility complying with ANSI S12.6-1984 was measured on 20 adult subjects (11 male and 9 female), with two replications on each ear for 19 of the 20 subjects. A soft 1-mm-o.d. silicone rubber probe tube was inserted until the subject reported the “thump” of the tube bumping the eardrum, and then withdrawn a couple of mm. Preliminary experiments indicated that this technique did not always produce the same results, with some curves on the same ear of the same subject showing substantially less “eardrum SPL” in the 8- to 20-kHz region than others. It was sometimes (but not always) possible to confirm with otoscopic examination that the lower-SPL curves corresponded to probe-tube locations away from the eardrum. Based on the preliminary experiments, data from the “best run of the best ear” (i.e., highest level above 8 kHz) were averaged. The resulting curve was similar to the curve obtained on a KEMAR manikin in the same sound field.
Reference threshold levels for the ER-3A insert earphone
Authors: Wilber Laura Ann , Kruger Barbara A. , Killion Mead C.
Published: October 2005

Two sets of provisional reference threshold sound pressure levels have been provided by the manufacturer for the calibration of the ER-3A insert earphone. One set is for use with the B&K DB-0138 coupler (an HA-2 2-cc coupler that comes with a 5-mm-diam by 2-mm-long stainless steel coupling nipple preceding the 18 mm of 3-mm-diam earmold-simulation portion specified in S3.7-1973), and the other set is for use with the HA-1 coupler (the standard “In The Ear hearing aid” 2-cc coupler) with a foam eartip sealed directly to the top surface of the coupler. Several recent studies have demonstrated that the ER-3A may be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone in some cases, but most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This paper reports the results of such a data analysis.
Temporary threshold shift after exposure to a narrow-band noise, frequency-modulated tones, continuously variable frequency tones and a pure tone
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Temporary threshold shift after exposure to four stimulating sounds were measured by automatic audiometry for three subjects with normal hearing. Stimulating sounds were (1) a pure tone, (2) continuously variable frequency tones between 1250 and 1750 Hz, (3) frequency-modulated tones centered at 1500 Hz with a frequency deviation of ± 250 Hz and a modulation rate of 25 per s, (4) a narrow-band noise with a bandwidth of 1250–1750 Hz. Subjects were exposed to stimulating sound through an earphone at the intensity of 110 dB SPL and duration of 10 min. Temporary threshold shift was measured for frequencies between 1000 and 8000 Hz beginning at 5 s after cessation of the stimulating sound. Results indicated that the greatest shift was observed at a frequency 2000 Hz by a pure tone stimulation and the least shift by a narrow-band noise. Effects of continuously variable frequency tones and frequency-modulated tones were intermediate. These findings were compared and discussed with temporary threshold shift following exposure to white noise at equivalent intensity and duration.
Effects of brief, intense tones on auditory temporal acuity
Authors: Champlin Craig A. , Feth Lawrence L.
Published: October 2005

A gap detection threshold (GDT) procedure was used to measure auditory temporal acuity in humans before and after exposure to a brief, intense low-(0.4-kHz) or high-(1.7-kHz) frequency tone. The maximal temporary threshold shift (TTS) produced by each exposure was approximately 10 dB. GDT stimuli were octave-band noises centered at one of three frequencies: the exposure frequency, 1/2 oct above the exposure frequency, or 1 oct above the exposure frequency. GDTs were obtained at 35, 55, and 75 dB SPL at each center frequency. GDT and TTS recovery were monitored for 16 min following an exposure. The results from the high-frequency exposure condition indicate that changes in GDT can be predicted from shifts in absolute threshold. For the low-frequency condition, difference between the GDT and TTS recovery functions and elevated GDTs in the absence of significant TTS require an alternative explanation. [Work supported by NIOSH.]
Predicting masked thresholds in impaired listeners from combinations of normal masked thresholds and hearing loss
Authors: Jesteadt Walt , Stelmachowicz Patricia G. , Callaghan Brian P.
Published: October 2005

Many studies have simulated sensorineural hearing loss using maskers that produce equivalent threshold elevations in normal listeners. This suggests that masked thresholds in impaired listeners can be viewed as a combination of the masking expected in normal listeners and the masking represented by the hearing loss. To test this hypothesis, we fitted simultaneous-masking data for five impaired listeners using recent models of combined masking. The data were levels of narrow-band noise maskers at several frequencies required to just mask 2000-Hz probes presented at 5 to 25 dB SL. For masker frequencies in regions of maximal abnormal upward spread of masking, the model correctly predicts that: (1) growth of masking is more gradual in impaired listeners, (2) the maximum difference in thresholds for normal and impaired listeners occurs when the normal listener's masked threshold is equal to the impaired listener's quiet threshold, and (3) the size of this difference increases with the degree of hearing loss. The last result suggests that sensorineural hearing loss can best be simulated with forward maskers. [Work supported by NIH.]
The shape and alignment of rising intonation
Authors: Steele Shirley A. , Liberman Mark Y.
Published: October 2005

