摘要:

A technique is described in which the ultrasonic time delay between successive echoes in an echo train is determined by phase comparison of the echoes with a coherent continuous signal. Corrections for phase shift of an echo upon reflection from the face of a transducer and for diffraction effects are discussed. The velocity of sound at 1 MHz in distilled water from 23° to 75°C has been measured with this technique. Measurements of time delay are accurate to 20 ppm while the over‐all accuracy is 127 ppm or ±0.20 m/sec. Excellent agreement with values in the literature is found.

ISSN:0001-4966    

DOI:10.1121/1.1911597

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This paper is concerned with the investigation of the effect of microstructure in the solution of several problems of wave propagation. The propagation of plane waves in a micropolar elastic half‐space and their reflections from a stress free flat surface are studied. It has been found that in a micropolar elastic solid, four waves can exist traveling at four distinct speeds, two of which disappear below a critical frequency dependent upon the character of the medium. Reflection laws and amplitude ratios are presented for three specific problems.

ISSN:0001-4966    

DOI:10.1121/1.1911598

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Longitudinal wave propagation in a nonhomogeneous semi‐infinite elastic rod is considered. The non‐homogeneity may be due to the axial variation of Young's modulus or of density or of both. An arbitrary time‐dependent stress is applied at the end,x= 0, of the rod. The normal stress as a function of position and time is obtained using the theory of the propagating surfaces of discontinuity by expanding the stress as a Taylor series about the time of arrival of the wavefront. The coefficients of the Taylor expansion are obtained as solutions of linear ordinary differential equations with variable coefficients. For the case where the Young's modulusE(x) varies as (1 +ax)2a, it is shown that the stress at the wavefront varies as (1 +ax)α, whereaand α are constants.

ISSN:0001-4966    

DOI:10.1121/1.1911599

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Masking of a short tone (located inside or on the skirts of a narrow noise band or masked by wide‐band noise) demonstrates interactions between sets of onset and offset effects and their relation to temporal development of auditory frequency contours.

ISSN:0001-4966    

DOI:10.1121/1.1911600

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Jitter and asynchrony discrimination are considered as special cases of the discrimination of temporal irregularities within auditory pulse trains. Variation in the number of nonjittered intervals permits spanning the range between the discrimination of a single temporal discontinuity (the asynchrony or gap test) and the discrimination of temporal modification to each interval (the jitter test). At high pulse frequencies, the discrimination of temporal irregularities is determined primarily by the number of jittered intervals. Jitter thresholds are approximately inversely proportional with the fourth root of the number of jittered intervals.

ISSN:0001-4966    

DOI:10.1121/1.1911601

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Additional pertinent references are pointed out in this Letter. Some of the results obtained by Durvasula are compared with values recently published in the open literature.

ISSN:0001-4966    

DOI:10.1121/1.1911602

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

In speech studies where articulatory activity is of prime interest and where no excitation through vocal‐cord vibration is available or desirable, one wants to examine the response of the vocal tract to an external excitation source. This note describes a method to generate such a speechlike signal from the incident and reflected waves caused by excitation of the vocal tract at the lips. The result approximates the signal that would have been generated by periodically exciting the same tract configuration at the glottis, provided that the tract is not completely constructed within its interior.

ISSN:0001-4966    

DOI:10.1121/1.1911603

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The velocity dispersion of the first‐order longitudinal mode of two isotropic 24STaluminum rods of square and circular cross sections has been investigated and the results compared with the experimental results of Morse and the theory of Nigro. It is shown that the theory of Nigro does not adequately account for the lowest‐order velocity dispersion in a square rod. Morse observed that the velocity dispersion curves of a square and of a circular rod coincide as a function of diameter‐to‐wavelength ratio, provided the equivalent diameter of the square rod is assumed to be 1.13 times the thickness of the rod. An equivalent diameter of 1.155 times the thickness of the square rod is shown to be superior for the present experimental results, as it ensures almost full coincidence of the two dispersion curves over the full range of diameter‐to‐wavelength ratio.

ISSN:0001-4966    

DOI:10.1121/1.1911605

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Recently published pure‐water round‐speed data are compared to earlier Naval Research Laboratory data with a caveat to their application to existing sea‐water sound‐speed tables.

ISSN:0001-4966    

DOI:10.1121/1.1911606

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The mean‐square static‐pressure distribution induced by statistically roughened duct walls on a supersonic stream passing through its interior is analyzed in this Letter. It is found that the maximum value of the mean‐square static pressure occurs on the duct walls and that this value is inversely proportional to(M∞2 − 1)12.

ISSN:0001-4966    

DOI:10.1121/1.1911607

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP