• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

Jun 1989

Volume 85, Issue 6, pp. 2255-2702

Page 2 of 6 Pages Previous Page Next Page | Jump to Page

Acoustic radiation from a shell with internal structures

M. El‐Raheb and P. Wagner

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2452-2464 (1989); (13 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
A method is developed to compute frequency response and acoustic radiation of a complex shell. The axisymmetric geometry of the shell includes cylindrical, conical, and spherical segments stiffened by discrete rings and bulkheads. The shell is coupled to internal masses and elastic frames. Shell segments are treated by transfer matrices. Rings, bulkheads, frames, and concentrated masses are treated by impedances at junctions of segments. The shell is coupled to an external acoustic fluid treated by Green’s function and curved surface elements. A major issue facing the method’s treatment of the fluid would be lack of existence or uniqueness encountered in the uncoupled, external acoustic problem at characteristic wavenumbers. By using a simple spherical shell, without internal structures, this potential hindrance is shown not to arise. A fuller application of the method awaits subsequent results.
Show PACS
43.40.Ey Vibrations of shells
43.40.At Experimental and theoretical studies of vibrating systems

Nearfield effects in acoustic scattering by submerged rigid bodies and elastic shells

G. C. Gaunaurd and M. F. Werby

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2465-2471 (1989); (7 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Old classic formulas to evaluate the farfield, general, differential scattering cross sections, and the farfield sonar or backscattering cross sections of submerged solid bodies and elastic shells are modified and generalized here to their nearfield region of validity. The formulation is developed in 2‐D by means of normal mode series, and in 3‐D by means of the extended boundary condition (EBC) approach. The nearfield expressions, which are the ones valid in the close proximity of targets, are shown to asymptotically reduce to the standard ones defined in their farfields as the distance between target and observation point increases. Many calculated examples are exhibited of bistatic angular distributions plotted versus aspect angle, and of backscattering cross sections plotted versus frequency, both in 2‐D and 3‐D, all evaluated in the nearfield. In the cases examined, which here include cylindrical shells and rigid spheroidal bodies, it is shown that the farfield values, given by the usual farfield expressions, are reached at distances of about five shell diameters (or spheroidal lengths) away. In connection with nearfield evaluations of scattering cross sections, it is of interest to predict the sound‐pressure fields transmitted inside a submerged, air‐filled shell. These internal fields in cylindrical shells have been studied here. Isobaric contours of the internally transmitted pressures are displayed in various graphs. These plots quantitatively show the spatial variations of the high‐pressure points (quasicaustics) that are developed internally, due to the resonance vibrations of the shell and its internal air column. The shell vibrations are mostly due to (flexural) Lamb waves circumferentially propagating around it.
Show PACS
43.40.Ey Vibrations of shells
43.20.Fn Scattering of acoustic waves
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries

Model‐based passive ranging

James V. Candy and Edmund J. Sullivan

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2472-2480 (1989); (9 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
Passive localization by use of acoustic propagation models, sometimes called ‘‘matched field processing’’ is usually carried out in three steps. First, some appropriate model is selected. Then, model parameters, usually taken from archival data or from auxiliary measurements, are introduced into the model. Finally, acoustic measurements of the field radiated by the source to be located are made that, in combination with the properly parametrized model, allow a solution for the source coordinates to be carried out. Here, such a model‐based approach is used in conjunction with a normal‐mode model. By coupling the procedure with a parameter estimation/identification scheme and using a horizontal (towed) array instead of the usual vertical array, it is shown that the model parameters need not be known a priori in order to carry out the solution. This is in contrast to the standard approach in which the modal functions must be computed directly from the model (wave equation) in order to solve the problem. It is still necessary to base the calculation on a model, but, surprisingly, the sound velocity profile, the ocean depth, and ocean bottom properties need not be known explicitly, since sufficient information to determine the range of the source can be inferred directly from the measured data themselves. Using a sophisticated acoustic propagation model to generate simulated data, coupled with various array processing techniques, the feasibility of the approach is demonstrated.
Show PACS
43.60.Gk Space-time signal processing, other than matched field processing
43.30.Zk Experimental modeling

Sound propagation in the ear canal and coupling to the eardrum, with measurements on model systems

Michael R. Stinson and Shyam M. Khanna

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2481-2491 (1989); (11 pages) | Cited 7 times

Full Text: | Download PDF

Show Abstract
A theoretical model of sound propagation in the ear canal is described, which takes into account both the complicated geometry of real ear canals and the distributed acoustical load presented by the eardrum. The geometry of the ear canal enters the theory in the form of a cross‐sectional area function relative to a curved axis that follows the center of the ear canal. The tympanic membrane forms part of the ear canal wall and absorbs acoustical energy over its surface. Its motion leads to a driving term that must be added to the horn equation describing the pressure distribution in the ear canal. The sound field within the canal is assumed to be effectively one dimensional, depending only on longitudinal position along the canal. Experiments using model ear canals of uniform cross section were performed to test the ability of the theory to handle distributed loads. Sound‐pressure distributions within each model canal were measured using a probe microphone. The behavior of the eardrum was simulated using either a distributed, locally reacting impedance or a mechanically driven piston. The agreement between theory and experiment is good up to a nominal upper frequency limit at which the ratio of canal width to wavelength is 0.25. It is estimated that the theory is applicable in ear canals of cats for frequencies at least as high as 25 kHz and in human ear canals to at least 15 kHz.
Show PACS
43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
43.64.Bt Models and theories of the auditory system
43.64.Yp Instruments and methods
43.20.Mv Waveguides, wave propagation in tubes and ducts

Specification of the geometry of the human ear canal for the prediction of sound‐pressure level distribution

Michael R. Stinson and B. W. Lawton

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2492-2503 (1989); (12 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
The geometry of 15 human ear canals has been studied. Silicone rubber molds were made of the ear canals of human cadavers, and a mechanical probe system was used to obtain approximately 1000 coordinate points over the surface of each mold. The data points were accurate to about 0.03 mm in each of the three space directions, allowing ample resolution of surface detail. The measurements have been summarized as individual ear canal area functions, the area of cross‐sectional slices normal to a curved central axis following the bends of the canal. Large intersubject differences were found, but several overall trends were evident in the area functions. Accurate specification of the canal geometry has lead to improved predictions of the sound‐pressure distribution along the human ear canal at frequencies greater than 8 kHz. Such predictions are relevant to the development of high‐frequency audiometric methods, high‐fidelity hearing aids, and to the interpretation of experiments in physiological and psychological acoustics.
Show PACS
43.64.Ha Acoustical properties of the outer ear; middle-ear mechanics and reflex
43.64.Yp Instruments and methods
43.64.Bt Models and theories of the auditory system
43.20.Mv Waveguides, wave propagation in tubes and ducts

A closed‐form solution for removing the dead time effects from the poststimulus time histograms

Qi Bi

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2504-2513 (1989); (10 pages)

Full Text: | Download PDF

Show Abstract
Discharge patterns from cochlear nerve fibers contain important information about acoustic stimuli and encoding schemes of the peripheral auditory system. Yet these patterns are distorted due to refractory or dead time effects. By modeling discharges from peripheral auditory nerves as a self‐exciting Poisson process, the effects of dead time on a poststimulus time histogram can be determined, assuming the recovery time does not depend on acoustic stimuli. If the recovery function is known, a closed‐form formula is available to remove the dead time distortions from the poststimulus time histogram.
Show PACS
43.64.Pg Electrophysiology of the auditory nerve
43.64.Bt Models and theories of the auditory system
43.64.Yp Instruments and methods
43.64.Nf Cochlear electrophysiology

Stimulus dependencies of the gerbil brain‐stem auditory‐evoked response (BAER). I: Effects of click level, rate, and polarity

Robert Burkard and Herbert F. Voigt

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2514-2525 (1989); (12 pages) | Cited 6 times

Full Text: | Download PDF

Show Abstract
Three experiments evaluating the effects of various stimulus manipulations on the click‐evoked gerbil brain‐stem auditory‐evoked response (BAER) are reported. In experiment 1, click polarity and level were covaried. With increasing click level, there is a parallel decrease in the latency of the first five BAER peaks (i–v) and an increase in BAER peak amplitudes. Mean wave i amplitude was greater for rarefaction than condensation clicks at high click levels; mean wave v amplitude was greater for condensation clicks at higher click levels. Experiment 2 covaried click rate and polarity. The latency of the BAER peaks increased with increasing click repetition rate. This rate‐dependent latency increase was greater for the later BAER peaks, resulting in an increase in the i–v interval with increasing click rate. As rate increased, the amplitudes of waves i and v decreased monotonically, whereas the amplitudes of waves ii–iv were largely uninfluenced by click rate. As in experiment 1, mean wave i amplitude was greater for rarefaction clicks, whereas mean wave v amplitude was greater for condensation clicks. The magnitude of these polarity dependencies on waves i and v amplitude decreased with increasing click rate. Experiment 3 evaluated the effects of click polarity on BAERs to high‐intensity (100 dB pSPL) clicks presented at a rate of 10 Hz. In eight of ten gerbils evaluated, wave i amplitude was greater to rarefaction clicks, and, in all ten animals, wave v amplitude was greater to condensation clicks. The effects of click level and rate on BAER peak amplitudes, latencies, and interwave intervals are reminiscent of stimulus dependencies reported for the human BAER. The effects of click polarity on the amplitudes of waves i and v of the gerbil BAER have also been reported for the human BAER.
Show PACS
43.64.Qh Electrophysiology of the auditory central nervous system
43.64.Ri Evoked responses to sounds
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Stimulus dependencies of the gerbil brain‐stem auditory‐evoked response (BAER). II: Effects of broadband noise level and high‐pass masker cutoff frequency across click polarity

Robert Burkard and Herbert F. Voigt

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2526-2536 (1989); (11 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Two experiments concerning the effects of masking noise on the gerbil brain‐stem auditory‐evoked response (BAER) are reported. Experiment 1 evaluated the effects of broadband masking noise on the BAER obtained to condensation and rarefaction clicks. With increasing noise level, there was an increase in BAER peak latencies, an increase in the i–v interval, and a decrease in peak amplitudes. Experiment 2 evaluated the effects of high‐pass masking noise on the BAER obtained to condensation and rarefaction clicks. Both high‐pass responses and derived‐band responses were evaluated. For high‐pass responses, with decreasing masker cutoff frequency, there was an increase in BAER peak latencies, a decrease in the i–v interval, and a decrease in peak amplitudes. For derived‐band responses, with decreasing derived‐band frequency, there was an increase in peak latencies and a decrease in the i–v interval. A comparison of wave i and wave v amplitudes across derived‐band frequency demonstrates a greater contribution of high‐frequency cochlear regions to wave i than wave v. Small, insignificant, effects of click polarity on BAER peak amplitudes were observed. These trends were in the direction seen in a companion paper [R. Burkard and H. F. Voigt, J. Acoust. Soc. Am. 85, xxx–xxxx (1989)] and were, in general, reduced by the presence of broadband or high‐pass maskers.
Show PACS
43.64.Qh Electrophysiology of the auditory central nervous system
43.64.Ri Evoked responses to sounds
43.66.Dc Masking

Repetition rate and signal level effects on neuronal responses to brief tone pulses in cat auditory cortex

D. P. Phillips, S. E. Hall, and J. L. Hollett

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2537-2549 (1989); (13 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
This study describes the effects on the spike count, spike timing, and entrainment of cat auditory cortex neurons of parametric variations in the repetition rate and amplitude of a brief, characteristic frequency tone pulse. Data were obtained from single neurons in barbiturate‐anesthetized cats to which signals were presented monaurally to the ear contralateral to the recording electrode. All neurons showed low‐pass sensitivity to tone repetition rate. In cells with a monotonic rate response, the effect of an increasing stimulus level was to elevate the response rate and to extend performance to higher repetition rates. In nonmonotonic cells, cutoff frequencies (for repetition rate) varied with overall spike count. Latent periods increased with increases in repetition rate. This effect developed over the first few stimulus trials at any given repetition rate. Spike entrainment to the tone pulses varied with both repetition rate and signal level. Increases in signal level improved entrainment for responses to stimuli presented at low repetition rates, but entrainment at high repetition rates always saturated at significantly imperfect levels.
Show PACS
43.64.Qh Electrophysiology of the auditory central nervous system
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Spectrotemporal analysis and cochlear hearing impairment: Effects of frequency selectivity, temporal resolution, signal frequency, and rate of modulation

Joseph W. Hall, III and John H. Grose

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2550-2562 (1989); (13 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
The detection of 500‐ or 2000‐Hz pure‐tone signals in unmodulated and modulated noise was investigated in normal‐hearing and sensorineural hearing‐impaired listeners, as a function of noise bandwidth. Square‐wave modulation rates of 15 and 40 Hz were used in the modulated noise conditions. A notched noise measure of frequency selectivity and a gap detection measure of temporal resolution were also obtained on each subject. The modulated noise results indicated a masking release that increased as a function of increasing noise bandwidth, and as a function of decreasing modulation rate for both groups of listeners. However, the improvement of threshold with increasing modulated noise bandwidth was often greatly reduced among the sensorineural hearing‐impaired listeners. It was hypothesized that the masking release in modulated noise may be due to several types of processes including across‐critical band analysis (CMR), within‐critical band analysis, and suppression. Within‐band effects appeared to be especially large at the higher frequency region and lower modulation rate. In agreement with previous research, there was a significant correlation between frequency selectivity and masking release in modulated noise. At the 500‐Hz region, masking release was correlated more highly with the filter skirt and tail measures than with the filter passband measure. At the 2000‐Hz region, masking release was correlated more with the filter passband and skirt measures than with the filter tail measure. The correlation between gap detection and masking release was significant at the 40‐Hz modulation rate, but not at the 15‐Hz modulation rate. The results of this study suggest that masking release in modulated noise is limited by frequency selectivity at low modulation rates, and by both frequency selectivity and temporal resolution at high modulation rates. However, even when the present measures of frequency selectivity and temporal resolution are both taken into account, significant variance in masking release still remains unaccounted for.
Show PACS
43.66.Dc Masking
43.66.Pn Binaural hearing
43.66.Sr Deafness, audiometry, aging effects

Detecting single‐cycle frequency modulation imposed on sinusoidal, harmonic, and inharmonic carriers

Robert P. Carlyon and Richard J. Stubbs

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2563-2574 (1989); (12 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Thresholds for detecting frequency modulation (FM) of various carriers were measured in quiet and in noise. The carriers were either pure tones, harmonic complexes, or inharmonic complexes. The modulator was always a single cycle of a 12.5‐Hz sinusoid. When the carrier was a complex tone, each component of that carrier was modulated by the same percentage of its starting frequency. This is the form of FM that occurs when the fundamental frequency (F0) of a complex sound is modulated. Threshold was defined in terms of this percentage frequency change. Two phases of the modulator were used, producing percepts of either upward or downward frequency glides. Experiment 1 used sinusoidal carriers with frequencies between 200 and 2400 Hz. Thresholds were constant for carrier frequencies of 1200 Hz and above, increased below 800 Hz, and were higher for the ‘‘down’’ than for the ‘‘up’’ glides, especially with low carrier frequencies. Experiment 2 measured thresholds for carriers consisting of three adjacent harmonics of complexes with F0’s of 50, 100, and 200 Hz as a function of the frequency of the center component of each complex (CF). Thresholds varied with CF in a similar way to those for the pure‐tone carriers. In the frequency region 1200–2400 Hz, where thresholds did not vary with CF, they did not vary systematically with F0. Experiment 3 compared thresholds for a 20‐component harmonic complex with those for an inharmonic complex. Thresholds were only slightly lower for the harmonic complex than for the inharmonic complex when presented in quiet, but were much lower when the complexes were presented in bursts of pink noise. Thresholds in noise for the completely harmonic complex were also lower than those for 20‐component complexes in which only five adjacent components shared a harmonic relationship. It was concluded that a harmonic relationship between components occupying widely different frequency regions aids the detection of frequency modulation, particularly in the presence of noise.
Show PACS
43.66.Fe Discrimination: intensity and frequency
43.66.Hg Pitch
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.72.-p Speech processing and communication systems

Modulation masking: Effects of modulation frequency, depth, and phase

Sid P. Bacon and D. Wesley Grantham

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2575-2580 (1989); (6 pages) | Cited 50 times

Full Text: | Download PDF

Show Abstract
Modulation thresholds were measured for a sinusoidally amplitude‐modulated (SAM) broadband noise in the presence of a SAM broadband background noise with a modulation depth (mm) of 0.00, 0.25, or 0.50, where the condition mm=0.00 corresponds to standard (unmasked) modulation detection. The modulation frequency of the masker was 4, 16, or 64 Hz; the modulation frequency of the signal ranged from 2–512 Hz. The greatest amount of modulation masking (masked threshold minus unmasked threshold) typically occurred when the signal frequency was near the masker frequency. The modulation masking patterns (amount of modulation masking versus signal frequency) for the 4‐Hz masker were low pass, whereas the patterns for the 16‐ and 64‐Hz maskers were somewhat bandpass (although not strictly so). In general, the greater the modulation depth of the masker, the greater the amount of modulation masking (although this trend was reversed for the 4‐Hz masker at high signal frequencies). These modulation‐masking data suggest that there are channels in the auditory system which are tuned for the detection of modulation frequency, much like there are channels (critical bands or auditory filters) tuned for the detection of spectral frequency.
Show PACS
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music
43.66.Dc Masking

The precedence effect: No evidence for an ‘‘active’’ release process found

Jens Blauert, Georges Canévet, and Thierry Voinier

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2581-2586 (1989); (6 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Hafter et al. [Auditory Function: The Neurobiological Bases for Hearing (Wiley, New York, 1988)] have reported that ‘‘post‐onset adaptation,’’ as measured with trains of high‐frequency clicks in a lateralization paradigm, can instantly be released by presentation of an additional, short trigger signal, which is spectrally different from the click trains. As post‐onset saturation may be one of the psychoacoustic components of the precedence effect, it has been investigated whether suitable trigger signals might also induce a release from echo inhibition. However, no evidence for such an ‘‘active’’ release process could be observed in a number of exploratory precedence‐effect settings.
Show PACS
43.66.Pn Binaural hearing
43.66.Qp Localization of sound sources

Detection of gaps in sinusoids and pulse trains by patients with cochlear implants

Robert V. Shannon

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2587-2592 (1989); (6 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
Gap detection thresholds were measured in patients with the Nucleus and Symbion cochlear implants as a function of several current waveform parameters. Detection of gaps in an electrical sinusoidal stimulus or in a train of biphasic pulses by implanted patients was similar to detection of gaps in comparable acoustic stimuli by normal listeners. Threshold gaps were 20–50 ms for low‐level stimuli and improved with stimulus level to 2–5 ms for high‐level stimuli. Gap detection performance was not affected by the electrode position in the cochlea or by the distance between stimulating electrodes. The data from most patients were well fitted by a trading relation between the duration of the gap and the square of stimulus intensity, indicating energy detection. The similarity of gap thresholds for normal subjects and implant patients suggests that many details of the peripheral neural activity are probably not important for this task, and that there is no retrocochlear loss of auditory temporal resolution with sensorineural hearing loss.
Show PACS
43.66.Ts Auditory prostheses, hearing aids
43.66.Mk Temporal and sequential aspects of hearing; auditory grouping in relation to music

Speech perception studies using a multichannel electrotactile speech processor, residual hearing, and lipreading

R. S. C. Cowan, J. I. Alcantara, L. A. Whitford, P. J. Blamey, and G. M. Clark

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2593-2607 (1989); (15 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Three studies are reported on the speech perception of normally hearing and hearing‐impaired adults using combinations of visual, auditory, and tactile input. In study 1, mean scores for four normally hearing subjects showed that addition of tactile information, provided through the multichannel electrotactile speech processor, to either audition alone (300‐Hz low‐pass‐filtered speech) or lipreading plus audition resulted in significant improvements in phoneme and word discrimination scores. Information transmission analyses demonstrated the effectiveness of the tactile aid in providing cues to duration, F1 and F2 features for vowels, and manner of articulation features for consonants, especially features requiring detection and discrimination of high‐frequency information. In study 2, six different cutoff frequencies were used for a low‐pass‐filtered auditory signal. Mean scores for vowel and consonant identification were significantly higher with the addition of tactile input to audition alone at each cutoff frequency up to 1500 Hz. The mean speechtracking rate was also significantly increased by the additional tactile input up to 1500 Hz. Study 3 examined speech discrimination of three hearing‐impaired adults. Additional information available through the tactile aid was shown to improve speech discrimination scores; however, the degree of increase was inversely related to the level of residual hearing. Results indicate that the electrotactile aid may be useful for patients with little residual hearing and for the severely to profoundly hearing impaired, who could benefit from the high‐frequency information presented through the tactile modality, but unavailable through hearing aids.
Show PACS
43.66.Wv Vibration and tactile senses
43.66.Sr Deafness, audiometry, aging effects
43.66.Ts Auditory prostheses, hearing aids
43.71.Rt Sensory mechanisms in speech perception

Kinematic, acoustic, and perceptual analyses of connected speech produced by Parkinsonian and normal geriatric adults

Karen Forrest, Gary Weismer, and Greg S. Turner

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2608-2622 (1989); (15 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Acoustic and kinematic analyses, as well as perceptual evaluation, were conducted on the speech of Parkinsonian and normal geriatric adults. As a group, the Parkinsonian speakers had very limited jaw movement compared to the normal geriatrics. For opening gestures, jaw displacements and velocities produced by the Parkinsonian subjects were about half those produced by the normal geriatrics. Lower lip movement amplitude and velocity also were reduced for the Parkinsonian speakers relative to the normal geriatrics, but the magnitude of the reduction was not as great as that seen in the jaw. Lower lip closing velocities expressed as a function of movement amplitude were greater for the Parkinsonian speakers than for the normal geriatrics. This increased velocity of lower lip movement may reflect a difference in the control of lip elevation for the Parkinsonian speakers, an effect that increased with the severity of dysarthria. Acoustically, the Parkinsonian subjects had reduced durations of vocalic segments, reduced formant transitions, and increased voice onset time compared to the normal geriatrics. These effects were greater for the more severe, compared to the milder, dysarthrics and were most apparent in the more complex, vocalic gestures.
Show PACS
43.70.Dn Disordered speech
43.71.Lz Speech perception by the aging

Application of an auditory model to speech recognition

Jordan R. Cohen

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2623-2629 (1989); (7 pages) | Cited 4 times

Full Text: | Download PDF

Show Abstract
Some aspects of auditory processing are incorporated in a front end for the IBM speech‐recognition system [F. Jelinek, ‘‘Continuous speech recognition by statistical methods,’’ Proc. IEEE 64 (4), 532–556 (1976)]. This new process includes adaptation, loudness scaling, and mel warping. Tests show that the design is an improvement over previous algorithms.
Show PACS
43.72.Ne Automatic speech recognition systems
43.71.Qr Neurophysiology of speech perception
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech

Tuning of bells by a linear programming method

R. G. J. Mills

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2630-2633 (1989); (4 pages)

Full Text: | Download PDF

Show Abstract
A carillon bell is tuned by the removal of metal from the inner surface of the bell. Van Heuven [Acoustical Measurements on Church‐Bells and Carillons (De Gebroeders van Cleef, ’s‐Gravenhage, The Netherlands, 1949), Chap. IV] determined a set of tuning curves and derived a set of equations that relate the amount of metal removed to the relative alterations in the partial frequencies. This paper uses these equations as constraints in the formulation of the tuning problem as a linear program. An example illustrates the procedure.
Show PACS
43.75.Kk Bells, gongs, cymbals, mallet percussion, and similar instruments

