bluuebunny/crossref_metadata_2025 huggingface dataset:
B-duration impulse definition: Some interesting results
Authors: Hynson K. , Hamernik R. P. , Henderson D.
Published: October 2005

Impulse noise is arbitrarily described as either an A or B duration impulse: (1) an “A” type is a free-field impulse where there is no reverberation component and the “A” refers to the duration of the maximum overpressure. (2) A “B”-type impulse is either an inherently reverberant impulse or an A-type impulse in an acoustically hard environment. The B-duration is, by definition, the impulse duration to a point on the total wave envelope 10 or 20 dB down from the peak. Two groups of chinchilla were exposed to 40-μsec A-duration impulses with a peak PLS of 158 dB. The first group of animals suffered minor TTSmax of about 20 dB at 4 kHz and virtually no PTS or hair cell loss. The second group of animals had large values of TTS (65–70 dB TTSmax at 4 kHz) that resolved to a 25 dB PTS at 4 kHz with concommitant severe cochlear lesions. The increased trauma suffered by the second group is apparently the result of the accidental addition of a reflected wave component that trailed the A-duration impulse. The reflected wave was 10–20 dB down from the initial peak and, therefore, might be discounted by the existing damage risk criteria or by using the B-duration measurement scheme. However, the data do suggest a temporal interaction between these two relatively innocuous impulses that is not accounted for within the present framework of the A- and B-duration concepts. Ultimately, these fortuitous results can be important in showing the necessity of specifying the total waveform when describing an impulse noise.
Propagation of sound at high intensities in a cylindrical duct with finite wall impedance
Authors: McDaniel O. H. , Reethof G.
Published: October 2005

High intensity acoustic wave propagation has been studied in a 12-in.-diameter anechoically terminated cylindrical duct. Sound pressure levels up to 175 dB were generated over a frequency range of 300 to 1000 Hz. Several absorptive liner sections were installed in the duct and the sound field was measured at stations upstream of the liner, within the liner, and downstream of the liner. Both plane waves and the first higher order “spinning” mode were generated. Harmonic spectra, waveform photographs, and mode shapes at the three measurement stations will be presented and the alteration of the finite amplitude effect due to the presence of the liner and liner nonlinearity will be discussed.
An integral-equation numerical solution for the acoustical vibrations in an axisymmetric cavity of arbitrary cross section
Authors: Henkel D. J. , Sobel L. H.
Published: October 2005

This paper investigates the natural acoustical vibrations in an axisymmetric cavity of arbitrary cross section. As the response must be spatially harmonic in the circumferential direction, the problem is governed by the two-dimensional wave equation for the motion in the plane of the cross section of the cavity. The problem is further reduced by one dimension through the use of an integral-equation representation of the wave equation. The resulting singular integral equation is solved numerically for the displacements at prescribed nodal points on the boundary. This approach is very economical in comparison with a numerical solution of the two-dimensional wave equation (for example, by means of the finite difference or finite element method), which requires the use of an area mesh. Furthermore, effects of a flexible cavity wall on the natural vibrations are easily accounted for in such an approach. A computer program was written for the case of a cavity of arbitrary cross section and numerical results are presented for the case of rigid cavity walls. To check these results, comparison was made with known Bessel solutions for a rectangular cavity and good correlations were found. To illustrate the general capability developed herein, numerical results are also presented for an “L” shaped cavity.
The acoustic near-field of a circular piston via impulse response techniques
Authors: Stepanishen P. R.
Published: October 2005

It has been recently shown by the author [J. Acoust. Soc. Am. 49, 1628–1639 (1971)] that the acoustic near- and far-field of a piston of arbitrary shape can be readily investigated using the impulse response technique. In the present paper, the acoustic near-field of a circular piston which is vibrating with a harmonic motion is investigated using the impulse response technique. Although the pressure at any spatial point in the near-field can be simply expressed as the Fourier transform of the spatially dependent impulse response of the piston, the integral is not readily evaluated in closed form. However, an asymptotic evaluation of the integral is readily performed and leads to a very simple representation for the acoustic near-field. The general characteristics of the undulatory near-field are immediately obvious from the solution which is shown to be in agreement with the asymptotic properties of known near-field results.
Model for the acoustical impedance of fibrous material facing resonators
Authors: Tseo G. G.
Published: October 2005

A simple model for the impedance of fibrous material facing resonator is formed. By a waveguide approach, the reactance is modeled as a length addition to the resonator cavity depth. The resistance is modeled as a function of oscillatory velocity based on flow resistance at static condition. The waveguide model is compared with a conventional lumped parameter model to fit the measured impedances using least-square approach. The waveguide model is shown to match closely with the measured data from fibrous materials of Feltmetal and Brunsmet.
Self-sustained musical oscillators
Authors: Schumacher R. T.
Published: October 2005

Most musically interesting oscillators consist of two systems, at least one of which is linear, coupled by a nonlinear force. Steady state oscillations of all such systems can be described by coupled nonlinear integral equations of the Hammerstein type, in which the kernels are determined by the impedances or admittances of the linear systems [R. T. Schumacher (to be published)]. Instruments may be classified as weakly nonlinear (woodwinds and brass played softly) or strongly nonlinear (bowed strings or beating reeds). Methods of solution differ strikingly in the two cases. In the former the reduction of the integral equations to a set of nonlinear algebraic equations to be solved numerically can be accomplished with the aid of computer programs for symbolic and algebraic manipulation. In the strongly nonlinear case, a generalization of Newton's method for a special model of a violin bow and a realistic string model has been successfully applied [R. T. Schumacher, op cit.] More generally useful and less expensive techniques depend on finding a suitable complete set of orthonormal functions for on-off processes (slip-stick or beating reed) and application of appropriate finite element methods of solution. Examples of solutions are given for chosen systems. [Work supported by NSF.]
Further study of violin free-plate resonances
Authors: Hutchins Carleen M.
Published: October 2005

For some time it has been apparent that the finding reported previously—namely, that a good sounding instrument of the violin family results when the “tap tone” frequency of the free back plate is a semitone to a tone higher than that of the free top plate—is not the only criterion to be respected in the optimum tuning of violin plates. Ten conventional violas were constructed using mode No. 5, the tap tone of free top and back plates, to determine whether frequency or so-called damping of this mode in the two plates is the more important for good tone production in the finished instrument. Findings will be discussed and illustrated with Chladni patterns and frequency amplitude curves—and compared to comments of professional violists on the tone and playing qualities of the 10 finished violas.
Measurement of damping in polymer materials
Authors: Plunkett Robert
Published: October 2005

Damping materials dissipate mechanical energy when cyclically strained by converting it to heat. For sinusoidal strain the amount of energy dissipated per cycle depends on temperature, frequency, and amplitude. Each of these should be measured and reported. If the energy dissipated is proportional to the square of the amplitude, the damping mechanism is called linear and the damping may be reported as energy per cycle loss as a function of amplitude, storage, and loss modulus, or storage modulus and loss ratio. The measurement of system energy loss may be made by direct measurement of force, deflection, and the phase angle between them. The energy loss may also be inferred from the rate of decay in free vibration, the electrical impedance of or the energy input to a vibrating electromechanical system of which the specimen is a part. Regardless of the method used, it is impossible to distinguish between the energy dissipation in the specimen and that dissipated elsewhere in the system. This latter must either be accurately known or negligibly small. In order properly to interpret the data, the state and distribution of strain must be known though the volume of the specimen. Methods for measuring and controlling each of these parameters will be discussed and illustrated.
Shear dampers for deflections of microinch magnitudes
Authors: Miller David , Otth David
Published: October 2005

Planetary spacecraft used for outer planet missions within our solar system, like the Mariner Jupiter/Saturn '77 (MJS77) Spacecraft, characteristically utilize either extremely long boom appendages to support science instruments sensitive to close spacecraft proximity or shorter booms that support heavy loads such as Radioisotope Thermaelectric Generators (RTG's). Common to both configurations are the small magnitude inertia effects (perturbances) that extended length or heavy boom weight might have on resulting spacecraft settling times important to clear TV picture generation by the video subsystem. For the MJS77 Spacecraft the rotation of the TV camera into a given position generates long settling times caused by the undampened perturbances of the 13-m magnetometer and heavy RTG booms. A series of modal analyses provided the necessary frequency and damping constraints for each boom to obtain short settling times. To ensure clear TV pictures 4% damping was required at very small displacements (ranging from 0.001 to 0.00005-in. deflections) and at low frequencies (1.8–0.2 Hz). The solution incorporated elastomeric shear dampers which had high loss tangent values in the frequency and temperature range expected at the base of each boom. The shear dampers were sized to ensure adequate strain and provide the desired boom stiffnesses. Presented are the shear damper design, results of full scale horizontal boom tests, and data on the effects of damper sizing, operating temperature, life cycle (fatigue) on boom frequency and damping. Instrumentation and method of boom exitation used for the full scale tests are also presented.
Noise-level units and objective and subjective sleep quality
Authors: Lukas Jerome S.
Published: October 2005

Studies of the effects of noise on sleep have varied widely with respect to noise sources, presentation and measurement techniques, age and sex of subject, and type of response data collected. There is little cause to wonder, therefore, why the results may appear inconsistent. This paper summarizes a review of research literature on sleep and noise. It suggests that the results obtained in various laboratories are reasonably consistent if the noise unit (or descriptor) accounts for the noise spectrum and duration and if the response measure accounts for induced changes in sleep stage, arousals, and behavioral awakenings. It also proposes a technique (Composite Sleep Quality) for estimating the degree of subjective sleep disturbance and shows the relationship of this measure to several methods for calculating total nighttime exposure.
Perception of vowel features in temporally segmented bursts of stop-consonant CV's
Authors: Tekieli Mary Ellen , Cullinan Walter L.
Published: October 2005

Segments of the burst portions of stop-consonant CV's, increasing in duration in 10-msec steps from the burst onset, were identified by 18 listeners. The responses were analyzed for the correct identification of vowel features. Coarticulatory effects of the vowel on the burst were found to (1) occur early in the burst, (2) vary with consonant and vowel, and (3) vary with vowel feature. In general, however, front versus back tongue placement for the vowel was perceived correctly most often, tongue height next most often, and the tense versus lax feature least often. For some CV's, sufficient cues for above chance level of identification of a feature were contained during the shortest segments of the burst. The results lend support to the point of view, in the case of unvoiced stops, that listeners can narrow the choice of the following vowel to a small number of alternatives prior to the beginning of the formant transitions or voicing.
Perceptibility of certain phonetic features in ongoing speech
Authors: Cole R. A. , Jakimik J.
Published: October 2005

There has been a great deal of research on the cues for phonemes in isolated syllables, but relatively little research has been performed on the perceptibility of different phonetic features in ongoing speech. In order to investigate this problem we developed a “listening for mispronunciation” (LM) paradigm. In the LM paradigm, subjects are presented with a prose passage in which various words are mispronounced. Subjects are instructed to press a response key as quickly as possible whenever they detect a mispronunciation. Since mispronunciations can be produced by varying a single phonetic feature in a word, the LM paradigm provides a technique for determining the relative perceptibility of different phonetic features. In the first experiment we compared the relative perceptibility of voicing and place of articulation for word-initial-stop consonants. Two versions of a short story were recorded. Words changed by the voicing feature in one version of the story (e.g., BOY to POY) were changed by place of articulation in the other version (e.g., BOY to DOY). Since the same word was changed in both versions, all contextual influences were held constant. The results showed significant differences in both the speed and accuracy with which listeners detected changes in voicing and place of articulation. In addition, a number of interesting asymmetries were observed, e.g., a change from [b] to [p] was not equivalent to a change from [p] to [b].
Influence of tempo on the closure interval cue to the voicing and place of intervocalic stops
Authors: Port Robert
Published: October 2005

The silent closure interval (CI) of medial stops is known to effectively cue their phonological voicing, so that ruby converts to rupee by splicing in a longer and silent CI [L. Lisker, Language 33, 42–49 (1957)]. In addition, Dorman et al. [J. Acoust. Soc. Am. 57, Suppl. No. 1, S48(A) (1975)] demonstrated that a short enough CI for synthetic double medial stops like -bd- will produce perception of a simple flapped -d-, overriding the F2 cue for a labial implosion. We investigated the sensitivity to speaking tempo of both these effects. By varying the silent CI of the medial stop in rabid from 10 to 120 msec, a continuum of 12 words was created, from ratted to rabid to rapid. Embedded in Fast and Slow carrier sentences and identified by 16 Ss, the Slow /b-p/ boundary at 75 msec shortened about 10 msec in the Fast condition. The Slow /b/-flap boundary at 35 msec shifted only 3 msec in the Fast condition. These results (1) replicate the Dorman et al. effect with natural speech even with labial cues on both implosion and explosion, (2) show that CI as a voicing cue is sensitive to speaking tempo, and (3) suggest that the boundary at which CI overrides other place cues is less sensitive to tempo.
Analysis of narrow-band noise and long-range transmission fluctuations at 406 Hz
Authors: Rosenberg Benjamin
Published: October 2005

Ten days of signal data from a fixed source off Eleuthera operating at a frequency of 406 Hz was recorded and analyzed at two receiver sites, one off Bermuda at a distance in excess of 1100 km, and the other at an intermediate distance. The signal envelope expressed in decibels was compared with several distributions which have been obtained theoretically and experimentally. It was found that the model for long-range propagation fluctuations derived by Dyer is a considerably better fit than the normal distribution. In addition, synoptic environmental data were used to obtain the multipaths to the intermediate hydrophone and an approximate computation carried out in order to obtain the distribution. It was found to be somewhat better than the Dyer model in both fit and estimate of the standard deviation. Ten days of narrow-band noise received at the Bermuda hydrophone was analyzed. The data were obtained during a period for which there were no sudden excursions that might be due to nearby shipping, and hence could be presumed to be surface generated at this frequency. The runs test for stationarity could be satisfied when the variance was used as the test parameter. The Rayleigh distribution was derived for surface-generated noise and when log transformed was shown to fit the experimental data quite well.
Intensity characteristics of auditory-nerve fibers: A preliminary analysis
Authors: Zwislocki J. J.
Published: October 2005

Currently available recordings indicate that spike rates in single auditory-nerve fibers increase with tone intensity according to S-shaped functions. In a given fiber, the spike rate tends to increase more rapidly below CF than above it without a systematic change in saturation rate. The shape of the rate-intensity functions varies from fiber to fiber. These relationships are explained in terms of a model of interaction between the cochlear inner and outer hair cells, in which the inner hair cells are assumed to produce excitatory and the outer cells inhibitory inputs to the radial fibers. The intensity characteristics of all hair cells are assumed to have essentially the same shape. The model explains also why it is difficult to detect net inhibition of spontaneous activity in the auditory nerve.
Syllables as concatenated demisyllables and affixes
Authors: Fujimura O.
Published: October 2005

A method is proposed to decompose English syllables into phonetically and phonotactically well motivated units, so that the complete inventory for segmental concatenation will contain at most 1000 entries and still reproduce natural allphonic variations. A syllable is decomposed into a syllable core and syllable affix(es). Syllable cores have a general form of (Ci) (Ci)V(Cf) (Cf), where V is a single vowel, and Ci and Cf are consonantal elements where Cf may be a glide (semivowel or vowel elongation). The /sp/, /st/, and /sk/ are treated as simple consonantal elements with a place specification, and the ordering of the elements within the core is strictly governed by the vowel affinity principle [Fujimura, IEEE Trans. ASSP-23, 82–87 (1975)]. The syllable core is divided into initial and final halves—demisyllables each of which can contain only one specification of the place of articulation. The final consonantal elements (such as /s/ in /tæks/) that follow a place-specified true consonant (/k/ in this case) are treated as syllable affixes. These affixes are all apical, and they observe voicing assimilation with respect to the true consonant in the core.
Space-time measurement of oceanic motions from a range-gated Doppler sonar
Authors: Pinkel R. , Spiess F. N.
Published: October 2005

A narrow-beam, 90-kHz Doppler sonar is being developed for the measurement of currents in the upper ocean. Transmitted sound is back scattered by the plankton and/or density structure in the sea. The Doppler shift of the return is proportional to the long-beam component of the drift velocity of the scatterers. Remote sensing of oceanic motions in this manner offers several advantages to the oceanographer. In particular, flow-speed information is available over great ranges. Kilometer-scale features in the sea can be monitored without recourse to expensive moored arrays of mechanical current meters. Prelimimary tests of an 87.5-kHz system were conducted from the Research Platform FLIP during May 1975. Using 100-msec simple pulses, the signal/noise ratio was favorable out to a range of ∼400 m. Comparisons between spectra of the remotely measured currents and those from a conventional current meter are encouraging. The system is currently being modified to permit transmission of frequency encoded signals. In this manner it is hoped to increase the useful range of the system to ∼1 km while improving resolution to ∼10 m.
Dichotic vs monotic masking functions may reveal central organization for speech identification
Authors: Berlin C. I. , Berlin H. L. , Hughes L. , Dermody P.
Published: October 2005

Previous studies of dichotic interference of speech by nonspeech challenges have presented targets and challenges at equal intensities In this study targets (CV stops) were first paired monotically with challenges (noise, vowel, sweeps, bleats and CV's) with the target held constant at 70 dB SPL and the challenges varied in intensity. Masking functions of the challenges on the targets were then generated. The dichotic presentations of the challenges vs the targets were then arranged at two levels: (1) that point at which the challenge masked the target to between 62% and 65% and (2) that point at which the challenge masked the target completely (less than chance). Using these monotic masking functions as references we asked subjects to listen only for the targets presented to one ear while the challenges were presented to the other ear. Dichotic interference functions revealed that, despite uniform monotic masking capabilities, the challenges were quite different in their dichotic effects. Bleats and CV's generated the greatest interference dichotically; sweeps generated some interference but, in contrast to bleats and CV's, did not generate a right ear advantage. The implication of these results will be discussed with respect to central organization for speech detection. [Support by NS-11647.]
Some laboratory topics in vibrations
Authors: Clausen William E.
Published: October 2005

Six topics are presented in a laboratory course in vibrations for advanced undergraduate and beginning graduate students. The concepts of moving coil transduction, resonance, damping, and multiple degree of freedom modelling are demonstrated in an experiment employing a mass-loaded cantilever beam. Clamped circular and rectangular plates are used to illustrate modal patterns, and the jump phenomenon associated with a nonlinear hard-spring system is observed when the circular plate is strongly excited. Impact and the transmission and reflection of longitudinal waves in rods are the subjects of a spring-gun and rod experiment. The students conduct a qualification test of the type used to verify that electrical equipment to be installed in nuclear power generating stations can withstand typical earthquakes. Another qualification test employs a drop table and a half-sine pulse test. Longitudinal vibrations of concrete test specimens are used in a resonance experiment to compare stiffness and damping of different concrete mixes.
Multivariate adaptive testing applied to the prescriptive fitting of hearing aids
Authors: Levitt H. , White R. E. C. , Resnick S. B.
Published: October 2005

Among the problems encountered in fitting of hearing aids are (i) measurements of performance are subject to significant random fluctuations; (ii) subjects typically adapt to the hearing aid resulting in gradual drifts in the optimum parameter values; (iii) variables interact, thereby presenting certain dangers if only one variable is manipulated at a time; and (iv) data obtained under carefully controlled conditions do not always correspond to performance in the field. The simplicial method [G. E. P. Box, Appl. Statist. 6, 81–101 (1957)] is a powerful adaptive technique designed for problems of this type and has been used as part of an ongoing study to develop a practical protocol for the prescriptive fitting of a wearable master hearing aid. Preliminary trials with five subjects showed superior performance for the fitted wearable master hearing aid than that obtained with the subjects' own aid under comparable conditions of speech in noise. [Research supported by PHS-Contract No. NIH-N01-NS-4-2323.]
Sequential voice effects in dichotic CV indentification
Authors: Paul D. J.
Published: October 2005

Previous work suggested that (i) interaural differences in F0 constitute a more effective voice parameter than vocal tract length (VTL) in reducing wrong-ear intrusions when voice varies on the unattended ear only and (ii) VTL is more effective when only attended ear voice varies. Here /bE, dE, b3, d3/ identifications were measured with full permutation of both attended and unattended ear voice parameters and their first order sequences. Overall results were similar to (ii) and suggested that higher level processing is evoked by attended variation in VTL. The short vocal tract (SVT), having F1, F2, and F3, produced many consonant intrusions when on the unattended ear. This was an absolute property of SVT rather than of a switch from long vocal tract (LVT) to SVT as such. LVT on the unattended ear caused more errors than SVT did, but these were not located on vowels and intrusions. Absence of a switching effect for LVT also in the task argues against any task-independent intrusiveness of a novel voice.
Effect of acoustic variation in stimuli on response patterns in dichotic listening
Authors: Carney Edward , Speaks Charles
Published: October 2005

Two sets of tapes for dichotic listening were prepared from synthetic stop-vowel stimuli which varied on a voice-onset-time (VOT) continuum. Each set contained the same three voiced syllables (ba, da, ga) in combination with one of two sets of voiceless stimuli which differed in VOT by 30 msec from Set I to Set II. The two sets of voiceless stimuli differed only in acoustic structure, not in the listeners' identification. Six stimulus-onset asynchronies (SOA) were used for each of four listeners who demonstrated right-ear advantages. Set I results differed from Set II results in the SOA at which the left-ear score surpassed the right-ear score when the left-ear signal was lagged. Results are discussed with reference to a “phonetic processing” hypothesis [Berlin et al., J. Acoust. Soc. Am. 53, 699–709 (1973) and Studdert-Kennedy et al., J. Acoust. Soc. Am. 48, 599–602 (1970)] and to an “acoustic interference” hypothesis [Speaks et al., J. Acoust. Soc. Am. 57, S52 (A) (1975)]. [Supported by USPHS Grant No. NS-12125.]
Optimal octaves vs formant frequencies
Authors: Miner R. , Danhauer J. L.
Published: October 2005

The vowels /i/, /a/, and /u/ were recorded by a general American speaker and then band-pass-filtered through eight different bandwidths from 80 to 20 000 Hz. The recorded filtered vowels were presented to two groups of subjects to determine which bandwidths contributed most to their perception (similarity ratings) and identification (direct estimation) of the vowels. These bandwidths were then compared to the measured formant frequencies of the vowels and to the optimal octaves fro these vowels reported in the literature. Results revealed that there was a specific bandwidth which allowed correct perception and identification of each vowel, and the bandwidths were compatible to the reported optimal octaves. Furthermore, these bandwidths coincided with the different formant frequencies respective to the vowels.
Acoustic analysis of low vowels in the Boston dialect
Authors: Laferriere M.
Published: October 2005

A spectrographic and computer-aided analysis was made of the low vowels [æ] (cat), [a] (cart), and [§] (caught, cot) of a speaker of Boston English. In this dialect, [æ] has higher F2 values than [a] and [§], [a] and [§] share the same F2 range but have different F1 values:

[æ] [a] [§]

F1 range 465–650 670–770 465–635

F2 range 1440–1745 1250–1425 1135–1410

[a] and [§] are thus equally backed (same F2) in relation to [æ]. [a] and [§] are distinguished from each other by tongue height (F1) and lip-rounding rather than by distance of tongue constriction from the glottis (F2). The Boston data thus provide counterevidence to the traditional [Principles of the IPA, 5–6 (1949)] claim that [æ] and [a] are front vowels and [§] a back vowel. Further, the data support a three-way distinction among low vowels: [æ]-front, [a]-back unrounded, and [§]-back rounded.
Measurement error for vowel durations
Authors: Allen George D.
Published: October 2005

In recent studies involving the correlation of speech segment durations, the measurement error in locating segment boundaries has usually been ignored or assumed to be constant and small. Since the relative magnitude of the error in locating such a boundary can have a profound effect on derived intersegment correlations, an experiment was designed to estimate these errors directly. Several tokens of four sentences containing syllables differing in the quality, length, degree of stress, and consonantal context of their nuclear vowels were copied onto two-track tapes and sent to several professional phoneticians with instructions to measure the durations of the indicated vowels, on first one track and then, at least two weeks later, the other. The resulting measurement errors varied systematically in several ways: (1) long, stressed vowels had greater errors than short, unstressed ones; (2) initial voices stops (/b/0 were easiest to segment and approximants (/w/) hardest, with voiceless stops (/k/) and fricatives (/f/) intermediate; (3) great differences among phoneticians appeared to depend on the segmentation criteria used, not their instrumentation.
Impact of modern acoustic technology on the scientific assessment of marine life
Authors: Holliday D. V.
Published: October 2005

In recent years significant advances have been made in understanding the effects of the marine environment on the propagation and scattering of sound and in acoustic signal processing. A few of these developments have been used in the study of marine life. Several examples of the uses of underwater acoustics to study life in the sea are examined. Specific topics include studies of plankton and small nekton; investigations and assessments of commercial fish stocks; and studies of marine mammals.
Quantitative measurements of scattering from tissues
Authors: Reid J. M.
Published: October 2005

The extraction of quantitative information on the scattering process sufficient to determine the scattering mechanism and to characterize tissues is a difficult problem which has been attacked from many viewpoints. Heterogeneous biological tissues require focused beams and short pulses to isolate waves scattered from particular structures. Analysis must be done over wide bandwidths and in field regions where analytic expressions are not available. Another complication is the frequency-dependent absorption in both overlying tissues and in the tissue being measured. Five levels of scattering measurement have been identified. The first is the simple measurement of a scattered wave by reference to an external standard. The other levels require corrections for (1) overlying tissue absorption; (2) wave and field-shape interactions with the measuring equipment; (3) sample-tissue absorption; and (4) the effect of concentration to determine the per-cell or structure scattering cross section. Measurements of redcell scattering illustrate that these methods are practical. The scattering cross-section magnitude and angular and frequency dependence correlate with theory for scattering from compressible viscous spheres. Because the substitution methods outlined can correct for the interaction between equipment parameters and wave-shape effects, a promising area appears to be the development of substitution standards for in vitro and in vivo measurements.
Experimental determination of low-wave-number components of turbulent boundary-layer wall-pressure fluctuations
Authors: Leehey P. , Martin N. C.
Published: October 2005

Two rectangular plates with different edge conditions and a rectangular membrane were characterized experimentally as spatial filters and then used to measure the low-wave-number components of wall-pressure fluctuations under a turbulent boundary layer. Measurements were made in a test section wall of a low-turbulence subsonic wind tunnel. Special quieting measures were taken to reduce acoustic contamination of the data. Corrections for acoustic contamination of at most 2 dB were required for some measurements. Some correction was also required for convective ridge contamination with two of the three spatial filters. Data was obtained for momentum thickness Reynold's number from 5000 to 10 000 for a smooth wall at zero-mean-pressure gradient. The filters were centered on zero lateral wave number and, for fixed reduced frequencies, covered a range of streamwise wave numbers from 8% to 25% of the corresponding convective ridge wave number. Typical low-wave-number spectrum levels were about 35 dB below the corresponding convective ridge levels. [Work supported by the Sonar Technology Division, Naval Sea Systems Command and the Sensor Technology Program, ONR.]
Noise model for slow-speed trucks on Baltimore city streets
Authors: Prahl F. A.
Published: October 2005

The following list outlines the essential elements in the development of a noise model for slow-speed trucks in Baltimore, MD. (1) Measurements were made of peak passby-noise levels and average running speeds of trucks operating on the streets of Baltimore. The noise measurement system was the General Radio Type 1981 sound level meter, with a 50-dB dynamic range and a maximum hold capability. We also included a counting program to classify a clearly defined segment of Baltimore's truck population into one of three categories: heavy trucks (vehicles with more than 2 axles), medium trucks (vehicles with 2 axles and 6 wheels), and buses (both city and interstate). (2) Synthesize data and develop linear regression equations for the emission level (peak passby level at 50 ft) of slow-speed heavy and medium trucks as functions of average running speed. (3) Substitute the empirical emission levels into the Transportation Systems Center computer model for the prediction of L10 (dBA) due to road traffic. The final emission level (EL) equation for heavy trucks is EL = 83.4 − 2.5 log S; for medium trucks the equation is EL = 67.4 + 5.2 log S. In both equations S is average running speed in miles per hour and 14 < S < 30. In both vehicle categories, correlation between emission level and average running speed is very low; in fact, statistical tests indicate that the correlation coefficients do not differ significantly from zero. However, we are constrained to use equations which relate emission levels to average running speed because individual truck speeds cannot be predicted for future years. [Work supported by the Interstate Division for Baltimore City.]
Auditory analog to the Craik-O'Brien-Cornsweet illusion in vision
Authors: Jesteadt Walt , Green David M. , Wier Craig C.
Published: October 2005

We have generated an auditory loudness illusion by amplitude modulating either a noise or a sinusoid using a temporal pattern analogous to the spatial luminance patterns used by Craik, O'Brien, and Cornsweet. The stimulus is gated on at a constant amplitude for some foreperiod, then, for example, the intensity is slowly decreased over a 100-msec interval by 10 dB, then rapidly increased by 20 dB, then slowly decreased again to the initial amplitude where it remains for an interval equal to the foreperiod. Subjects adjusted the intensities of two square-gated stimuli to match the loudnesses of the segments of the modulated stimulus before and after modulation. The results indicate that the stimulus following the modulation sounds 3 to 6 dB more intense than the stimulus preceding the modulation, when in fact the intensities are equal. Reversing the modulation reverses the direction of the effect. We will present examples and discuss the frequency, intensity, and temporal parameters that influence the magnitude of the illusion. [Supported by the NIH.]
Effects of human middle-ear muscle contractions on speech intelligibility
Authors: Cox L. C. , Greenberg Herbert J.
Published: October 2005

The present study was designed to further assess the relationship between the acoustic reflex and speech intelligibility. Monosyllabic words mixed with noise were presented to 35 subjects at −6, −3, 0, and +3 dB S/N ratios. The word lists were presented with a 2000-Hz tone in the contralateral ear at a level either 15 dB above or 20 dB below the acoustic reflex threshold. This was performed to evaluate the intelligibility of the monosyllabic words with the acoustic reflex contracted or relaxed. The results indicated that at S/N ratios of −3 and 0 dB a significant decrement in speech intelligibility occurred. A slight but not significant decrement was seen at −6 and +3 dB S/N. The results of the present study show that contraction of the acoustic reflex causes a decrease in speech intelligibility. These results are discussed along with possible reasons to explain the lack of agreement with previous research.
Lip and jaw coordination during the production of /f, v/ in English
Authors: Hasegawa A. , McCutdheon M. J. , Wolf M. B. , Fletcher S. G.
Published: October 2005

The major articulatory constriction for the fricative consonants /f, v/ in English is established by the contact of the maxillary incisors and the lower lip. The constriction is formed by the movements of the lower lip and the mandible. Experiments were conducted to examine lip and jaw movements during the production of /f, v/ in VCV Contexts (V = /i, ε, æ, ɑ, o, u/). Reflectors (<1.5 mm in diameter) were placed on the subject's lips and on rigid wires attached to the jaw and head. Reflector displacements on the midsagittal plane together with voice and upper-teeth-lower-lip contact information were digitized and recorded every 10 msec. The locations of the reflectors with respect to the maxillary incisors were analyzed after correcting for head movements. Preliminary analysis indicated differences in lip and jaw displacement as a function of (1) phonetic context and (2) speaking rate. Results will be contrasted with findings by other investigators for bilabial stops. [Supported by NIH Grant NS-11852-01A from NINDCDS.]
What can computer-synthesized speech tell us about the language comprehension impairment of adults with residual dysphasia?
Authors: Tallal Paula , Newcombe Freda
Published: October 2005

Men with chronic, focal brain-wounds were examined for their ability to discriminate (1) nonverbal complex tones, (2) computer-synthesized steady state vowels, (3) computer-synthesized stop-consonant-vowel syllables with 40-msec duration formant transitions, and (4) synthesized stop-consonant-vowel syllables with 80-msec-duration formant transitions. Subjects with a language comprehension deficit (as measured by the token test) were selectively impaired in their ability to respond correctly to rapidly changing acoustic stimuli, regardless of whether they were verbal or nonverbal. Subject's degree of perceptual impairment was highly correlated with their degree of language comprehension impairment. These adult dysphasics pattern of impairment on these perceptual tests is similar to that found in children with developmental dysphasia [P. Tallal and M. F. Piercy, Neuropsychologia 11, 389–398 (1973); 12, 83–93 (1974); 13, 69–74 (1975)]. [We are grateful to the Grant Foundation of New York and the Medical Research Council of Great Britain for supporting this research.]
Relationship between pitch deviancy and intelligibility of deaf children's speech
Authors: McGarr Nancy S. , Osberger Mary Joe , Gold Toni
Published: October 2005

This study was designed to investigate the relationship between pitch deviancy and intelligibility of deaf children's speech. Ratings of pitch and overall intelligibility of the children's spontaneous speech were obtained from three listeners familiar with the speech of the deaf. The rating scales used were from the Communication Profile developed at the National Technical Institute for the Deaf (D. Johnson, Proceedings of the Institute on Rehabilitative Audiology, July 1974). Preliminary results suggest that speech intelligibility and pitch deviancy are not significantly correlated. The relationship between rate d pitch deviancy and deviance of the fundamental frequency as measured by spectrographic analysis will be discussed. Analysis of the interaction between pitch deviancy, speech intelligibility, and hearing level will also be presented. [Research supported by the New York State Education Department: CREED Project ED-73-001 DC.]
Normal and reduced phonological space in the production of vowels by deaf adolescents
Authors: Monsen R. B.
Published: October 2005

The production of the vowels /i/,/a/,/c/, and the diphthong /ai/ was investigated spectrographically in the speech of 36 deaf and 4 normally hearing adolescents. The phonological space defined by the maximum and minimum values of F1 and F2 is found to be reduced for many of the deaf subjects. This reduction of phonological space is due primarily to a restricted range of F2 and secondarily to a restricted range of F1. The degree of F2 variation bears a significant positive correlation (0.76) to the intelligibility of the subjects' connected speech. It is suggested that the phonological space reduced most noticeably in the dimension of the second formant is due to the abnormal auditory and visual feedback imposed upon the deaf child: the deaf child's frequency sensitivity is typically worse in the region of the second rather than the first formant; the articulatory gestures of tongue movement, which exert a strong influence on the movement of the second formant, are among the most difficult for the deaf child to see. [Supported by NINCDS Grant 03856.]
Some properties of formant frequencies of vowels uttered by hearing-impaired children
Authors: Hiki S. , Kagami R.
Published: October 2005

First and second formant frequencies (F1, F2) of the five Japanese vowels /i, e, a, o, u/ in isolated utterances by 35 hearing impaired children (aged 6 to 11) were measured utilizing sound spectrograph, and the results were compared with those of 8 normal children (aged 7 to 12). The distribution of each kind of vowel on the F1−F2 plane showed that the formant frequencies of the impaired children deviated significantly from the normal range especially in /i/ and /o/. The tendency of perceptual confusion regarding the kind of vowel corresponded well to the deviation of formant frequencies. The relation between the formant frequencies of the five Japanese vowels of each of the impaired children were classified on the F1−F2 plane into the following six types: F2 range reduced, F2 range reduced and rotated, /o/ and /a/ close together, /i/ and /e/ close together, neutralized, and F1 raised. Based on a muscle contraction model of speech organs, those differences between the normal children and the impaired children were explained in terms of the nature of imperfection in articulatory movement. Use of visual display of vowels on the F1−F2 plane for speech training of the hearing impaired children was also discussed.
Articulation functions for normal and hearing impaired subjects on the MRT and SSI tests in multitalker noise
Authors: Miner R. M. , Danhauer J. L.
Published: October 2005

Articulation functions were established for three groups using the Synthetic Sentence Identification (SSI) test and the Modified Rhyme Test (MRT) in three message competition ratios (MCR's) of multi-talker noise. Mean scores on the SSI and the MRT were obtained for 35 normally hearing and six flat sensorineural and six high-frequency sloping sensorineural hearing impaired subjects. An ANOVA revealed a significant difference between tests, groups, presenation conditions, and significant interactions between variables. SSI scores were not significantly different among the tested groups while the MRT scores were significantly different at two MCR conditions. Articulation functions were considered typical for each group tested. The results suggest that the SSI and MRT are two different tests, examining two separate areas of discrimination.
Perceptual features of normally hearing and hearing impaired subjects revisited
Authors: Lawarre R. M. , Danhauer J. L.
Published: October 2005

Perceptual strategies in rating dissimilarities among 24 prevocalic consonants paired with /a/ were investigated for normally hearing and two groups of hearing impaired subjects (i.e., one with flat, and one with sloping sensorineural losses). A 576-item equal appearing interval scaling data collection method was employed. The diadic-paired stimuli were presented bilaterally at MCL. Subjects' ratings on a 1–7 scale were converted to 24 × 24 full symmetric dissimilarity matrices and submitted to INDSCAL analysis. Individual group and combined analyses were performed. Results revealed features (e.g., sibilant, sonorant, and nasal) common to all groups, as well as group-specific features showing interactions among manner, place, and voicing categories. Results were compared to earlier investigations and data showed that subjects used features in their perception of the speech stimuli, that both common and group-specific features were used, and that individual differences in subjects' weightings of features were present.
Time harmonic acoustic radiation from a submerged elastic shell defined by nonconcentric circular cylinders
Authors: Shaw R. P.
Published: October 2005

A time harmonic pressure is applied to the interior of an elastic body bounded by nonconcentric circular cylinders and immersed in an acoustic fluid. The resulting acoustic radiation is determined as an expansion in the nonconcentricity distance, in the same manner as done earlier [R. P. Shaw and G. R. Tai, J. Acoust. Soc. Am. 56, 1437–1443 (1974)] for an acoustic body. Full equations of elasticity are used since the boundary integral equation method employed reduces these to the consideration of surfaces anyway as would be the case for shell theory. Again, nearest neighbor modes (j−1 and j+1) are introduced in the first order solution for a forcing internal pressure in the jth mode. [Work supported by Structural Mechanics Division, ONR.]
Validity of the parabolic equation
Authors: Palmer D. R.
Published: October 2005

Much of the discussion of the validity and the physical interpretation of the parabolic equation is borrowed from the literature on electromagnetic propagation in turbulent media and simply does not apply to acoustic propagation in the ocean. Here we start with the inhomogeneous Helmholtz equation characterized by a sound speed which depends on all three spatial coordinates and use standard techniques from scattering theory to develope the parabolic equation. We find two assumptions are required: a forward-scattering or eikonal approximation in the horizontal plane and a degenerate spectrum assumption. The degeneracy assumption is reflected in a stationary-phase approximation and is intimately related to the definition of the wavenumber ko. We derive improved equations by relaxing these assumptions. A weaker stationary-phase approximation reduces the dependence of the solution on the choice of ko and the forward-scattering approximation is relaxed by assuming the “supereikonal” approximation.