bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of the single woodwind tone hole
Authors: Keefe Douglas H.
Published: October 2005

A single tone hole may be generally represented in the transmission-line description of a woodwind musical instrument by a T-section circuit. This circuit element is comprised of a shunt and series impedance whose values differ depending on whether the hole is open or closed. The imaginary parts of these impedances have here been calculated as functions of frequency in terms of the main bore diameter, and the tone-hole chimney height and diameter. The loss-free wave equation is solved for a single tone hole placed through the wall of a cylindrical main bore. Green function expansions are made in both the main air column and tone hole. These two expansions must be equal on the surface of intersection between the main bore and tone hole, and this condition may be expressed by an integral equation over the surface. An approximate solution to the integral equation is obtained by Schwinger’s variational formulation, and the impedance parameters in the T section are thereby computed and displayed in a form for use by musical acousticians. The series impedance for both open and closed holes is a negative inertance. The shunt impedance of a closed hole is a compliance which is simply related to the closed-hole volume. The shunt impedance of an open hole is written in terms of the open-hole effective length and expressed as a function of the tone-hole proportions.
Psychoacoustic and phonetic temporal processing in normal and hearing-impaired listeners
Authors: Tyler Richard S. , Summerfield Quentin , Wood Elizabeth J. , Fernandes Mariano A.
Published: October 2005

Four measures of auditory temporal processing were obtained from 16 normals and 16 individuals with a hearing loss of heterogeneous origin. These measures were: (1) temporal integration—the difference in detection thresholds between signals of 10- and 1000-ms duration (which was determined to provide an estimate of the ability to integrate energy over time), (2) gap detection—the shortest duration of silence between two noise bursts that can be discriminated from an uninterrupted noise, (3) temporal difference limen—the increment in duration necessary to detect a difference in the duration of a noise burst, (4) gap difference limen—the increment in duration necessary to detect a difference in the duration of a silent interval between two noise bursts. Each measure was obtained for stimuli centered both at 500 and at 4000 Hz using a three-alternative forced-choice procedure. In addition, measures of identification and discrimination were obtained for two sets of synthetic speech syllables varying chiefly in a temporal parameter, voice-onset-time, from /ba/ to /pa/ and from /bi/ to /pi/. Finally, speech identification in noise was measured with the FAAF test. Most of the hearing-impaired listeners displayed poorer temporal analysis than the normals on all of the psychoacoustical tasks, regardless of whether the two groups were compared at similar sound pressure levels or at similar sensation levels. Although the hearing-impaired listeners displayed a reduction in the ability to discriminate subphonemic cues for the voiced–voiceless distinction, their identification of that distinction in stop consonants appeared to be normal. The hearing-impaired group made about twice as many errors as did the normals on each of the consonant features of place, manner, and voicing when identifying speech in noise. Increased temporal difference limen and longer gap-detection thresholds were found to correlate significantly with reduced speech intelligibility in noise, even when the effects of the pure-tone threshold loss were partialed out.
Temporal discrimination in the goldfish
Authors: Fay Richard R. , Passow Betty
Published: October 2005

The capacities of the goldfish to detect changes in sound burst repetition rate were studied using classical respiratory conditioning. In experiment I, the just detectable amount of an instantaneous random jitter of burst period was measured as a function of mean period. In experiment II, the just detectable amount of slow sinusoidal jitter of burst period was measured for three burst types having different spectral and waveform characteristics. In experiment III, sinusoidal jitter detection thresholds were measured in the presence of varying degrees of random jitter. The data show that (1) rms sinusoidal and random jitter in a periodic train of bursts are approximately equally detectable. (2) Sinusoidal jitter detection depends upon burst period duration and the short-term envelope definition and not upon frequency-domain information. (3) For a given burst period, stimulus jitter and an internal temporal noise appear to add independently to determine period discriminability. (4) Psychophysical estimates of internal temporal noise are 0.160 and 0.710 msec at periods of 5 and 10 msec, respectively. The data are consistent with the hypothesis that the burst period discrimination task is based upon a measurement of the time interval (duration) between spikes in auditory neurons.
Gap detection in normal and hearing-impaired listeners
Authors: Fitzgibbons Peter J. , Wightman Frederic L.
Published: October 2005

Temporal resolution, estimated by measuring the minimum detectable gap (Δt msec) separating two successive signals, was assessed in five normal-hearing and five cochlear-impaired listeners. The signals were octave-band noises (400–800 Hz, 800–1600 Hz, and 2000–4000 Hz) presented in a background of continuous, broadband notched noise that was applied to eliminate unwanted spectral cues. Temporal resolution in all listeners showed systematic improvement with an increase in octave-band center frequency. Resolution in the hearing-impaired subjects was significantly poorer than normal regardless of whether the comparisons were made at equal sound pressure level or at equal sensation level.
Sound transmission through windows I. Single and double glazing
Authors: Quirt J. D.
Published: October 2005