Differentiation between acutely ischemic myocardium and zones of completed infarction in dogs on the basis of frequency‐dependent backscatter

Keith A. Wear, Mark R. Milunski, Samuel A. Wickline, Julio E. Perez, Burton E. Sobel, and James G. Miller

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2634-2641 (1989); (8 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
The goal of this work was to determine whether the frequency dependence of apparent backscatter coefficient (not corrected for attenuation within the myocardium) could differentiate completed, remote infarction from acute myocardial injury in vivo. Myocardial infarcts were produced in six dogs by coronary artery occlusion. One to 12 months later, acute ischemic injury was induced in each dog by ligation of a coronary artery that supplied a region of myocardium adjacent to the established infarct. Infarct, ischemic, and normal regions were interrogated with a 5‐MHz, circular, 0.5‐in. diam, broadband, focused, piezoelectric transducer mounted in a water‐filled stand‐off device placed against the exposed, beating heart. Apparent backscatter coefficients were measured over the range of frequencies from 3–7 MHz. The frequency dependence was obtained from the slope of log apparent backscatter coefficient versus log frequency. No significant difference in frequency dependence was found between normal and acutely ischemic myocardium for periods of up to 2 h of ischemia. In contrast, frequency dependence in regions of remote infarct (1.8±0.1, mean±standard error) was significantly lower than that in acutely ischemic or nonischemic regions (2.3±0.1) (p<0.01). These results suggest that remote myocardial infarction can be differentiated from acutely injured but still potentially salvageable myocardium in vivo on the basis of the frequency dependence of backscatter.
Show PACS
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
43.80.Qf Medical diagnosis with acoustics

Range estimation by echolocation in the bat Eptesicus fuscus: Trading of phase versus time cues

Dieter Menne, Ingrid Kaipf, Inge Wagner, Joachim Ostwald, and Hans‐Ulrich Schnitzler

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2642-2650 (1989); (9 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
Bats of the species Eptesicus fuscus have been trained to discriminate a stationary simulated target from a target with a virtual distance that jitters from sound to sound. Similar to Simmons [Science 207, 1336–1338 (1979)], a jitter‐detection threshold below 1 μs was found. However, Simmons’ decreased performance at a time delay jitter of 30 μs could not be replicated , a critical feature used to postulate the idea that bats employ a coherent cross‐correlation receiver for ranging. Such a receiver uses all phase information in the signal for delay estimation and therefore will be biased by phase manipulations. To test for such a bias, a phase jitter of ±45° and a time jitter in the echo were overlaid. It was not found that there was a combination of both where their effects canceled. Full phase information is thus not used in delay estimation. However, bats were able to detect a pure phase jitter, e.g., polarity inversion of the signal. Bats could also detect phase jitter in the presence of randomized time jitter and vice versa. Phase jitter and time jitter, therefore, are separable features for a bat. The underlying physiological mechanism is not clear.
Show PACS
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms

Masked tonal hearing thresholds in the beluga whale

C. S. Johnson, M. W. McManus, and D. Skaar

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2651-2654 (1989); (4 pages) | Cited 19 times

Full Text: | Download PDF

Show Abstract
Masked tonal thresholds were measured for a beluga whale at one noise level and 32 frequencies between 40 Hz and 115 kHz. Critical ratios were estimated and compared with those previously measured for the bottlenose dolphin. Beluga whale critical ratios were found to be about 3 dB lower than those of the bottlenose dolphin. Absolute tonal thresholds were extended below previous measurements to 40 Hz.
Show PACS
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
43.66.Dc Masking

Spherical nearfield calibration array for three‐dimensional scanning

A. L. Van Buren

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2655-2660 (1989); (6 pages)

Full Text: | Download PDF

Show Abstract
Nearfield calibration arrays (NFCAs) are used to determine the farfield acoustic radiation from a transducer by measurements made in the nearfield. The original Trott NFCAs [W. J. Trott, Underwater Sound Ref. Lab. Rep. No. 55 (1961); also J. Acoust. Soc. Am. 36, 1557–1568 (1964)] were planar arrays. More recently, cylindrical NFCAs have been developed for determining the azimuthal radiation pattern of an enclosed transducer. This paper describes a spherical NFCA for determining the full three‐dimensional radiation pattern of an enclosed transducer. In theory, the NFCA consists of a large number of discrete hydrophone elements arranged over a spherical surface in N equispaced constant latitude bands. In practice, the array can be synthesized by use of a single semicircular arc containing relatively few elements and by either rotation of the transducer or revolution of the arc about the polar axis. Individual hydrophone sensitivities (both amplitude and phase) are adjusted so that the NFCA serves as a plane‐wave filter for acoustic radiation originating from inside the sphere. The relative sensitivities, called shading coefficients, are computed using the NFCA reciprocity principle and a least‐squares procedure. Only a few sets of N/2 [or (N+1)/2, if N is odd] shading coefficients are required for full three‐dimensional operation of the NFCA over a frequency range of 3 oct or more. Design criteria are discussed and example numerical results are presented.
Show PACS
43.58.Vb Calibration of acoustical devices and systems
43.30.Sf Acoustical detection of marine life; passive and active
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance

A class of density profiles for constructing analytical solutions to a variable‐density parabolic equation

J. S. Robertson

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2661-2662 (1989); (2 pages)

Full Text: | Download PDF

Show Abstract
A class of depth‐dependent density profiles is described that permits the construction of analytical solutions to a variable‐density parabolic equation (VDPE). These solutions can serve as accuracy benchmarks for numerical algorithms that solve VDPEs.
Show PACS
43.20.Bi Mathematical theory of wave propagation
43.30.Bp Normal mode propagation of sound in water

Phase velocity of Lamb waves on a spherical shell: Approximate dependence on curvature from kinematics

Philip L. Marston

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2663-2665 (1989); (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The phase velocity cl along the outer surface of a thick shell for Lamb waves may be calculated as a function of frequency by use of Watson transform methods. For thick shells, this cl is offset from Lamb’s result for a flat plate of the same thickness h. This discrepancy may be removed by distinguishing the velocity along the outer surface (of radius a) from the velocity along a curve corresponding to the average radius [a−(h/2)] for the shell. The resulting expression in h/a facilitates an improved approximation of cl from Lamb’s analysis. The approximations may be useful in scattering calculations for cases where cl exceeds the speed of sound in the surrounding fluid.
Show PACS
43.20.Fn Scattering of acoustic waves
43.30.Jx Radiation from objects vibrating under water, acoustic and mechanical impedance
43.40.Ey Vibrations of shells

Off‐resonance contributions to acoustical bubble spectra

Kerry Commander and Elan Moritz

J. Acoust. Soc. Am. Volume 85, Issue 6, pp. 2665-2669 (1989); (5 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
Comparisons of experimental optical and acoustical bubble size spectra disagree in size distribution at the low end of the spectrum. Previous methods of obtaining acoustic bubble size information relied strictly on resonant acoustical scattering and absorption theory. For some plausible distributions, these traditional methods greatly overpredict the number of bubbles present in a volume of fluid for bubble radii of 50 μ or less. Two cases are investigated that show the magnitude of departure from a priori bubble size distributions and are used to benchmark traditional acoustical scattering and absorption‐based methods for obtaining spectra. A third possible bubble distribution is presented that is consistent with resonant approximation theory; however, the acoustic properties of this distribution are inconsistent with measurements from naturally occurring bubble populations. It is argued that off‐resonance contributions to acoustical bubble spectra determinations need to be included.
Show PACS
43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.20.Fn Scattering of acoustic waves
43.30.Gv Backscattering, echoes, and reverberation in water due to combinations of boundaries
Page 2 of 6 Pages Previous Page Next Page | Jump to Page
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close