摘要:

The propagation of plane waves in a prestressed elastic solid with incremental elastic coefficients possessing orthotropic symmetry is discussed. Two types of plane waves, called quasi‐Pand quasi‐Swaves, are shown to exist. An expression for the group velocity of these waves is obtained. The velocities of quasi‐Pand quasi‐Swaves are found to depend on the angle of propagation. The reflection coefficients of these waves incident at the free surface of a prestressed elastic half‐space are derived. Critical reflection of quasi‐Pand quasi‐Swaves has been discussed. It is found that while quasi‐Swaves always have critical reflection, quasi‐Pwaves can have critical reflection only if incremental elastic coefficients satisfy a certain condition.

ISSN:0001-4966    

DOI:10.1121/1.391155

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

For the calculation of wave scattering by targets of complex shape it is suggested that the Helmholtz integral equation be solved in configuration space directly. Expansion in terms of spherical or spheroidal waves is thus avoided. The method is tested by calculating the scattering of acoustic waves by rigid spheroids of various shapes and orientations. The method appears to be particularly well suited to the intermediate wavelength regime where the wavelength is comparable to the dimension of the target.

ISSN:0001-4966    

DOI:10.1121/1.391156

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

An exact representation which involves single (as opposed to double) integrals is established for the time‐average power output generated by individual modes of normal surface velocity on a simply supported and baffled rectangular panel; fluid loading is not taken into account. The representation enables analytical estimates to be found in the short wavelength range and provides details hitherto unresolved by numerical analysis.

ISSN:0001-4966    

DOI:10.1121/1.391157

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

ABR and behavioral thresholds were estimated as a function of stimulus duration for three normal and two hearing‐impaired subjects. Stimuli were 2000‐Hz tone bursts with 0.5‐ms rise/fall times and durations ranging from 1 to 256 or 512 ms. For both groups of subjects, ABR thresholds were independent of stimulus duration. Normal subjects showed greater improvement in behavioral thresholds as a function of duration than did subjects with hearing losses. Thus, it appeared that ABR and behavioral thresholds were affected differently by changes in stimulus duration and that the magnitude of these differences could depend upon the presence of hearing loss. These data indicate that temporal integration may be one factor which makes comparisons between ABR and behavioral thresholds complicated. In the present study, the magnitude of hearing loss, measured by the ABR, would have been underestimated if normal behavioral thresholds for short‐duration stimuli were used as the reference.

ISSN:0001-4966    

DOI:10.1121/1.391158

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

In a recent publication [Symons, J. Acoust. Soc. Am.74, 851–860 (1983)] theoretical performance capabilities of the optimum filter for maximization of SNR and of a suboptimum approximation were compared to the conventional matched filter in the case of signals masked by surface reverberation. Some representative theoretical spectra are presented in order to give insight into the effects of the filters in a reverberation environment.

ISSN:0001-4966    

DOI:10.1121/1.391159

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

It is shown that the adiabatic approximation usually presented in the literature for acoustic normal mode propagation in a range‐dependent ocean has serious limitations and breaks down at rather short ranges. This is because the approximation does not account properly for the phase of the modes. A rigorous, uniformly valid asymptotic expansion is presented which provides a solution with greatly improved range of validity.

ISSN:0001-4966    

DOI:10.1121/1.391160

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Experimental observations indicate that when a bounded beam of ultrasound is incident upon a plane liquid–solid interface at the Rayleigh angle there is a significant amount of radiation backscattered in the direction of the incident wave. Recently this phenomenon was explained in terms of a backward propagating leaky Rayleigh wave. We show here that in a pulse‐echo mode of operation thefowardpropagating leaky Rayleigh wave is likely to a give a much larger contribution to the signal received at the transducer than the correspondingbackwardwave.

ISSN:0001-4966    

DOI:10.1121/1.391161

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

We consider the phenomenon of back reflection of a beam of ultrasound from a liquid–solid interface. We show that the magnitude of the back reflection depends critically upon the profile of the incident beam. The beam profile is first related to the excitation field at the plane of the transducer. Different beams are considered by changing the field at the transducer. We show that a purely Gaussian profile gives no back reflection. Other beam profiles with less severe decay away from the beam center can produce an effect of the same order as observed experimentally. We present an example of such a beam.

ISSN:0001-4966    

DOI:10.1121/1.391162

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

摘要:

Acoustical terms are often misused—a typical example being the use of ‘‘intensity’’ instead of ‘‘sound pressure level.’’ In the last year and in 7 out of 11 issues of JASA, this fundamental mistake appeared in titles of papers. Authors and reviewers should pay more attention so the quality of papers published in ourJournaldo not contain such a fundamental error.

ISSN:0001-4966    

DOI:10.1121/1.391117

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.391120

出版商:Acoustical Society of America    

年代:1984

数据来源: AIP