摘要:

Hydroacoustic signals caused by the summer 1970 French atmospheric explosions are interpreted in terms of propagation between source and receiver through the deed sound channel. The observed signal is similar to the classical slope‐generatedTphase of shallow‐focus ocean margin earthquakes.

ISSN:0001-4966    

DOI:10.1121/1.1912556

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Farfield transmitting response, free‐field sensitivity, and directivity patterns of both small and large (up to 18 ft in one dimension) underwater audiofrequency transducers have been obtained by direct measurement made in the nearfield with a special hydrophone, the NRL 33‐ft ×33‐ft nearfield calibration array (NFCA). Some of the measured results are compared to the results determined by the classical farfield measurements, except where only computed results were feasible. The calibrating array hydrophone consists of 2500 acoustic sensors in a square array of 8‐in. spacings. These acoustic sensors were amplitude shaded according to the distribution advanced by Mr. W. James Trott [J. Acoust. Soc. Amer.36, 1557–1568 (1964)]. Applicable theory and fabrication design data for the special hydrophone are briefly noted.

ISSN:0001-4966    

DOI:10.1121/1.1912557

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The expression that results from raising the pattern function of a symmetric linear array of equispaced point sources to some integer power greater than unity can be identified as the pattern function of a larger symmetric linear array of point sources with the same spacing. In this manner, one may determine a distribution of source strengths for a large array so that its pattern displays characteristic features of a smaller array, such as fewer sidelobes. In the case where the original pattern function is raised to an even power, the sidelobes of the pattern of the associated larger array all have the same phase.

ISSN:0001-4966    

DOI:10.1121/1.1912558

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Burgers' equation is a nonlinear acoustical wave equation which approximately governs the propagation of finite‐amplitude waves with dissipation and spreading losses. A new solution is derived for a spherically diverging sinusoidal waveform. By means of this solution, the amplitudes of the harmonic levels above the third can be more readily estimated than by successive approximation.

ISSN:0001-4966    

DOI:10.1121/1.1912559

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The attenuation of the impulsive sound from a pistol is measured in an anechoic chamber by means of miniature condenser microphones. The shock waves were measured 1.3–4.7 m from the source and exhibited peak levels from 147 to 159 dBre2 × 10−5N/m2. The duration of the positive phase was about 200 μsec. The peak pressurePas a function of the distancesis described by the relationP/P0 = (s0/s)1.17±0.03. Limited variations in relative humidity, temperature, and atmospheric pressure did not significantly influence the exponent of this relation.

ISSN:0001-4966    

DOI:10.1121/1.1912560

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A solution has been found for the acoustic power extracted from the near potential field of a subsonic rotor, by interaction with a nonuniform inlet flow. The analysis is based on Lighthill's aerodynamic sound equation, modified to allow for a uniform mean flow, and is restricted to low‐solidity rotors (lifting line approximation). Within this approximation, the power at blade‐passing frequency is compared with that radiated from unsteady blade forces arising from the same nonuniform inlet flow. The comparison shows that more power may be radiated by the potential field interaction at high subsonic Math numbers, if the rotor disk loading is high.

ISSN:0001-4966    

DOI:10.1121/1.1912561

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912562

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP