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Journal of the Acoustical Society of America

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Jun 1976

Volume 59, Issue 6, pp. 1259-1516

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Direct image reconstruction of anomalies in a plane via physical optics farfield inverse scattering

Norman Bleistein

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1259-1264 (1976); (6 pages) | Cited 2 times

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This paper shows how to process backscattered acoustic data to directly generate the image of an anomaly in a plane such as an anticline, syncline, or fault. The result is based on a physical optics farfield inverse scattering (POFFIS) identity. This identity states that a phase‐ and range‐normalized scattering amplitude is proportional to a function which is unity in the region of the anomaly and zero outside that region.
Subject Classification: [43]20.30, [43]20.15; [43]40.50.
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43.20.+g General linear acoustics
43.40.+s Structural acoustics and vibration

Theorem on the scattering and the absorption cross section for scattering of plane, time‐harmonic, elastic waves

T. H. Tan

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1265-1267 (1976); (3 pages)

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In a homogeneous, isotropic, perfectly elastic medium a scattering obstacle of finite extent is present. When a plane, time‐harmonic, elastic compressional (P) or shear (S) wave is incident on it, the extinction cross section (i.e., the sum of the scattering and the absorption cross section) of the obstacle is directly related to the far‐zone amplitude of the particle displacement of the scattered wave, observed exactly behind the obstacle. This relationship is discussed. In spite of the fact that in elastodynamic scattering the scattered P wave as well as the scattered s wave contribute to the time‐averaged scattered power, the extinction cross section appears to depend only on the value of that farfield scattered‐wave amplitude which is of the same type (P or S) as the incident wave.
Subject Classification: [43]20.15, [43]20.30.
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43.20.+g General linear acoustics

Use of a spherical concave reflector for jet‐noise‐source distribution diagnosis

W. T. Chu and R. E. Kaplan

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1268-1277 (1976); (10 pages) | Cited 1 time

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An account on the development of a directional microphone system for jet‐noise‐source strength distribution measurements is given. The system selected is based on the imaging principle of a spherical concave reflector. As expected, the system is diffraction limited; a loss of resolution results. A special technique is discussed to recover the axial‐source strength distribution from the diffracted data. Sample experiments are presented to show the successful application of such a system for jet noise measurements.
Subject Classification: [43]28.65; [43]50.55; [43]85.62.
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43.28.+h Aeroacoustics and atmospheric sound
43.50.+y Noise: its effects and control
43.58.+z Acoustical measurements and instrumentation

Additional sound absorption measurements in near‐freezing sea water

G. R. Garrison, E. W. Early, and T. Wen

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1278-1283 (1976); (6 pages)

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Sound propagation measurements at 10, 20, 30, 40, and 60 kHz were made in April 1974 under the ice pack near Pt. Barrow, Alaska. Absorption coefficients were calculated for each frequency and have been reported in detail [G. R. Garrison et al., J. Acoust. Soc. Am. 58, 608–619 (1975)]. In April 1975, an attempt was made to furnish more accurate results at the lower frequencies by measuring the absorption at 7, 13, 20, 30, and 60 kHz. The 1975 measurements gave the following results for the absorption coefficients dB/kyd at a temperature of −1.6 °C and a salinity of 32%: 0.2±0.4 at 7.1 kHz; no data at 13 kHz because of transducer failure; 3.9±0.2 at 20 kHz; 7.2±0.3 at 30 kHz; and 13.1±0.5 at 60 kHz. These values indicate a relaxation frequency, due to MgSO4, of 36±3 kHz, which is slightly above our previous results, but still much lower than that predicted by the Schulkin–Marsh equation for a temperature of −1.6 °C.
Subject Classification: [43]30.20.
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92.10.Vz Underwater sound

Spatial interfrequency correlation effects in a surface‐scatter channel

J. F. McDonald, F. B. Tuteur, and J. G. Zornig

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1284-1293 (1976); (10 pages) | Cited 1 time