Factors that affect the location of the nuclear stress F0 peak in statements have been described elsewhere, and the importance of correct peak placement in text-to-speech synthesis has been demonstrated [Steele (1986); Liberman and Steele (1986)]. This paper describes the temporal characteristics of the rising intonation pattern at the end of yes/no questions. In particular, certain questions of interest for text-to-speech synthesis have been asked: What parameters are needed to describe the shape of this F0 contour and its alignment with segments of the text? Specifically, how do the shape and alignment of the contour change with variations in the type and timing of post-nuclear segments and with changes in speech rate and pitch range?
Ultrasonic propagation properties of excessively high fatty rat livers determined with the scanning laser acoustic microscope
Authors: O'Brien William D. , Erdman John W.
Published: October 2005

The effects of 1% dietary orotic acid on the ultrasonic propagation properties of rat livers were examined. In rats, dietary orotic acid exerts several effects on lipid metabolism; its overall consequence is that excessively high fat concentrations are built up over a short period of time, thus making this an ideal model to study the ultrasonic propagation properties as a function of fat in liver. Over a 16-day period of time in which the rats were on the orotic acid diet, lipid concentrations increased from a normal range of 2%–4% to the lower 20's%. Additionally, water concentration decreased from normal values of approximately 70% to approximately 50%. Total protein concentration decreased slightly from a normal of 17%–20% to 11%–16%. The rat liver weight increased from approximately 11 g to around 20 g. Ultrasonic attenuation coefficient and speed were assessed with the scanning laser acoustic microscope at 100 MHz. Strong correlates of ultrasonic speed with both water concentration and fat concentration in the liver were observed. Multivariant linear regression was used in the analysis of covariance to fit the least-squares estimates to the linear regression model.
Human gallstone dissolution accelerated by ultrasound application
Authors: Fry Francis , Sanghvi N. T. , Burney Bryan , Griffith S. , Hastings J. , Franklin T. D.
Published: October 2005

Gallstones in appropriate chemical species subject to ultrasound exposure show accelerated dissolution over that accruing to the chemical alone. In vitro studies using a human gallstone submerged with monooctanoin (a cholesterol stone solvent) in a latex envelope show dissolution of a stone mass of 0.50 g with 6 min of total ultrasound exposure at a SPTP intensity of 15 W cm−2. Control stones in the monooctanoin show a weight loss of 0.05 g in the same overall treatment time. When a pressure of 350 lb in−2 is applied the stone dissolution rate declines by a factor of 3 from that at atmospheric pressure. The primary erosion mechanism is apparently of cavitation origin but a smaller but significant erosion acceleration occurs in the apparent absence of cavitation. A unique feature of this type of gallstone dissolution is the conversion of solid stone into a liquid state providing for ease of passage of gallbladder content in the clinical situation. That this accelerated dissolution occurs in vitro has been demonstrated on a series of pigs with human gallstones implanted in their gallbladder. [Work supported by Indiana Corporation for Science and Technology, I. C. F. A. R., and Labeco/Labsonics, Mooresville, IN.]
Space-time processing, environmental-acoustic effects
Authors: Carey W. M. , Moseley W. B.
Published: October 2005

The processing of acoustic waveforms by arrays requires an understanding of the temporal and spatial characteristics of signal and noise fields. Temporal and spatial processing schemes are analogous transforms that can employ a variety of windows (such as Hann, Hamming, etc.). However, the ocean environment is a filter that introduces variability to a signal in both spatial and temporal domains. This randomness is superimposed on an ambient sound channel characteristic. In the case of static source and receiver combinations, the limits on horizontal broadside array resolution are due to volume scattering and surface scattering as long as the time scale is less than the signal correlation time. However, in the case of a moving source-receiver, the temporal and spatial scales are coupled through the sound channel characteristic and the fluctuation effects due to multipath or modal variations must also be considered. This paper reviews fundamental environmental effects and their influence on arrays in the deep ocean sound channel. [Work performed while at NORDA.]
Performance of sinusoidally deformed planar arrays
Authors: Leclere James H. , Del Balzo Donald R. , Caveny Deanna M. , Ioup George E. , Becklehimer Jeffrey L. , Murphy Donald A.
Published: October 2005

