摘要:

Abstract not available.

ISSN:0001-4966    

DOI:10.1121/1.422690

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.423118

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.422691

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet athttp://www.uspto.gov.

ISSN:0001-4966    

DOI:10.1121/1.422692

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Theoretical and experimental results are presented for the force law between two rigid, parallel plates due to the radiation pressure of broadband acoustic noise. The noise is in the band of 5–15 kHz and has an intensity of 133 dB(re: 10−12 W/m2). Excellent quantitative agreement is shown between theory and experiment. These results constitute an acousticanalogfor the Casimir effect, which is the force experienced by two closely spaced uncharged conducting plates due to the quantum electromagnetic zero-point field. In contrast to this case, however, band-limited noise can cause the force to beattractiveorrepulsiveas a function of separation between the plates.

ISSN:0001-4966    

DOI:10.1121/1.422744

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Two experiments were carried out to determine how manipulating the compression ratio and release time of a single-band wide dynamic range hearing aid affects sound quality. In experiment I, compression ratio was varied over the range from linear to 10:1 (low compression threshold, attack time=5 ms, release time=200 ms). In experiment II, compression ratios of 1.5, 2, and 3:1 were combined with release times of 60, 200, and 1000 ms (attack time=5 ms). Twenty listeners with sensorineural hearing loss rated the clarity, pleasantness, background noise, loudness, and the overall impression of speech-in-noise (Ventilation, Apartment, Cafeteria) processed through a compression hearing aid. Results revealed that increasing compression ratio caused decreases in ratings on all scales. Increasing release time caused ratings of pleasantness to increase, and ratings of background noise and loudness to decrease. At the 3:1 compression ratio, increasing the release time caused increases in ratings of clarity, pleasantness, and overall impression, and a decrease in background noise. Significant correlations were found between scales. Regression analysis revealed that the contributions of the scales of clarity, pleasantness, background noise, and loudness to the prediction of overall impression differed as a function of the competing noise condition.

ISSN:0001-4966    

DOI:10.1121/1.422745

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Classical Lamb waves in an homogeneous, isotropic linearly elastic plate are reconsidered. The displacement components are obtained in terms of thickness motions superimposed on a membrane carrier wave which defines the propagation along the plate. The carrier wave can be any solution of the reduced wave equation for a membrane. The analysis of the thickness motions results in the usual Rayleigh–Lamb frequency equation. A number of special cases for the carrier wave are considered.

ISSN:0001-4966    

DOI:10.1121/1.422746

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

The feasibility of exciting a localized X-wave pulse from a finite aperture is addressed. Also, the possibility of using a finite-time excitation of a dynamic aperture to generate a finite-energy approximation to an X-wave pulse is explored. The analysis is carried out by using a Gaussian time window to time limit the infinite X-wave initial excitation. Huygens’ construction is used to calculate the amplitude of the radiated wave field away from the finite-time source. The decay rate of the peak of the X wave is compared to that of a quasi-monochromatic signal. It is shown that the finite-time X-wave propagates to much farther distances without significant decay. Furthermore, the decay pattern of the radiated X-wave pulse is derived for a source consisting of an array of concentric annular sections. The decay behavior of the radiated pulse is similar to that of an X-wave launched from a finite-time aperture. This confirms the fact that time windowing the infinite energy X-wave excitation is a viable scheme for constructing finite apertures. A discussion of the diffraction limit of the X-wave pulse is also provided.

ISSN:0001-4966    

DOI:10.1121/1.422747

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

In this paper analytic formulas are developed for the ray path and travel time of a ray propagating in a wavy fiber–epoxy composite material and calculate them for rays initiating at various points with wave normals of differing directions. The arrival times observed by using various combinations of pointlike sources and pointlike detectors are found in good agreement with those predicted by the theory of geometrical acoustics.

ISSN:0001-4966    

DOI:10.1121/1.422748

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP

摘要:

Acoustical data transmission through the wall of drill pipes is considered. Drill pipes are known to behave like bandpass filters; the position of the pass bands can be determined analytically. This work extends the frequency domain drill pipe models presented by Barnes and Kirkwood [J. Acoust. Soc. Am.51, 1606–1608 (1972)], and more recently by Drumheller [J. Acoust. Soc. Am.85, 1048–1064 (1989)]. The approach discussed in this paper has the advantage that it yields explicit expressions for the fine structure of the drill pipe’s frequency response in the pass bands. It furthermore allows the effect of energy dissipation and pipe segment length variations to be included in the model. The emphasis of the paper, however, lies on the time domain modeling of the drill pipe. The propagation of sound energy pulses through its wall, and the effect of multiple reflections and/or transmissions during this propagation, are described using a Markov chain. Explicit expressions result for the expected duration of an energy pulse’s trip from one end of the drill pipe to the other, depending upon the number of drill pipe segments and the transmission coefficient at the tool-joints connecting them. The results are applicable to any situation where sound or energy transmission through a cascade of acoustic components occurs.

ISSN:0001-4966    

DOI:10.1121/1.422749

出版商:Acoustical Society of America    

年代:1998

数据来源: AIP