The results of an extensive series of laboratory measurements of sound transmission through windows are presented. By reference to these data, the systematic dependence of the sound transmission loss on glass thickness and interpane spacing is evaluated.
Diffraction constants for pressure gradient transducers
Authors: Woollett Ralph S.
Published: October 2005

Conventionally the diffraction constant D of a receiving transducer (microphone or hydrophone) is defined as the ratio of the average sound pressure acting on the blocked diaphragm to the free-field sound pressure. This definition is inadequate for transducers that have complex vibration patterns, and, in the absence of ad hoc modifications, it will fail to give the correct results for pressure gradient transducers. A new definition based on the general theory of transducers with fixed velocity distributions is therefore introduced. The diffraction constant is assigned not only the function of accounting for scattered wave effects but also the function of extracting from the surface pressure distribution the component that drives the velocity distribution (or vibration pattern) of the transducer. The diffraction constant depends on the choice of the reference velocity that is associated with the acoustic port of the transducer. A spatial rms reference velocity is defined, and it is shown to be a suitable reference for pressure gradient transducers. Calculation of the diffraction constant is carried out for the following piezoelectric pressure gradient hydrophones: a flexural disk supported inside an annular mass, an end supported flexural bar, a cantilever bar, an oscillating rigid cylinder, and an oscillating rigid sphere. The use of the diffraction constant in conjunction with the electroacoustic circuit of the hydrophone to calculate voltage receiving response is described, and the circuit information needed to illustrate the procedure is given for the flexural disk hydrophone.
Acoustic cues to final stop voicing for impaired- and normal-hearing listeners
Authors: Revoile S. , Pickett J. M. , Holden Lisa D. , Talkin David
Published: October 2005

Voicing perception for final stops was studied for impaired- and for normal-hearing listeners when cues in naturally spoken syllables were progressively neutralized. The syllables were ten different utterances of /dæp, dæk, dæt, dæb, dæg, dæd/ spoken in random order by a male. The cue modifications consisted progressively of neutralized vowel duration, equalized occlusion duration, burst deletion, murmur deletion, vowel-transition interchange, and transition deletion. The impaired subjects had moderate-to-severe lossses and showed at least 70% correct voicing for the unmodified syllables. For the voiced stops, vowel-duration adjustment and murmur deletion each resulted in significant reductions in voicing perception for more than one-third of the impaired listeners; all normals showed good performance following neutralization of these cues. For the voiceless stops, large percentages of both listener groups showed decreased voicing perception due to the burst deletion, though a majority of both groups performed well above chance even after the vowel-duration adjustment and the burst deletion. When the vowel off-going transitions were exchanged between cognate syllables in given pairs, the effect on voicing perception exhibited by many impaired- and all normal-hearing listeners implicated the vowel transitions as an important additional source of cues to final-stop voicing perception.
Detectability of time-varying interaural correlation in narrow-band noise stimuli
Authors: Grantham D. Wesley
Published: October 2005

In a two-interval, forced-choice task, observers discriminated a binaural noise whose interaural correlation r varied according to the function r(t) = m cos 2π fmt from an interaurally uncorrelated noise [NU; r(t) = 0.0]. The former stimulus produces a perceptual binaural ’’flutter,’’ where the flutter rate is equal to the modulation frequency fm, and the amount of flutter corresponds to m. The stimuli were 0.4-octave-wide Gaussian noises with center frequencies of 500, 1000, 2000, or 4000 Hz. Presentation levels were 70–75 dB SPL; duration was 1.0 s. For a given modulation frequency, the peak interaural correlation m was varied in a blocked procedure, and thresholds were estimated as that value of m required for 75% discriminability. Plotting thresholds as a function of fm yields a modulation function, which can be interpreted as an ’’attenuation characteristic’’ of the binaural system. For the 500-Hz stimulus, thresholds increased from m = 0.28 at fm = 1 Hz to m = 0.80 at fm = 50 Hz. For higher frequency stimuli, discrimination was generally poorer and the modulation functions were flatter: thus, for 2000 Hz, m = 0.54 at fm = 1 Hz and m = 0.71 at fm = 20 Hz; for 4000 Hz, m = 0.71 at fm = 1 Hz and m = 0.81 at fm = 10 Hz. The modulation function from an ’’ideal observer’’ (at 500 Hz) differed in both form and absolute level from those of real observers. The data are discussed in relation to previous work on dynamic binaural processing.
Effect of inlet/outlet locations on higher order modes in silencers
Authors: Eriksson L. J.
Published: October 2005

A series of insertion loss measurements was made using an impedance tube with a broadband noise generator and anechoic termination as well as a small, four-stroke, single cylinder gasoline engine on a variety of expansion chambers to determine the effect of inlet/outlet locations on higher order mode propagation. Higher order mode excitation was evaluated for a variety of chamber diameters, outlet offsets, combined inlet and outlet offsets, and inlet and outlet angular positions. For both sources the (0,1) first symmetric mode and (0,2) second symmetric mode appeared to be excited in chambers with inline inlet/outlet locations and an expansion ratio greater than about nine. The (0,1) mode could be eliminated when the outlet was positioned on the pressure nodal circle of the (0,1) mode. Offset of the inlet and outlet appeared to excite the (1,0) first asymmetric mode. This mode could be eliminated by rotating the inlet and outlet to an angular separation of 90°. This configuration appeared to excite the (2,0) second asymmetric mode.
Optimization techniques and inverse problems: Probing of acoustic impedance profiles in time domain
Authors: Lesselier D.
Published: October 2005