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The effect of spatial separation on the cross correlation between the system response functions for a two‐receiver surface‐scatter channel is investigated. The system response at the two receivers is determined for all possible pairs of frequencies. The analysis assumes relatively close separation of receivers and uses the Fresnel‐corrected model for surface scatter in the specular direction. The surface is assumed to be Gaussian, with typical size of boundary deformations small compared to typical Fresnel zones.The analysis shows that the correlation is approximately maximum for zero‐frequency separation and drops off at a rate determined by the reverberation time. For small reverberation times and small grazing angles correlation may extend over fairly large values of frequency difference. The effect of spatial separation is generally a reduction in correlation and a more rapid decrease of correlation with frequency, but this can be compensated to some extent by time shift between the two system responses. Experimental evidence is included to support the theoretical predictions presented.
Subject Classification: [43]30.20; [43]20.15; [43]60.20.
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92.10.Vz Underwater sound
43.20.+g General linear acoustics
43.60.+d Acoustic signal processing

Evaluation of transducer window materials

E. Eugene Mikeska and John A. Behrens

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1294-1298 (1976); (5 pages) | Cited 3 times

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Acoustic measurements of insertion loss and echo reduction at normal incidence were made for thin plates of eight materials for evaluation of their use in underwater sound transducers in the frequency range 50–500 kHz. Materials tested included Lucite; silicone rubber RTV– 560; the commercial polyurethane products PRC–1527, CPC–19, Scotchcast 8, and Scotchcast 221; and two of these materials with talc added during curing to vary the properties. Values of longitudinal sound velocity, attenuation constant, and characteristic impedance are derived from comparison of theoretical and measured characteristics.
Subject Classification: [43]30.30; [43]40.55; [43]55.75; [43]85.40.
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92.10.Vz Underwater sound
43.40.+s Structural acoustics and vibration
43.55.+p Architectural acoustics
43.58.+z Acoustical measurements and instrumentation

Spatial and temporal fluctuations of acoustic signals propagated over long ocean paths

Ross E. Williams and Chao H. Wei

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1299-1309 (1976); (11 pages) | Cited 1 time

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Acoustic wavefront fluctuations and time‐base distortions were measured on a long linear receiving array with a 2000 ft vertical aperture. The receiving hydrophones were buoyed slightly off the ocean bottom in a roughly uniform distribution over the aperture length. Continuous acoustic transmission up to 17.6 h of a hyperbolic FM signal with a frequency sweep from 350 to 450 Hz was used in each of seven experiments at ranges of 145, 250, 495, and 635 NM to measure signal time‐base distortions. Simultaneously, wavefront fluctuations were determined from changes in arrival time across the aperture of a 10‐msec 400‐Hz pulse from the same projector. Wavefront fluctuations, rotations, and distortions were calculated and compared to signal time‐base distortions measured on a narrow beam directed toward the incoming arrivals. Both RSR (define) and completely refracted path were insonified. In the total wavefront fluctuation, the rotation part was dominant. However, remarkably small standard deviations ranging from 5 to 15 ft over the entire aperture were found for wavefront rotations and distortions. The spectra of the measured time fluctuations and wavefront rotations and distortions reveal common causes, such as tides, overtides, and internal waves.
Subject Classification:[43]30.20.
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92.10.Vz Underwater sound

Correlation of acoustic wavefront and signal time‐base instabilities in the ocean

Ross E. Williams and Chao H. Wei

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1310-1316 (1976); (7 pages)

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Wavefront fluctuations, rotations, and distortions, measured for a particular arrival in the multipath set for long‐range propagation, were cross correlated with acoustic‐signal time‐base distortions for the same arrival. Although the wavefront perturbations contain higher frequency components than for the signal time‐base fluctuations, significant cross correlation amplitudes were found for time and rotation, time and distortion, and distortion and rotation cross correlations. The results demonstrate that common causes, such as tides, overtides, and internal waves, underlie both the temporal and spatial perturbations of the acoustic signal. Although these perturbations were significantly correlated in a high percentage of the tests, the degree of correlation between them was not stable over periods of days or weeks.
Subject Classification:[43]30.20, [43]60.20.
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43.20.+g General linear acoustics
43.60.+d Acoustic signal processing

On the rotational collison number for air at elevated temperatures

H. E. Bass and L. C. Sutherland

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1317-1318 (1976); (2 pages) | Cited 3 times

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A detailed review of the experimental data for the rotational collision number Zrot for air, O2 and N2 has been made to finalize a temperature correction for the absorption due to rotational relaxation for incorporation in a draft standard on air absorption being prepared by the Sl−57 Committee on Propagation.
Subject Classification: [43]35.20, [43]35.35.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Model for predicting the reflection of ultrasonic pulses from a body of known shape

D. M. Johnson

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1319-1323 (1976); (5 pages) | Cited 2 times

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An approximate model for determining the response functions of reflectors of known shape has been used to provide theoretical support for experimental investigations of flaw characterization. The reflection of broad‐band ultrasonic pulses from an object can result in modifications to both the frequency spectrum and phase information in the pulses. These changes are largely controlled by the parameters of the reflector, and relating these factors has been the subject of many experimental investigations. Within the fundamental approximations, the model can readily be applied to any reflector of known shape and provides a simple interpretation of what is physically occurring. It has the advantage that additional experimental factors can be included to determine their effect on the results.
Subject Classification: [43]35.26; [43]20.30; [43]35.80.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.20.+g General linear acoustics

Ultrasonic bounded beam reflection and transmission effects at a liquid/ solid‐plate/liquid interface

Thomas J. Plona, Leslie E. Pitts, and Walter G. Mayer

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1324-1328 (1976); (5 pages) | Cited 10 times

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Schlieren techniques are used to show that bounded beam reflection effects occur at liquid/solid‐plate/liquid (L/SP/L) interfaces which are analogous to the bounded beam reflection effects reported previously at liquid/solid (L/S) interfaces. At L/SP/L interfaces, nongeometric effects are shown to be present in both the reflected and transmitted beams when the incident angle of an ultrasonic beam corresponds to the Lamb angle. In addition, similarities between wave phenomena at L/SP/L interfaces and L/S interfaces are presented which suggest that the description of bounded beam reflection derived by Bertoni and Tamir for a L/S interface can be qualitatively applied to the L/SP/L interface case. This theory is shown to account for the lateral extent to which a leaky Lamb surface wave, excited by mode conversion, propagates.
Subject Classification: [43]35.54; [43]20.40, [43]20.30.
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43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound
43.20.+g General linear acoustics

Mode synthesis technique for dynamic analysis of structures

B. N. Agrawal

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1329-1338 (1976); (10 pages)

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A mode synthesis technique is presented for determining the normal modes, natural frequencies, and responses of three‐dimensional complex structure with flexible joints. Lagrange’s equations are used to develop the equations of motion
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43.40.+s Structural acoustics and vibration
43.20.+g General linear acoustics

Whispering Gallery wave modes on elastic cylinders

J. W. Dickey, G. V. Frisk, and H. Überall

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1339-1346 (1976); (8 pages) | Cited 5 times

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We present an analytic and numerical study of Whispering Gallery‐type surface‐ wave modes on solid elastic cylinders imbedded in a fluid. The complex wave numbers of these waves are obtained for the case of high frequencies (ka≳15), including both their attenuation and dispersion curves for the phase velocities. It is shown that there are two different groups of Whispering Gallery modes whose wave numbers in the limit of infinite frequency or infinite cylinder radius approach the corresponding wave numbers of compressional and shear bulk waves in the cylinder material.
Subject Classification: [43]40.20; [43]30.50; [43]40.55; [43]20.15; [43]35.54.
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43.40.+s Structural acoustics and vibration
92.10.Vz Underwater sound
43.20.+g General linear acoustics
43.35.-c Ultrasonics, quantum acoustics, and physical effects of sound

Transmissibility across clamped circular plates with central loading masses and various rib configurations

J. B. Ochs, J. C. Snowdon, and R. L. Kerlin

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1347-1360 (1976); (14 pages)

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The tranmissibility between the midpoint and the boundary of thin, symmetrically vibrating, circular, aluminum plates of identical dimensions has been determined experimentally in the frequency range 16–2000 Hz. The plates were clamped at their boundaries and loaded symmetrically by concentrated masses or by distributed masses (ribs) of various configurations. The loading masses were always equal to the plate mass, so that their effectiveness in reducing transmissibility could be evaluated as a function of their geometry. Consideration was given to continuous and segmented effectiveness in reducing transmissibility could be evaluated as a function ribs. The transmissibilities across plates loaded centrally by cylindircal masses of small and intentionally large contact areas, and by continuous and segmented circular ribs of small and large diameters, agreed closely with prediction, encouraging belief in the validity of the experimental results obtained for the remaining plates loaded by noncircular ribs, which had theoretically intractable geometries. The transmissibilities across an unloaded plate and a plate plus damping tile also agreed satisfactorily with prediction, even though the transmissibility across the damped plate was calculated from an expression developed for a homogeneous plate with internal damping. The greatest overall reductions in transmissibility were provided by the central loading masses, particularly by the mass having small contact area. By comparison, the reductions provided by the various rib configurations were disappointing; only the performance of the triangular rib and of the small circular rib approached that of the central masses, suggesting use of these ribs when access to the plate center is necessary.
Subject Classification: [43]40.24, [43]40.20.
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43.40.+s Structural acoustics and vibration

Huygens’ principle, radiation conditions, and integral formulas for the scattering of elastic waves

Yih‐Hsing Pao and Vasundara Varatharajulu

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1361-1371 (1976); (11 pages) | Cited 27 times

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Helmholtz‐ and Kirchhoff‐type integral formulas are presented for elastic waves in isotropic and anisotropic solids. The displacement vector field at points interior and exterior to a region bounded by a closed surface is expressed in terms of a volume integral of the body sources and a surface integral of the sources on the closed surface, namely, the traction and the displacement. The kernels of these integrals are the well‐known Green’s displacement dyadic and a third rank Green’s stress tensor. The latter is related to the former by generalized Hooke’s law. From these formulas radiation conditions for both steady‐state and transient elastic waves are established in terms of the traction, displacement, and particle velocity. In the Kirchhoff‐type formula, the retardation in time for the surface and volume sources is made with respect to the travel times for dilatational and shear waves, respectively. This clearly illustrates Huygens’ principle for the two wave fronts of the elastic wave field.
Subject Classification: [43]40.20, [43]40.55; [43]20.15.
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43.40.+s Structural acoustics and vibration
43.20.+g General linear acoustics

Fourth‐order dispersion of free longitudinal waves in a long orthotropic bar of rectangular cross section

Allan J. Zuckerwar

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1372-1378 (1976); (7 pages)

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A perturbation technique described previously is applied to find the dispersion of free longitudinal waves in a long orthotropic bar of rectangular cross section as far as the fourth order of approximation. First the second‐order equations of motion and equations of compatibility are solved to find the second‐order stress distributions; then these are used to derive the exact second‐ and fourth‐order dispersion terms. The second‐ order stresses are related to a homogeneous and a nonhomogeneous potential function. The homogeneous potential function may be described by one of three analytical expressions, depending upon whether the following combination of elastic compliances is less than, greater than, or equal to unity:
A = (s11s33−s13 2) (s22s33−s23 2) / [(s12s33−s13s23) +(1/2) s33s66]2.
Measurements of the first two frequencies of two potassium chloride specimens, having different major orientations, are compared with theoretical predictions; the percent differences are 0.06%, 0.12%, 0.07%, and <0.01%, all of which lie well within the bounds permitted by the uncertainties in the governing parameters.
Subject Classification: [43]40.22, [43]40.20; [43]20.15.
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43.40.+s Structural acoustics and vibration
43.20.+g General linear acoustics

Effect of air flow, panel curvature, and internal pressurization on field‐incidence transmission loss

Leslie R. Koval

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1379-1385 (1976); (7 pages) | Cited 2 times

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In the context of sound transmission through aircraft fuselage panels, equations for the field‐incidence transmission loss (TL) of a single‐walled panel are derived that include the effects of external air flow, panel curvature, and internal fuselage pressurization. These effects are incorporated into the classical equations for the TL of single panels, and the resulting double integral for field‐incidence TL is numerically evaluated for a specific set of parameters. Flow is shown to provide a modest increase in TL that is uniform with frequency up to the critical frequency. The increase is about 2 dB at Mach number M = 0.5, and about 3.5 dB at M = l. Above the critical frequency where TL is damping controlled, the increase can be slightly larger at certain frequencies. Curvature is found to stiffen the panel, thereby increasing the TL at low frequencies, but also to introduce a dip (analogous to the coincidence dip at the critical frequency) at the ’’ring frequency’’ of a full cylinder having the same radius as the panel. This effect, up to now qualitatively understood, can now be quantitatively estimated. Pressurization appears to produce a slight decrease in TL throughout the frequency range, and also slightly shifts the dips at the critical frequency and at the ring frequency.
Subject Classification: [43]50.50, [43]50.45; [43]55.80, [43]55.75.
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43.50.+y Noise: its effects and control
43.55.+p Architectural acoustics

Double eigenvalues of soft circular ducts containing uniform flow and sheared flow

Gus G. Tseo

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1386-1392 (1976); (7 pages)

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Numerical methods to compute double eigenvalues for circular ducts containing uniform and sheared flow are presented. A technique to verify both the maximum exponential decay and the double eigenvalue, impedance, and attenuation in ducts of different sizes are presented and discussed. For well cut‐on modes in a uniform‐flow duct, the impedance velocity by a simple relationship suggested in a previous study. However, in a sheared‐flow duct, optimum impedances are found to have much smaller values than in the uniform‐flow case.
Subject Classification: [43]50.40; [43]20.45, [43]20.40.
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43.50.+y Noise: its effects and control
43.20.+g General linear acoustics

Impedance‐tube calibration of a reverberant room for the measurement of sound power in tones

David Alan Bies and Colin H. Hansen

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1393-1398 (1976); (6 pages) | Cited 1 time

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The use of an impedance tube and horn for the absolute calibration of a 180‐m3 reverberant room for the measurement of sound power in tones is discussed and demonstrated. The results of the calibration procedure are found to compare quite favorably with results obtained using a one‐third‐octave‐band decay method. For a modal overlap index greater than 5, corresponding to frequencies greater than 400 Hz, the difference in the predictions of the two methods is less than 0.8 dB while at a modal overlap index as low as 1.9, corresponding to a frequency of 264 Hz, the difference is less than 1.6 dB. The results of these tests suggest that the one‐third‐octave‐band decay method is quite sufficient for the qualification of a reverberant room with a modal overlap index of 5 or greater for tone‐power measurements. The results of these tests also suggest that any room can be qualified for the measurement of sound power in a tone if it is possible to substitute the mouth of an impedance tube and horn for the source whose sound power is to be measured. The required apparatus is simple and the measurements are easily performed.
Subject Classification: [43]55.65; [43]85.20, [43]85.24.
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43.55.+p Architectural acoustics
43.58.+z Acoustical measurements and instrumentation

Numerical prediction of echograms and of the intelligibility of speech in rooms

François Santon

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1399-1405 (1976); (7 pages) | Cited 2 times

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An improved method for the estimation of speech intelligibility in rooms prior to construction is described which takes into account the directional distribution of the echoes and is based on the concept of received energy being partitioned into useful and disturbing energies. Laboratory experiments are described which substantiate the applicability of the method. The possibility of computing the energy accumulated versus time by specified receivers in a room is discussed broadly; it is shown by numerical example that the image method and the ray method give closely similar results. Numerical computations based on the ray method are compared with experimentally derived energy accumulation curves for two different rooms and are found to agree substantially. Since the computational method also predicts the directional distribution as well as the time accumulation of received sound, it is conjectured that accurate predictions of speech intelligibility taking directionality of echoes into account may be made from architectural plans and from a knowledge of surface absorption coefficients.
Subject Classification: [43]55.20, [43]55.40; [43]70.35.
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43.55.+p Architectural acoustics
43.70.-h Speech production

Deconvolution processing for a nonuniform array

R. N. McDonough

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1406-1411 (1976); (6 pages)

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An ambient acoustic field is assumed to be observed through a delay‐and‐sum beamformer, in conjunction with a line array of non‐uniformly‐spaced sensors. The beamformer output power, as a function of steering direction, is related to the angular power density of the acoustic field through a certain integral equation, with the kernel being the known power response pattern of the array. In this note, we present the results of some computer experiments concerned with solving this integral equation by working directly in the angle domain, rather than in the wave‐number spectral domain. The method is general for any array, but is of interest mainly in the case of a non‐uniformly‐spaced array, to which our examples correspond.
Subject Classification: [43]60.20, [43]60.30; [43]30.82.
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43.60.+d Acoustic signal processing
92.10.Vz Underwater sound

Multidimensional analyses of judgments about traffic noise

Gregory W. Cermak and Peter C. Cornillon

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1412-1420 (1976); (9 pages) | Cited 3 times