The investigations of Caveny et al. [J. Acoust. Soc. Am. Suppl. 1 80, S26 (1986)] are extended for the cases of horizontally and vertically towed planar arrays. Horizontal and vertical arrays of three lines (64 hydrophones each) and nine lines (28 phones each) are included. In addition, a nine-line array with five horizontal and five vertical lines (with the middle line of each in common) is also examined. Horizontal sinusoidal deformations of one-half cycle (and in some cases two and three half-cycles) are applied to each line. Complex pressure fields are modeled for various source directions for each array using the code BEAMSTATPAK of Collier (private communication). Beamforming is then done with the known array configuration and with the assumption that the array is planar (for selected cases). Degradations resulting from assuming planarity and the ability to remove left/right ambiguity are summarized as a function of the source location and the amount of array deformation in terms of reduced gain and angular resolution. Array performance is also examined in the presence of a realistic vertical noise distribution. [Research sponsored by NUSC.]
Determination of the mechanical limits of piezoelectric transducers using the finite element method
Authors: Dubus B. , Debus J. C. , Decarpigny J. N. , Morel D. , Boucher D.
Published: October 2005

The mechanical limit of ultrasonic transducers is associated with the fracture, nonlinearities, and fatigue strength of the different materials and thus is directly related to the distribution of stresses over the structure. The static case corresponds generally to the design of depth transducers and prestressed ceramic stacks. The dynamic case concerns high-power sonar transducers, as well as macrosonics. For several transducers, the stress field has been computed with the help of a finite element modeling, using the ATILA code [J. N. Decarpigny et al., J. Acoust. Soc. Am. 78, 1499 (1985)]. This paper describes such an analysis in the case of an axisymmetrical length expander transducer and a flexural shell sonar transducer [B. Hamonic et al., J. Acoust. Soc. Am. Suppl. 1 80, S26 (1986)]. The static stresses distribution is found when a mechanical bias is applied and maximum dynamic stress zones are identified at several frequencies, using a classical fatigue criterion. Measurements with strain gauges display a satisfactory agreement with computed results.
On multichannel sampling using only past samples
Authors: Brown John L.
Published: October 2005

A deterministic signal bandlimited to the normalized frequency interval − π < ω < π is completely determined by its sample values taken at the Nyquist rate of one sample per second. It is well known that if the signal is processed in parallel by m “independent” linear time-invariant filters (channels), then the signal may be recovered from samples taken at the m samples per second over all time. Here, the more realistic problem of estimating x(t) at a generic time t from the multichannel outputs sampled at only past sampling points {t − nT} is considered. It is shown that if the m channel outputs are all sampled at the same rate of 1/T samples per second, where 0 < T < m, then x(t) is uniquely determined from the channel output samples taken at the past times {t − nT}. Moreover, the condition required of the channel transfer functions to assure this result is the same as that required when the samples are taken over the doubly infinite time interval.
Timing in music: Performance and experience
Authors: Gabrielsson Alf
Published: October 2005

The only variable over which a music performer has practically complete control, regardless of which instrument he uses, is the duration of the sound events, as well as of “nonsound” events. Timing may therefore be considered as the most important tool available to the performer. Generally seen, timing can be related to four different phenomena: tempo, different classes of durations, articulation, and deviations from mechanical regularity. The musical score provides only limited information about all these aspects. Empirical studies of music performances reveal that the variations in these variables are much larger and much more frequently occurring than what is usually realized. They are used in order to influence the listener's experience of the music with regard to the perceived structure as well as regarding the motional-emotional qualities of the music. The systematic investigation of these questions is only in its initial stage and faces many difficulties, not the least concerning the proper ways of identifying and measuring the suggested experiential variables. Examples will be given from ongoing research.
Expressive microstructure in music: A first assessment of “composers' pulses”
Authors: Repp Bruno H.
Published: October 2005

According to a provocative theory set forth by Manfred Clynes [most recently in Cognition and Communication 19, No. 2 (1986)], there are composer-specific patterns of (unnotated) musical microstructure that, when discovered and realized by a performer, help to give the music its characteristic expressive quality. Clynes, relying on his own judgment as an experienced musician, has derived such “pulses” for several famous composers by imposing time-amplitude warping patterns on computer-sythesized classical music. To conduct a formal perceptual asessment of four such pulses, two sets of piano pieces by Beethoven, Haydn, Mozart, and Schubert, one in triple and the other in quadruple meter, each synthesized with each composer's pulse plus a “neutral” version, were obtained from Clynes and presented in random order to listeners of varying musical sophistication for preference judgments. The results show reliable changes in listeners' pulse preferences across different composers' pieces, which supports one essential prerequisite of Clynes' theory. However, there were some significant deviations from the predicted perference patterns. Possible causes will be discussed. [Work supported by NIH-BRSG.]
Phonetic labeling and acoustic correlates for building Japanese speech data base
Authors: Sagisaka Yushinori , Katagiri Shigeru , Takeda Kazuya
Published: October 2005

Fine description of a large amount of speech signals is indispensable to acquire effective acoustic-phonetic rules in speech synthesis and recognition. To build a finely labeled speech data base, manual labeling is carried out using digital sound spectrograms and additional acoustic parameters that reflect power and spectral characteristics. Through labeler training, labeling items are modified several times to decrease the deviation of segment boundaries and to hasten labeling speed. As a result, not only the usual phonemic categories, but also finer phonetic events (e.g., closure, burst, and aspiration for plosive consonants) are labeled. Moreover, multiple segment boundaries (e.g., boundaries between vowels and following fricative consonants) and inseparable portions (e.g., aspiration followed by a devocalized vowel) are specially marked. To ensure labeling quality, reliability tests and error analysis are carried out. Labeling criteria using these results will be used for a large scale data base construction.
Speaker-independent vowel classification based on fundamental frequency and formant frequencies
Authors: Hillenbrand James , Gayvert Robert T.
Published: October 2005

A multivariate distance measure (MVD) was tested on a data base consisting of hand-measured fundamental and formant frequency values from ten English vowels produced by 29 male talkers and 27 female talkers. The primary purpose of the study was to determine what set of parameters produced the best classification performance. Results included: (1) classification accuracies as high as 90% were obtained using exclusively internal information (i.e., only acoustic measurements of the unknown token); (2) classification accuracies as high as 95% were obtained when internal information was combined with information describing the talker (e.g., average formant frequencies); (3) parameter sets using absolute formant frequencies performed better than sets using formant ratios or log formant distances; (4) a very small decrement in performance (1.1%) was observed when MVD was tested under conditions of no overlap between the talkers used to train the system and the talkers used to test the system; and (5) MVD did not need to be trained separately on male and female talkers. [Work supported by the Air Force Systems Command, Rome Air Development Center, and the Air Force Office of Scientific Research, Contract No. F30602-85-C-0008.]
Acoustic phonetic representations for continuous speech recognition: Networks versus lattices
Authors: Brennan Robert A. , Phillips Michael S.
Published: October 2005

A lattice has been used to represent the acoustic phonetic hypotheses in the Carnegie Mellon speech recognition system. This lattice was produced by four separate modules. Each module independently located and classified a set of target segments. A network representation is now being used that explicitly defines allowable paths through the phoneme hypotheses. The network has two advantages over the lattice representation. First, acoustic phonetic information can be used to join segment hypotheses. Second, a network allows the use of context-specific phonetic classification. Initially the network has been produced from the lattices using acoustic rules and broad classification information to connect segments, to adjust boundaries between segments, and to fill in gaps between the segments. Context-specific classification is now being developed for phones that are particularly sensitive to context effects. This network representation is being evaluated in the framework of the overall Carnegie-Mellon system. A comparison of the network representation with the lattice representation will also be presented. [Work supported by DARPA.]
Evaluating spectral distance measures with reference to human perception
Authors: Kane-Esrig Y. , Streeter L. A. , Karore C. , Devlin S. , Macchi M.
Published: October 2005

Two important criteria for spectral distance measures in automatic speech recognition are: (1) the variance of distances between different tokens of the same utterance should be small and variances of distances between different utterances large, and (2) the pattern of distances across utterances should correlate with perceived phonetic similarity of the utterances. These criteria were used to evaluate several spectral distance measures, including (1) Euclidean distance between two log formant ratios, (2) LP-residual (“Itakura”) distance, (3) Manhattan distance between linearly spaced points on LP spectra, and (4) Manhattan distance between points on “perceptual” spectra (transforming the frequency scale to barks and convolving with an asymmetric filter of critical bandwidth). Distances were computed among synthetic utterances and among one speaker's natural utterances of 11 Dutch vowels produced in isolation. The perceptual similarity data were those reported by Pols, van der Kamp, and Plomp [J. Acoust. Soc. Am. 46, 458–467 (1969)]. Not surprisingly, Euclidean distances between log formant ratios predicted perceived similarity best, but this measure is of limited practical utility, since formant tracking is problematic. The second best measure for both evaluation criteria was distance between “perceptual” spectra. Distance calculations using these “perceptual” spectra are computationally feasible, produce the desired spread in intervowel distance distribution, and mimic perceived similarity.
The Indiana Speech Training Aid (ISTRA): First year report
Authors: Kewley-Port D. , Watson C. S. , Elbert M. , DeVane G.
Published: October 2005

The ISTRA systems [Watson et al., J. Acoust. Soc. Am. Suppl. 1 81, Abstract OO14 (1987)] are used to improve the speech of deaf or misarticulating children, by providing unidimensional feedback based on acoustic information distributed over whole words or other utterances. This approach differs from that of many previous aids in which feedback was based on measures of single acoustic dimensions, or others that provided spectrographic displays. Using software developed over the first year of the project, the clinical effectiveness of ISRA drill has been evaluated for several deaf and one normal-hearing, misarticulating child. The research emphasis has not been on comparisons between the progress of training with a teacher and that with the ISTRA system, but rather on demonstrations that ISTRA drill is itself an effective training method. In these studies, listener juries rate the speech of words collected before, during, and after training. Results show significant improvement of the quality of words trained in the ISTRA drill, as well as generalization to nontrained words. These and other results demonstrating the improvement of articulation after drill on the ISTRA systems will be presented. [Research supported by NSF.]
Mechanisms of sound-producing instabilities of choked round jets impinging on small and large flat plates
Authors: Powell Alan
Published: October 2005

At the 112th Meeting certain characteristics of the discrete tones emitted when a choked round jet impinges on a normal flat plate were reported [J. Acoust. Soc. Am. Suppl. 1 80, S9 (1986)]. These are now shown to be one of two classes, dependent on whether the plate is small or large. If small (≅ orifice diameter D), the action occurs when the stand-off shock-wave is in a pressure recovery region of the spatially periodic jet structure, as in a Hartmann resonator, and the frequency overlaps those of a Hartmann resonator, successively excited at high harmonics. If large (> 4D), feedback to the orifice occurs, with up to seven frequency jumps not correlated with the periodic jet structure: f = c0(h + h′) N(1 + Mcon−12), 1 ≲ N = integer; ≲ 8, where N ≅ h/D + 3/2 (2<N<8) for the principal frequencies, c0 is the ambient sound speed, h is the orifice-plate distance, h″ is a constant ≅ 4D/5, and Mcon is the jet instability convection Mach number. These are almost independent of jet velocity and plate size, differing significantly in character from the subsonic case.
A time-frequency domain representation of sound energy by use of Wigner distribution
Authors: Suzuki Hideo , Kawaura Jun'ichi , Ono Takahiko
Published: October 2005

A time-averaged sound intensity is calculated from the crosspectrum of pressure outputs p1(t) and p2(t) of two closely located microphones. A major drawback of this sound-intensity measurement technique is that it is not applicable to a transient sound. This problem may be solved by use of the Wigner distribution that, roughly speaking, represents an energy density in the time-frequency domain when it is applied to proper functions of time or frequency [T. A. C. M. Classen and W. F, G. Mecklenbräuker, Philips J. Res. 35, 217–250 (1980)]. The cross-Wigner distribution of the pressure p(t) and the particle velocity u(t) (in the direction of interest) is obtained from the cross-Wigner distribution of p1(t) and p2(t) such as Re[Wpu (t,ω)] = −Im [Wp1p2 (t,ω)]/ω ρd, where d is the microphone distance. Results of the application of the cross-Wigner distribution to several transient signals captured by a microphone probe used for the conventional sound-intensity measurement will be reported.
Echoes from hills
Authors: Pierce Allan D. , Chen Pei-Tai
Published: October 2005

The question is raised as to whether echoes from hills are caused by reflection, scattering, or diffraction. In a typical situation when echoes are heard from a distant hill, it is impossible to construct a geometrical acoustics path that connects source to hill to listener and yet for which the angle of reflection equals the angle of incidence at the hill's surface. If the hill is modeled as a trapezoid, then the echoes are diffracted waves that originate at the baseline (where hillside meets level ground) and at the hilltop edge (where hillside meets hilltop). For hills with a continuously curved surface, the curvature radius is much larger than the wavelength, rigorous wedge diffraction theory is inapplicable and, moreover, the previous formulations of the geometrical theory of diffraction by curved surfaces also seem inapplicable because they account for diffraction effects only on the shadow side. Recent work by Medwin and others also suggests that the validity of physical optics approximations is questionable. In an attempt to understand the general physics of hill echoes, the classic rigorous solution for cw plane-wave incident on a hard parabolic cylinder has been studied. The contour integral with Whittaker functions in the integrand is approximated in the high-frequency limit for remote points back toward the source. [Work supported by NASA Langley Research Center.]
Effects of site geometry on noise control investigated by a scalemodel experiment
Authors: Kurra Selma
Published: October 2005

The geometrical parameters of a building and building groups were simulated in a scale-model study in which a miniature air-jet source moving along a channel in a semianechoic room was used. The scale factor was 20:1 and the frequency range was chosen between 1.2–20 kHz, corresponding to 63–1000 Hz of a traffic noise spectra. The noise generated by the source pass-bys was recorded at 2.8-s intervals and analyzed with the aid of computer programs to obtain time/level distributions in various points in the site model, and to determine the overall and spectrum levels of the line source, by also taking into account the typical spectrums for light and heavy vehicles, air absorption, and microphone directivity. After the validity tests of the technique, the effect of multiple reflections from buildings of different heights, variation of gap size between blocks, and dimensions of barrier buildings and their location angles were studied. The correlations and regressions between the physical dimensions and the noise levels were demonstrated. The results were confirmed by the earlier results of some theoretical and experimental investigations. The further evaluations yielded some simple but useful relationships to estimate the noise propagation in urban environments, for the designer's use especially in noise mapping, which requires a large number of noise data. [The scale-model study was carried out at Purdue University, R. W. Herrick Laboratories, with the consultation of Dr. M. Crocker (1981-82).]
Plans for a before and after study on community response to traffic noise
Authors: Gjestland Truls , Solberg Sigurd
Published: October 2005

Major changes in the road traffic pattern will be implemented in Oslo in the near future. A multidisciplinary field study has been planned to assess the impact on the community concerning social, medical, and behavioral effects. More than 1000 dwellings will be affected. [n the test area new by-passes/tunnels, traffic calming, and traffic management schemes, as well as facade insulation, will be introduced. The plans for describing changes in the noise exposure situation and the community response to these changes will be discussed.
Nonuniqueness of solutions to variationally formulated acoustic radiation problems
Authors: Wu Xiao-Feng , Pierce Allan D.
Published: October 2005

Determination of surface acoustic pressure when the normal velocity is prescribed over a vibrating body's surface can be formulated in various ways, but for some such formulations the solution is not unique at certain discrete frequencies. The question arises as to whether uniqueness problems are present for variational formulations of this problem. The answer is ordinarily “yes,” but proper selection of the variational approach can help to circumvent such difficulties. The variational formulation based on the normal derivative of the Kirchhoff-Helmholtz integral has a unique solution for vibrating disks and platelike bodies. For bodies of finite volume, but for which each surface point is vibrating in phase, calculated total radiated acoustic power is always unique, even though the pressure may not be. Use of the Gerjuoy-Ran-Spruch technique and judicious choice of what physical quantity is stationary under variations leads to a formulation such that the surface pressure is unique for any specified frequency. Similarities with the Burton-Miller techniques are discussed; an appropriate variational formulation provides a method for choosing the weighting factor for the linear combination of the two surface relations (an integral equation and an integrodifferential equation). [Work supported by ONR.]
Determination of Biot-Stoll pore-size parameter using high-frequency backscattering
Authors: Williams Kevin L. , Hackman Roger H. , Trivett D. H.
Published: October 2005

Calculations utilizing a Biot-Stoll model require knowledge of the pore-size parameter of the sediment. This parameter is difficult to obtain even from in situ measurements. Recent experiments using a broadband, high-frequency (0.5–2.5 MHz) pulse incident on a water-sediment interface at angles from 15°–45° (relative to the interface) indicate the possibility of determining this parameter remotely. When the spectrum of the backscattered signal is normalized to that of the incident pulse, an enhancement characteristic of the pore-size parameter becomes apparent. The spectrum shows a gradual rise in amplitude with increasing frequency followed by a decline whose rate depends on the physical parameters of the sediment being examined. Typical results will be shown for several sediments, along with a phenomenological model that recaptures the general features of the experimental results. The model displays the underlying physical effects that should be accounted for in a more comprehensive theory. Included in the model are contributions to scattering from both sediment grains and sediment channels. Also included is a “cutoff” of the channel contributions due to the acoustic scattering cross section of the grains exceeding their geometrical cross section. [Work supported by ONR.]
Pore-fluid wave propagation constants in stacks of low-flow resistivity glass beads
Authors: Sabatier James M. , Bass Henry E.
Published: October 2005

Measurements of the attenuation and phase speed of the pore-fluid wave were made in air-filled unconsolidated stacks of glass beads in the frequency range, 1–10 kHz. Glass bead sizes ranged from 1–10 mm. The experimental apparatus consisted of a 0.25-m-diam aluminum tube. A 0.25-m-diam capacitance transducer was operated in a pulse-echo mode at one end of the tube. At the other end, various depths of glass beads could be supported by a rigid plate. Multiple echoes from within 10–30-cm-thick stacks of beads could be observed. The measured propagation constants are compared to those predicted by the rigid porous frame theory [K. Attenborogh, J. Acoust. Soc. Am. 81, 93–102 (1987)]. [Work supported by WES.]
The use of CHIEF to obtain unique solutions for acoustic radiation using boundary-integral equations
Authors: Seybert A. F. , Rengarajan T. K.
Published: October 2005

This report is concerned with the problem of obtaining a unique solution for radiation problems at characteristic wavenumbers when a boundary-integral equation formulation is used. It is shown that the combined Helmholtz integral equation formulation (CHIEF) method works even when numerous interior points lie exactly on nodal surfaces of a mode corresponding to an eigenfrequency of the related interior problem, when at least one interior point does not lie on a nodal surface. The use of CHIEF is illustrated with numerical radiation experiments for the sphere and the finite cylinder. CHIEF is compared to the Helmholtz gradient formulation (HGF) for circumventing nonuniqueness and is found to yield a more accurate solution, in at least one published example. A procedure is used to indicate the solution error when using integral equation methods, with or without a technique to circumvent nonuniqueness. This procedure uses the velocity potential of an interior point as an indicator of solution error. In all cases considered, the interior potential correctly indicated a good or bad solution, whereas the matrix condition number falsely indicated a bad solution in several instances. [Work supported in part by ONR.]
Critical test of Gaussian beam method for multiply reflected fields in a surface duct
Authors: Niver E. , Ruiz C. J. , Vogas M. S. , Felsen L. B.
Published: October 2005

The Gaussian beam method (GBM) has found wide application in seismology for charting high-frequency wave propagation through heterogeneous environments. Unlike ray fields, Gaussian beams negotiate convergence zones without requiring caustic corrections. Because of these attributes, GBM may be useful also for sound field propagation in a realistically range- and depth-dependent ocean. However, in its conventional and facile implementation via a discretized stack of paraxially approximated beams, GBM is not a discipline with a priori predictive capability. By comparison with various canonical test problems, the accuracy of GBM has been found to depend strongly on the choice of arbitrarily assignable beam and stacking parameters. Here, the method is tested on previously not investigated multiply reflected fields in a range-independent duct bounded by a rigid bottom. The fields on the boundary are computed by asymptotic ray theory (ART), GBM, and by a rigorous generalized ray integral whose numerical evaluation serves as a reference. It is found that a beam stack “tuned” for accuracy along a ray that has undergone a given number of reflections becomes successively less accurate as the observer moves to a ray segment with a lesser or greater number of reflections. Retuning removes this deficiency but requires again a reference result for comparison. This circumstance illustrates again the basic difficulty with GBM. Possible spectral remedies [Lu, Felsen, and Ruan, Geophys. J. R. Astron. Soc. (1987)] are discussed, but they are less readily computable. [Work supported by NJIT and ONR.]
Effect of masker bandwidth on the detection of signals at unexpected frequencies
Authors: Dai Huanping , Scharf Bertram , Buus Søren
Published: October 2005

In wideband noise, listeners tested with the probe-signal method [G. Z. Greenberg and W. D. Larkin, J. Acoust. Soc. Am. 44, 1513–1523 (1968)] detect a signal at an expected frequency (primary) while missing signals at a far, unexpected frequency (probe). The present experiments test the hypothesis that the internal filter is narrowest at the primary frequency, thereby admitting less external noise there. According to this hypothesis, the probe should be as detectable as the primary when the external masker is narrower than the internal filter. Against wideband noise, subjects detected a 1-kHz primary on 90% of the trials and a 2-kHz probe on 60% of the trials. Against two simultaneous subcritical noises—one at 1 kHz, the other at 2 kHz—results were similar. With the noise at 2 kHz narrowed to 50 Hz, 6 of 12 subjects detected the probe reliably, possibly because the strong pitch of the masker drew attention to the 2-kHz probe. Overall, these results suggest that attention does not affect the width of the internal filter. [Work supported by NIH.]
Detection in noise by spectro-temporal pattern analysis
Authors: Hall Joseph W. , Haggard Mark P. , Fernandes Mariano A.
Published: October 2005

Detectability of a 400-ms, 1000-Hz pure-tone signal was examined in bandlimited noise where different spectral regions were given similar waveform envelope characteristics. As expected, in random noise the threshold increased as the noise bandwidth was increased up to a critical bandwidth, but remained constant for further increases in bandwidth. In the noise with envelope coherence however, threshold decreased when the noise bandwidth was made wider than the critical bandwidth. The improvement in detectability was attributed to a process by which energy outside the critical band is used to help differentiate signal from masking noise, provided that the waveform envelope characteristics of the noise inside and outside the critical band are similar. With flanking coherent noise bands either lower or higher in frequency than a noise band centered on the signal, it was next determined that the frequency relation and remoteness of the coherent noise did not particularly influence the magnitude of the unmasking effect. An interpretation in terms of nonsimultaneous masking was reconciled with some aspects of the data, and with an interpretation in terms of across-frequency temporal pattern analysis. This paradigm, in which detection is based upon across-frequency temporal envelope coherence, was termed ‘‘comodulation masking release.’’ Comodulation offers a controlled way to investigate some of the mechanisms which permit signals to be detected at adverse signal-to-noise ratios.
The perceptual reality of tone chroma in early infancy
Authors: Demany Laurent , Armand Françoise
Published: October 2005

It has often been advanced that pitch is a two-dimensional perceptual attribute, its two dimensions being: (1) tone height, a perceptual quality monotonically related to frequency; and (2) tone chroma, a quality shared by tones forming an octave interval. However, given that many musically uneducated adults do not seem to perceive tone chroma, this model is controversial. We investigated the sensitivity of three-month-old infants to tone chroma by means of a behavioral habituation–dishabituation procedure. Infants were presented with two successive melodic sequences of pure tones, the second sequence being a distorted version of the first one. The distortion consisted in shifting the frequency of some of the original tones, through a seventh or a ninth for some infants, through an octave for others. In the former case, infants displayed significant novelty reactions. In the latter case, significant novelty reactions were observed when the two sequences differed in melodic contour, but not when they had the same contour. These results suggest that young infants are sensitive to both tone height and tone chroma, and thus that tone chroma perception does not necessitate some form of musical experience.
Lateralization and frequency selectivity in normal and impaired hearing
Authors: Buus So/ren , Scharf Bertram , Florentine Mary
Published: October 2005

The onset-time difference ΔT required to lateralize a 30-ms bifrequency tone burst toward the leading ear was measured as a function of the frequency difference ΔF between the tone in the left ear and the tone in the right ear. At center frequencies of 0.5 and 4 kHz, four normal listeners tested at 80 and 100 dB SPL had ΔTs that were relatively constant at subcritical ΔFs, but increased at ΔFs wider than a critical band. At 1 kHz, ΔT increased with ΔF even at subcritical ΔFs. Ten listeners with cochlear impairments were tested at 100 dB SPL. Seven had normal ΔTs at 4 kHz, despite hearing losses between 50 and 70 dB. At 0.5 and 1 kHz, mildly impaired listeners had nearly normal lateralization functions, whereas more severely impaired listeners had very large ΔTs and no frequency selectivity. These and other findings indicate that listeners even with moderate to severe hearing losses can lateralize normally on the basis of interaural differences in onset envelope, but not on the basis of temporal differences in the fine structure.
The critical interval in dolphin echolocation: What is it?
Authors: Moore P. W. B. , Hall R. W. , Friedl W. A. , Nachtigall P. E.
Published: October 2005

A backward masking function relating target detection to masker delay was generated for a bottlenosed dolphin in an active echolocation target detection task. The masker was triggered by each outgoing echolocation click and could be temporally adjusted from coincidence with the target echo to delays of 700 μs. The animal reported target condition using a go/no-go response procedure. A modified method of constants was used to present the four masking delay intervals. Results indicated that 700- and 500-μs delays had little effect on target detection. However, as the delay was reduced to 100 μs, detection dropped to chance performance. The calculated 70% detection threshold corresponded to a delay of 265 μs. The results are discussed in support of the view that time separation pitch (TSP) may be an analytic mechanism used by the dolphin to discern various within-echo target attributes rather than an analytic mechanism for determining target range.
Relation between cubic-difference-tone generation and suppression
Authors: Norton Susan J. , Weber Daniel L.
Published: October 2005

Two aspects of the relation between cubic-difference-tone (CDT) generation and suppression were investigated in normal hearing listeners. First, the effects of narrow-band noise and sinusoids on the two processes were examined using a forward-masking paradigm. Within individual listeners, cubic difference bands (CDBs) behaved much like CDTs whereas the suppression effects produced by narrow-band noise were substantially less than those produced by sinusoids. These results suggest that at least partially different processes underlie the two phenomena. Second, the role of suppression in the difference between forward- and simultaneous-masking estimates of CDB amplitude was investigated. The data across listeners were highly variable but indicated a more complicated interpretation than that proposed by Shannon and Houtgast [J. Acoust. Soc. Am. 68, 825–829 (1980)].