A method of acoustic probing of an inhomogeneous plane stratified medium is discussed. The impedance profile is reconstructed from a time-domain analysis of the pressure reflected when this medium is illuminated by a known pulse. This analysis is made from an exact integral formulation in an iterative manner by means of the optimization theory. At each step, the direct problem (scattered pressure computation) and its related adjoint problem are solved for a given impedance profile. The behavior of this probing procedure is examined particularly in comparison with known approximated techniques based on a deconvolution process.
Effects of gunfire on hearing level for selected individuals of the Inter-Industry Noise Study
Authors: Johnson Daniel L. , Riffle Carol
Published: October 2005

Using the information available from Inter-Industry Noise Study, the hearing levels of 68 pairs of workers, matched for sex, age, and exposure level, were evaluated. For each pair, one of the participants had indicated exposure to nonoccupational gunfire during the previous year. Differences in mean hearing levels between the male participants exposed to gunfire and those not exposed were clearly apparent and varied between 9 to 16 dB for the frequencies at 3000, 4000, and 6000 Hz. There were no significant differences in female hearing threshold levels. These changes in male hearing are equivalent to the effect of an occupational exposure of 89 dB for 20 years. However, the results do not indicate that there are any synergistic effects between gun exposures during a participants recreational time and noise exposure during his working hours.
Comments on ’’Elastic wave invariants for acoustic emission’’ [J. Acoust. Soc. Am. 70, 110–115 (1981)]
Authors: Weaver Richard
Published: October 2005

A symmetric radiation stress tensor is presented for elastodynamics.
Comments on ’’Sound propagation through an East Australian current eddy’’ [J. Acoust. Soc. Am. 63, 1381–1388 (1978)]
Authors: Hall Marshall
Published: October 2005

The normal-mode theoretical spectra of acoustic intensity, applicable to the experiment reported in the subject paper, are presented for horizontal ranges of around 14 km. The sound-speed profile contained both a surface duct and a submerged duct. For the cases of sound sources in both the surface duct and the submerged duct (and a receiver in the submerged duct), the experimental results are in fair agreement with the theory. Surface scattering and volume scattering cannot account for the differences that did occur, since estimates of the scattered intensities are no higher than the normal-mode prediction.
Interpreting the role of suppression in psychophysical tuning curves
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

We describe two models which make different assumptions about the factors determining threshold for psychophysical tuning curves (PTCs) determined in simultaneous masking. The models make different predictions about the amount of activity evoked by off-frequency maskers in the frequency region of the signal. The predictions were tested by using a forward-masking technique to estimate the amount of this activity. The data support a model which assumes that threshold in simultaneous masking corresponds to a ‘‘swamping’’ of the signal activity by that of the masker, rather than a suppression of the low-level signal to its absolute threshold. To explain the fact that PTCs in forward masking are sharper than those in simultaneous masking, the model requires that suppression acts to sharpen the excitation pattern of the masker. This sharpening is not seen in simultaneous masking, since suppression in a given frequency region affects both signal and masker.
Pure-tone pitch anomalies. I. Pitch-intensity effects and diplacusis in normal ears
Authors: Burns Edward M.
Published: October 2005

Pitch-intensity functions were obtained in both ears of five normal-hearing subjects, together with measurements of binaural diplacusis as a function of intensity. The results show that pitch-intensity functions are often significantly different in the two ears of a given subject at a given frequency. Furthermore, for each subject and frequency condition tested, an intensity existed for which no significant diplacusis was found. For these conditions, therefore, binaural diplacusis as a function of intensity could be accounted for by the interaural differences in pitch-intensity functions. Forward-masking patterns (FMP’s) as a function of intensity were also obtained in both ears of several subjects. The FMP’s were compared with pitch-intensity functions, obtained for the same conditions, for evidence of a covariation in the direction of shifts in masking patterns as a function of intensity with the direction of pitch shifts as a function of intensity. No convincing evidence of such a covariation was found. The implications of the results of these experiments are discussed relative to the question of temporal versus tonotopic coding of pure-tone pitch.
Pitch of unresolved, two-component complex tones
Authors: Feth Lawrence L. , O’Malley Honor , Ramsey Jw
Published: October 2005

Helmholtz [On the Sensations of Tone (Dover, New York, 1954), 2nd English edition] reported that the pitch of a two-component complex tone could be shifted slightly by increasing the amplitude of one component. The pitch was shifted toward the frequency of the more intense component. Helmholtz attributed the pitch shift to a variation in the instantaneous frequency of the two-tone complex. This laboratory has previously investigated the discriminability of pairs of two-component complex tones with identical small amplitude differences between the components of a pair. Discriminability seemed to depend upon the difference in their envelope-weighted instantaneous frequency fluctuations. In the study to be reported, four subjects matched a double-sideband suppressed-carrier (DSSC) signal to each member of pairs of two-component complex tones centered at frequencies from 500 to 4000 Hz. There were small, complementary amplitude differences between components of a pair of two-tone complex signals, while the amplitudes of the two components in the DSSC signal were equal. Listeners were also asked to discriminate between pairs of these complementary two-tone complexes. Data indicate that there is a relationship between the discriminability of the complementary two-component complexes and the perceived pitch of each complex. These data were used to test several variations of a (general) weighted time-average model to relate the pitch of each fluctuating two-tone complex to its averaged instantaneous frequency. In general, the model seems to hold for center frequencies below 4000 Hz where there are moderate frequency separations between the components of a complex. The model appears to be insensitive to the choice of weighting functions and the nature of the average.
Judgments of sound volume: Effects of signal duration, level, and interaural characteristics on the perceived extensity of broadband noise
Authors: Perrott David R. , Buell Thomas N.
Published: October 2005

While auditory stimuli are often described in terms of their apparent extensity, such descriptions have usually not been collected systematically. Moreover, the few deliberate attempts to evaluate image size have rarely gone beyond the classic parameters of stimulus frequency and intensity. In the present study a direct magnitude estimation procedure was employed. Seventeen subjects numerically estimated the apparent size of images produced by broadband noise stimuli. Under earphone listening conditions, signals were presented either dichotically (uncorrelated noise), diotically (correlated noise), or monaurally (noise led to a single earphone). The signals in each of these modes varied in duration (100, 300, 1000, and 3000 msec) and intensity level (60, 75, and 90 dB A weighted). Size estimates were plotted as power functions and analyzed with a repeated measures design analysis of variance. Consistent with previous research, the main effects of duration and intensity were both highly significant (p<0.001). In addition, a highly significant effect for mode of presentation was found (p<0.001). Across conditions, dichotic stimulation produced the largest images and monaural stimulation the smallest (about half the size of the diotic images). This last result is the first quantification of previous anecdotal observations. General implications of these results were discussed.
Detection and interaural time discrimination of a sinusoid masked by interaurally delayed white noise
Authors: Cohen Marion F. , Koehnke Janet
Published: October 2005

Masking-level differences and masked interaural time jnds were measured for a 560- and a 1000-Hz tone-burst signal. The masker, a diotic white noise, was interaurally time delayed by amounts ranging from no delay to one full period of the signal frequency. Results show that the size of the jnd varies systematically with the masking-level difference. Those masker delays which most benefit detection cause poorer signal interaural time discrimination.
Digital ray tracing in two-dimensional refractive fields
Authors: Andersen A. H. , Kak A. C.
Published: October 2005

This paper presents a review of digital ray tracing in two-dimensional refractive index fields. Since the refractive index fields are not assumed to have any particular symmetries or other special properties, the reviewed methods do not include the techniques developed in optics and in ocean acoustics. We have assumed general two-dimensional refractive index distributions such as would be encountered in ultrasonic computerized tomography. In this paper we have also reviewed digital ray linking, that is, finding a ray path that connects a given transmitter–receiver pair. Also discussed are the difficulties caused by the discrete representation of the refractive index fields and the different interpolation procedures that have been suggested to get around this problem.
Temporal and spatial fluctuations in single-path underwater acoustic wave fronts, II: Transmission over 270-nmi range
Authors: Broek H. W.
Published: October 2005

The fluctuations in phase and amplitude of 400-Hz pulses 10 ms long transmitted over a single 270-nmi path were measured at each receiver of an experimental installation of eleven bottomed at about 5000 ft on a slope near Bermuda. Seventh-order and eighth-order arrivals were employed. From the data obtained, computations were made of arrival angles and acoustic bearings of the source, delay fluctuations between receivers, autocorrelations and cross correlations of relative delays, and cross correlations of relative delays, and cross correlations and coefficients of variation of received signal amplitudes. Plots of cosines of phase (delay) fluctuations between two receivers versus receiver spacing show an exponential decline, with decay lengths of 450 to 800 ft for downslope separations and 1200 to 1700 ft for cross-slope pairs, as compared with 2600 and 4000 ft, respectively, in a 43-nmi experiment.
Temporal and spatial fluctuations in single-path underwater acoustic wave fronts, III: Transmission over 540-nmi range
Authors: Broek H. W.
Published: October 2005

In this third experiment of a series at three ranges, pulses of 400-Hz acoustic signal generated by a ship-suspended source were transmitted over a 540-nmi underwater path to an experimental installation of eleven receivers bottomed at about 5000 ft depth on a slope near Bermuda. The receivers covered distances of about 2300 ft in both the downslope and cross-slope directions. Relative delays of sound arriving downcoming along a single path were measured at each receiver. From these were computed the arrival angles and acoustic bearing of the source, the delay fluctuations between receivers 500, 940, and 2300 ft apart, the densities of delay fluctuations, and the spectra of delay fluctuations. Variance of delay at this range is approximately linear with receiver separation, and about 2.7 times as great as the variance in the 43-nmi experiment. The behavior of concurrent upcoming arrivals at seven of the receivers was found to be almost identical to that of the downcoming arrivals.
Pressure fluctuations on the surface of a parallelogram prism protruding from a rotating circular disk
Authors: Leu M. C. , Mote C. D.
Published: October 2005

The flow near a parallelogram prism bonded to the rim of a rotating circular disk was studied experimentally. Pressure fluctuations were measured on the lateral surfaces of the prism at various rotation speeds spanning a range in which the boundary layer on the disk surface near the disk outer radius is either laminar or turbulent. The results suggest that the fluctuating pressure is primarily caused by the shedding of vortices from the lateral sides of the prism. However, the fluctuating pressure is also strongly dependent upon the state of disk boundary layer—whether it is laminar or turbulent.
Acoustics of thunder: A quasilinear model for tortuous lightning
Authors: Ribner Herbert S. , Roy Dipankar
Published: October 2005

An approximate quasilinear theory of thunder generation by tortuous lightning channels has been developed herein. It was applied to predict the major features of thunder, with details of the rumble and roll; these cannot be accounted for by current nonlinear treatments that exclude tortuosity. The waveform forecast is deterministic for a specific channel configuration and observer location: it is in effect a mapping of the shape of lightning into the sound of thunder. The lightning stroke is modeled as a tortuous line emitting N-shaped pressure waves from points all along its length. Although emitted simultaneously, they arrive sequentially according to distance: the received pressure signature is essentially a convolution of an N wave with a channel-shape function. Thus the thunder spectrum approximates a product form: an N-wave spectrum modulated by another due to channel tortuosity. In computer simulation a lightning channel was approximated as a zig-zag chain of straight segments; resolution was down to ∼3 m to yield zero-crossing frequencies of order 200 Hz. Suitable 3-D shapes were generated, using appropriate deflection probabilities. The computer carried out the integration (here a summation) to produce the thunder pressure signature. With fast D/A, the output (a voltage) varies in real time; it was tape recorded for playback as audible synthetic thunder. Other calculations with ‘‘stylized’’ channel shapes showed how specific thunder features correlate one-to-one with geometric channel features. The emission from successive collinear segments was found to largely cancel, except as they approach perpendicularity to the sound rays: the latter case yields a focused thunderclap. Conversely, the uncanceled emission from corners or kinks in a lightning channel was identified as a major element in thunder emission. The corner effect accounts for the long duration (up to tens of seconds) of a real thunder signature compared with the single short thunderclap predicted for a long straight channel. The tortuous channel thunder predicted by the computer model was found to be compatible in (i) waveform appearance, (ii) spectral characteristics, and (iii) audible sound with real thunder (cf. bound-in soundsheet).
Scattering of acoustic waves by rigid cylindrical objects with sharp corners
Authors: Varadan V. K. , Varadan V. V. , Tsao S. J. , Neubauer W. G.
Published: October 2005

The T-matrix or Null Field approach is employed for studying scattering of acoustic waves by rigid cylindrical obstacles with sharp corners. A piecewise basis function is used to represent the surface field. The algebraic system of equations obtained from the resulting integral equations is solved for computing the surface and farfield amplitudes. Numerical results are presented for backscattering and bistatic scattering cross sections for square and intersecting circular cross sections and are compared with those obtained for smooth cross section, such as elliptical cross sections. Wavelengths down to one fifth of the maximum dimension of the section are considered. This frequency range is wide enough to definitively conclude that the dominate effect for objects with sharp corners is the interference of waves specularly reflected at such points also known as flash points. For smooth shapes such as the ellipse, the dominant effect is that of creeping waves. Schlieren photographs of a pulse propagating into the shadow of a cylinder with square cross sections are also given.
Resolution and variance in acoustic tomography
Authors: Eisler Thomas J. , New Ronald , Calderone Denise
Published: October 2005

Acoustic tomography is a proposed system for large-scale remote monitoring of ocean variables, especially the sound speed, as functions of position. In such a system, a number of sources transmit pulse codes which are detected at a number of receivers, so that the volume spanned by sources and receivers is crossed by a large number of acoustic paths (including multipaths). Travel time perturbations from a known reference state must be inverted to obtain estimates of sound-speed fluctuations from that reference state. In this paper, the Backus–Gilbert method is used to study the resolution and variance of such estimates in a horizontal ocean slice. Data kernels which are singular along ray paths are ‘‘quelled’’ by integration. Estimates are interpreted as weighted local averages of the unknown function and the weighting functions, or resolution kernels, which characterize resolution at a particular point, are illustrated at representative points. Global representations of resolution are also formulated and plotted. It is shown how resolution can be compromised for the purpose of reducing the variance of estimates due to statistical error. Such trade-off relations are discussed and exemplified.
Perceptual constancy of vowels in rapid speech
Authors: Johnson T. L. , Strange W.
Published: October 2005

In three experiments, we investigated the role of extrasyllabic speech context in the identification of /t/–vowel–/t/ syllables spoken at normal and rapid rates of articulation. Syllables spoken at the normal rate were identified with at least 95% accuracy regardless of the context in which they were presented. However, in experiment I, intrinsically long vowels in rapidly articulated syllables were identified with greater accuracy when the syllables were presented in rapid-rate sentence context than when they were presented in isolation or in normal-rate sentence context. Experiment II revealed that part of the performance deficit for excised isolated rapid syllables was attributable to sequential order effects among test items, and to listeners’ assumptions about whether the test syllables were or were not produced in isolation. In experiment III, test syllables were presented in the context of extracted portions of the rapid carrier sentences to determine the locus of the extrasyllabic information for vowel identity. The presence of the stressed syllable which immediately followed the test syllables in the carrier sentence was especially important for accurate identification of intrinsically long vowels in rapidly articulated syllables. Results are discussed in terms of intrinsic timing theories of speech production.
Masked discrimination of interaural time delays with narrow-band signal
Authors: Ito Yoshiko , Colburn H. Steven , Thompson Carl L.
Published: October 2005

Interaural time just-noticeable-difference (jnd) of a narrow-band noise masked by a wideband noise was measured for nine different interaural configurations of the masking noise at a fixed signal-to-noise ratio. The narrow-band noise was 1/3 octave wide centered about 500 Hz, and the wideband masker was bandpass filtered between 250 and 1500 Hz. Our results are in agreement with earlier results with tones [M. F. Cohen, J. Acoust. Soc. Am. Suppl. 1 64, S35 (1978); J. Acoust. Soc. Am. 70, 1289–1293 (1981); J. E. Slocum and R. M. Stern, J. Acoust. Soc. Am. Suppl. 1 68, S60 (1980)] and are the opposite of what may be expected from the results of binaural detection experiments: the jnd is largest for the interaurally phase reversed masker and smallest for the diotic masker. In addition, no consistent relation was observed between the size of the jnd and the perceptual location of the masker. Predicted jnds were calculated from a model based on the interaural phase difference of the stimuli in the two ears and were in rough agreement with the experimental results.
Curvature of sound decays in partially reverberant rooms
Authors: Bartel Thomas W. , Yaniv Simone L.
Published: October 2005

Measurements were conducted to investigate the departure from linearity of sound decays in partially reverberant rooms—that is, rooms, such as are found in office buildings and residences, that are less reverberant than laboratory reverberation chambers. The extent to which the nonlinearities in the decay curves could be reduced by means of an ensemble-averaging procedure was determined. Decay curves for five partially reverberant rooms, ranging in size from 45 to 425 m3, were tape recorded and played back at reduced speed into a real-time analyzer. Decay measurements were also performed in the NBS 425-m3 reverberation chamber. It was found that ‘‘smooth’’ decay curves, displaying a curvature characterized by a monotonically decreasing decay rate, could be obtained provided that the ensemble averages included decays recorded at several source and receiver locations. Thus, the rate of decay at any point in time for partially reverberant rooms could be precisely and unambiguously determined. The magnitude of the curvature was such that the percentage difference between the early decay rate and the decay rate averaged over a 25-dB range varied from approximately 2% to 40%, with the greatest differences occurring in rooms containing an absorptive ceiling and floor or an opening connecting them to other rooms.
Acoustic radiation pressure produced by a beam of sound
Authors: Chu Boa-Teh , Apfel Robert E.
Published: October 2005

The second-order force produced by a sound beam directed normally at a plane target is calculated. Previous theories on acoustic radiation pressures associated with plane acoustic waves are examined critically and erroneous results, where they exist, are noted and rectified. A number of general relations are established using a new approach which avoids the necessity of dealing with detailed solutions of the governing nonlinear equations. Some of the concepts inferred from known solutions obtained by previous authors require drastic revision in the light of the present study. Specifically, the notion that Rayleigh radiation pressure depends on the nonlinearity of the medium (while Langevin radiation pressure does not) is not true in the case where the medium is bound by a partially reflecting wall. Again, that the concept that Rayleigh radiation pressure depends on the acoustic field only through the energy density of the field is shown to be false. In one instance it is shown to depend also on how the field is maintained, while in another instance it does not appear to depend on the mean energy density of the field at all.
Ultrasonic absorption and dispersion in biological media: A postulated model
Authors: Sehgal Chandra M. , Greenleaf James F.
Published: October 2005

An integrated approach for the absorption of ultrasound by liquids and tissues is proposed from the solution of a one-dimensional wave equation of propagation. The proposed model explains the square and linear power dependence of absorption on frequency for liquids and tissues, respectively. The study also provides a new index, specific heat ratio (γ), in terms of which the physical and the chemical state and thus possibly the pathological state of a tissue can be defined quantitatively.
Quantitative ultrasonic backscatter measurements in the presence of phase distortion
Authors: O’Donnell M.
Published: October 2005

The accuracy of quantitative ultrasonic backscatter measurements has been investigated in the presence of phase distortion. Using both computer simulation and measurements on tissue phantoms, quantitative backscatter estimates have been obtained in the presence of phase distortions capable of producing significant artifacts in conventional B-scan images. The results of these studies suggest that quantitative measurements of the backscatter can be obtained in highly inhomogeneous tissue using conventional B-scan equipment.
The cochlear frequency map for the cat: Labeling auditory-nerve fibers of known characteristic frequency
Authors: Liberman M. Charles
Published: October 2005

Iontophoresis of horseradish peroxidase was used to label single auditory nerve fibers after determination of threshold tuning curves and rates of spontaneous discharge. The relation between characteristic frequency (CF) and cochlear longitudinal location is reconstructed from 52 labeled neurons in 16 cochleas. The length of the organ of Corti alotted to an octave of stimulus frequency increases steadily from low to high frequencies. Thus there is not a simple linear- distance-to-log frequency conversion. When comparing cochleas of different total length, the best predictor of CF at a given location is the distance from base or apex expressed as a percentage of the total length. The cochlear frequency map derived from these single-neuron labeling experiments is compared to maps derived by a number of different physiological and psychophysical techniques, and the significance of the similarities and differences is discussed.
Age effects in susceptibility to noise-induced hearing loss
Authors: Yanz Jerry L. , Abbas Paul J.
Published: October 2005

Several studies in recent years have suggested that susceptibility to noise-induced hearing loss is influenced by an animal’s age at the time of acoustic overstimulation. In the present experiment an attempt was made to learn more about age effects by integrating into a single study observations of the initial effects of noise exposure and the time course of postexposure threshold changes. Mice were exposed to noise at one of two ages (18 or 28 days). The threshold of the auditory compound action potential was estimated from the scalp-recorded electrical response immediately after the exposure and again at 5-and 30-days postexposure. These measures were compared with identical measures from yoked control subjects to determine the effects of noise exposure. Results indicate an interaction of age with exposure intensity and postexposure interval. Specifically, an age effect is seen only at the higher of two exposure intensities and only after a 30-day postexposure interval. Individual data suggest further that the existence of an age effect is determined not by the initial postexposure threshold shift, but rather by subsequent changes in threshold following exposure.
Arrays of random line arrays with constrained element separations
Authors: Lockwood J. C. , Thorn J. V. , Booth N. O.
Published: October 2005

In previous analyses of random arrays the element position probability density functions (pdf’s) assumed have allowed the possibility of elements being arbitrarily close together. When elements are close enough together for the received noise samples to be correlated, the directivity index (DI) of the array is reduced. In an array of random line arrays this DI reduction can be substantially eliminated by placing a constraint on the minimum interelement spacing allowed on each line. Expressions for the ensemble averages of the pattern function and the power pattern are derived by use of a pdf for each element position that excludes a small region centered on each of the previously chosen element positions on the same line. Calculated power patterns and gain patterns for arrays of random line arrays with constrained and unconstrained separations are compared.
Electromechanical analysis of nonaxisymmetrically loaded piezoelectric disks with electroded faces
Authors: Bogy D. B. , Bechtel S. E.
Published: October 2005

An approximate two-dimensional theory is used to study the electromechanical behavior of face electroded, circular, piezoelectric (PZT) disks of the type used in transducers. Solutions are obtained for the voltage generated in both free and forced motions due to nonaxisymmetric initial conditions and loading. Both free and simply supported edge conditions are also considered. Specific numerical results are obtained for certain cases and these results are compared with corresponding experimental observations. It is found that in the presence of electroded faces and insulated edges the general nonaxisymmetric problem reduces to an equivalent axisymmetric one involving only the extensional motions as far as the voltage difference between the electrodes is concerned. It is further observed that the output voltage time history is dominated by contributions due to radial modes of motion in the edge free case, but that only the thickness modes of motion contribute to this voltage in the simply supported case. This observation is relevant to transducer design since the analysis and results are vastly simpler in the latter case.
Periodic Rayleigh waves of finite amplitude on an isotropic solid
Authors: Kalyanasundaram N. , Anand G. V.
Published: October 2005

Existence of a periodic progressive wave solution to the nonlinear boundary value problem for Rayleigh surface waves of finite amplitude is demonstrated using an extension of the method of strained coordinates. The solution, obtained as a second-order perturbation of the linearized monochromatic Rayleigh wave solution, contains harmonics of all orders of the fundamental frequency. It is shown that the higher harmonic content of the wave increases with amplitude, but the slope of the waveform remains finite so long as the amplitude is less than a critical value.
Temporal and spatial fluctuations in single-path underwater acoustic wave fronts, I: Transmission from the first convergence zone at 43-nmi range
Authors: Broek H. W.
Published: October 2005

Pulses of 400-Hz acoustic signal 10 ms long were transmitted every 15 s for a period of 26 h from a ship-suspended source 1200 ft deep to an experimental installation of receivers 43 nmi away bottomed at about 5000 ft depth on a slope in the deep Atlantic near Bermuda. The set of receivers spanned distances of about 2300 ft in both the downslope and cross-slope directions. Delays (differences in arrival times) of every 24th pulse arriving downcoming along a single path were measured at each receiver. From these, characteristics of delay fluctuations (wave-front shape variations) were determined, including: relative fluctuations between pairs of receivers versus receiver spacing and time; densities of delay fluctuations; and variance of delay versus receiver separation. Plots of cosines of relative phase delays between two receivers versus receiver spacing show an exponential decline, with decay lengths of about 4000 ft for cross-slope separations and 2600 ft for downslope separations.
Precise model measurements versus theoretical prediction of barrier insertion loss in presence of the ground
Authors: Nicolas J. , Embleton T. F. W. , Piercy J. E.
Published: October 2005

Recent work on barrier performance, aimed at quantifying effects due to interference and scattering by atmospheric turbulence, has also indicated systematic deviations between measured results of diffraction and those predicted by widely used theories embodying known approximations. Model experiments indoors (no atmospheric turbulence and a known, controllable ground impedance) show systematic deviations, independent of frequency, up to 12 dB when compared with either first-order approximations of Macdonald’s diffraction theory or that of Kirchhoff. More exact evaluation of the diffraction integral [e.g., Hadden and Pierce, J. Acoust. Soc. Am. 69, 1266–1276 (1981)] or diffraction theory based on layer potential theory [e.g., Daumas, Acustica 40, 212–222 (1978)] provide agreement with measured results within ±1.5 dB under all experimental configurations investigated. An empirical correction based solely on such geometrical considerations as distance of source and receiver to the barrier and height of barrier, i.e., on the value of the angle of diffraction at the edge of the barrier, provides similarly good agreement. To obtain precise theoretical predictions of barrier performance under a wide range of configurations it is suggested that one use either calculations based on the recent formulation of Hadden and Pierce or some simple approximate theory plus this empirical correction based on diffraction angle.
Envelope representations of pinna impulse responses relating to three-dimensional localization of sound sources
Authors: Hiranaka Yukio , Yamasaki Hiro
Published: October 2005

Acoustical impulse responses of the external ear system are measured in order to investigate human three-dimensional auditory localization. A sound source of electric spark discharge is presented in nine directions for each of four vertical planes, 1.5 m from the center of the subject’s head. The results show that a human pinna works as a compound sound reflector which produces major reflected components within 350 μs. The relationship between the direction of the sound source and the impulse response is clearly shown by the use of an envelope formation technique and radial ray displays.
Acoustic propagation in random layered media
Authors: Levine Herbert , Willemsen Jorge F.
Published: October 2005

We study how the presence of small scale random layering may affect the interpretation of acoustic scattering data. Our methods include theoretical analysis based on the idea of localization of states, in conjunction with Monte Carlo simulations of particular layered systems suggested by interesting geophysical examples. We show that the random layering can produce dramatic effects by leading to a cutoff frequency for transmission through the system.
A computer simulation of acoustical image reconstruction
Authors: Yeager David M.
Published: October 2005

Acoustical holographic reconstruction techniques which were developed by Williams et al. [J. Acoust. Soc. Am. 68, 340–344 (1980)] have been simulated on a digital computer. Sound pressure and normal acoustic intensity images are reconstructed and graphically compared with their theoretical values for simple monopole and dual monopole configurations. Sources of error such as wraparound, aliasing, and nonuniform microphone response (magnitude and phase) are investigated. The resolution enhancement afforded by the reconstruction process is also demonstrated.
Sound propagation over Dickins Seamount in the Northeast Pacific Ocean
Authors: Ebbeson Gordon R. , Turner R. Glenn
Published: October 2005

The acoustic propagation losses between a 230-Hz cw source and a multi-hydrophone receiving system were measured over Dickins Seamount in the Northeast Pacific. The source was towed at depths of 18 and 184 m. The receiving system had hydrophones spaced in depth from 323 to 633 m. The measurements were made to a maximum range of 130 km with the receiver located at a range of 60 km from the seamount peak. The results show that the seamount cast an acoustic shadow over the receiver, increasing the propagation loss by up to 15 dB, when the source was shallow and in a position which enabled the seamount to intercept all of the deep refracted source energy. Back reflections from the seamount with levels 6 to 13 dB below the direct signal level were present when the shallow source was 3 to 5 km from the seamount peak. Downslope reflections enhanced the direct signal by up to 10 dB when the shallow source was within 3 km of the peak. Acoustic shadowing and reflection effects were minimal in the results for the deep source because most of the source energy propagated along the sound-channel axis above the seamount peak. The analysis indicates that ray theory is adequate for describing the reflection effects of the acoustic propagation but does not account for all of the acoustic energy in the shadow zone.