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In a laboratory experiment, human subjects were presented pairs of recorded 1‐min traffic sounds. Subjects chose whichever sound of each pair they thought they would rather be exposed to on a regular basis; they also judged the relative dissimilarity of the sounds in each pair. The data were analyzed using multidimensional scaling techniques. The choice data showed that relative aversiveness of the sounds was related mainly to their subjective intensity. The dissimilarity data showed that subjects distinguished sounds on the basis of both subjective intensity and information, independent of intensity, about the source of the sounds. The single physical noise measure most highly correlated with the subjective intensity attribute from both sets of psychological data was Leq, the energy‐equivalent sound level. Several new measures of the shape of the average power spectrum, and of the time‐dependent variability in dBA levels, failed to add appreciably to the predictive power of Leq alone.
Subject Classification: [43]65.75, [43]65.50; [43]50.70, [43]50.50.
Show PACS
42.66.-p Physiological optics
43.50.+y Noise: its effects and control

Temporal auditory summation for pure tones and white noise in the house mouse (Mus musculus)

Günter Ehret

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1421-1427 (1976); (7 pages) | Cited 1 time

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The dependence of the absolute auditory threshold on signal duration was measured by means of behavioral methods in the house mouse (Mus musculus). Twelve frequencies between 1 kHz and 120 kHz and white broad‐band noise were tested while seven pulse durations between 1 and 3000 msec were used. In any case temporal summation follows the function I⋅tb=const until, at a critical duration tc, a constant value is reached where thresholds become independent from signal duration. The critical durations are frequency‐dependent following the general function: tc=p⋅fq (with q<0). This frequency‐dependent nonlinearity could alos be extracted from available data on human hearing. The present results and respective data of the human ear are discussed with reference to a critical‐band‐related summation theory assuming fixed critical bands even for very short signal durations.
Subject Classification: [43]65.68, [43]65.75, [43]65.35; [43]80.50.
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42.66.-p Physiological optics
43.80.-n Bioacoustics

Information extraction from contralateral cues in the detection of signals of uncertain frequency

J. D. Gilliom and W. M. Mills

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1428-1433 (1976); (6 pages) | Cited 2 times

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Observers performed a monaural, yes–no detection task under conditions of signal frequency uncertainty. This frequency uncertainty could be reduced by use of a contralateral cue. The major cue types were a single‐tone cue with the same frequency as the potential detection tone and a three‐frequency cue with the potential signal frequency as the intermediate component. Performance obtained with a single‐tone cue rivaled levels obtained when signal frequency was fixed over a block of trials. Performance with a three‐ frequency cue, requiring extraction of relevant frequency information, produced performance levels only slightly lower than the single‐tone cue condition. Two major conclusions were drawn from the data: (1) The observer, utilizing the single‐tone cue, can nearly eliminate the detrimental effects of signal frequency uncertainty. (2) The ’’hearing out’’ process used to extract relevant frequency information from the three‐frequency cue is nearly complete. The relatively strong support for Ohm’s law obtained from this study may be due, in part, to the level of the auditory system tapped by the present task.
Subject Classification: [43]65.50, [43]65.75, [43]65.54.
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42.66.-p Physiological optics

Temporal masking‐level differences: The effect of mask duration

J. Radford Lakey

J. Acoust. Soc. Am. Volume 59, Issue 6, pp. 1434-1442 (1976); (9 pages) | Cited 2 times

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Psychometric functions were obatained for the interaural conditions NoSo and NoSπ in both forward and backward masking using masks of different durations. In addition, data were collected for the Sm, Sπ and So conditions without an external mask. The slope parameter k and the signal level required for 76% correct detection were computed with a least‐squares technique. The results were that both temporal masking and temporal masking‐level differences (MLDs) increased monotonically with longer mask durations. This mask‐duration effect was more pronounced for forward masking than for backward masking. Without an external mask, the signal was about 3 dB more detectable in the So configuration than in the Sπ configuration, and it was about 4 dB more detectabe in the Sπ configuration than in the Sm configuration. The psychometric functions were generally steeper for the NoSπ condition than for the NoSo condition in forward masking, but not in backward masking. They were also steeper for the Sπ condition than for either the Sm or So conditions without an external mask. The temporal properties of a typical detection model consisting of a filter centered at the stimulus frequency followed by a rectifier and a final ’’leaky’’ integrator were found to explain much of existent temporal masking data. Signal:500Hz, 8 msec; interstimulus interval: 5–10 msec; mask: wide‐band noise; method: two‐interval forced choice.
Subject Classification: [43]65.62, [43]65.58, [43]65.68.
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42.66.-p Physiological optics
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