摘要:

A group of hydrophone elements uniformly and closely spaced along a straight line is used to measure the angle of arrival of sound waves. By sampling the outputs of these elements rapidly and in succession, one simulates single hydrophone moving relative to the sound waves. The signal measured at the output has a frequency given by the Doppler equationf=f0(1 +α cosθ), wheref0is the frequency of the sound in the water, α is the ratio of the scanning speed to the speed of sound, and θ is the bearing angle desired. The theoretical results expected along with the experimental measurements which confirm the theory and a description of the equipment used are included.It was found that the scanned system simulates almost exactly a single moving point hydrophone, and the Doppler equation was found to hold. Pure tones and narrow‐band noise signals are shifted in frequency. The angular resolution was found to be equal to the ratio of the wavelength of the sound to the component of the hydrophone length normal to the direction of sound propagation.

ISSN:0001-4966    

DOI:10.1121/1.1928117

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The problems associated with determining the angular distribution of continuous and discrete noise sources by means of a linear additive array are discussed. A spatial frequency analysis shows that an array acts as a low‐pass filter in the spatial frequency domain and hence cannot distinguish between spatial‐noise distributions whose spatial spectra differ outside the spatial bandwidth of the array. It is shown that smoothing due to side‐lobe response results in a large reduction in the ability of an array to measure accurately peaks in the angular distribution.

ISSN:0001-4966    

DOI:10.1121/1.1928118

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Equations are derived to describe an underwater sound transducer consisting of an acoustical transmission line coupled to a low‐pass electrical transmission line. If the two transmission lines have the same phase velocity, the energy of a wave is transferred cyclically from one line to the other as a function of line length; a reversible transducer with a lowQ, high efficiency, and essentially constant resistive impedance is thereby achieved. Theory and four proposed designs are described.

ISSN:0001-4966    

DOI:10.1121/1.1928119

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The sound fields resulting from a plane wave incident on a spherical elastic shell are found. Both the internal and external fields due to the shell are considered and compared with well‐known results. The Rayleigh limit is discussed, and it is found that the external field is similar to that produced by a rigid sphere but with more complicated coefficients. The internal field is of a complicated nature but reasonable to consider for numerical computation. The sound fields for a hemispherical shell mounted on a rigid medium are obtained by the image method. Numerical results for the sound intensity at the center of the hemisphere are presented for various elastic materials.

ISSN:0001-4966    

DOI:10.1121/1.1928120

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The ability of subjects to judge the distance of the source of an unfamiliar sound was studied. It was found that distance judgments on the first trial were unrelated to actual distance. With further trials valid distance judgments became possible.

ISSN:0001-4966    

DOI:10.1121/1.1928121

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

It is suggested that the hearing threshold shift found in underwater subjects indicates that the human ear is basically a velocity‐sensitive device.

ISSN:0001-4966    

DOI:10.1121/1.1928122

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The vibrational relaxation in nitrogen and oxygen, both pure and with admixtures, has been measured with a high‐pressure Kundt's tube. Pure nitrogen relaxes atf0/pof 1 cps/atm, at 203°C; oxygen at 90 cps/sec at 50°C.

ISSN:0001-4966    

DOI:10.1121/1.1928125

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Bulk viscosity and ultrasonic absorption coefficients for carbon tetrachloride and chloroform at 20°C, 1 atm, have been recalculated in order to correct an earlier result which has been modified more recent work. The changes increase the vibrational relaxation contribution to the absorption by a factor of order unity, while the structural contributions, resulting from relaxation of the distribution of free volume, are left unchanged. New values for tetrachloride and chloroform, respectively, are: for bulk viscosity 0.2729 and 0.2934 poise; for 2α/ν2, the intensity absorption divided by the sound frequency squared, 8.84×10−15and 7.88×10−15sec2/cm. This represents an improvement, which is not very significant, in the agreement with experiment.

ISSN:0001-4966    

DOI:10.1121/1.1928126

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The method of ultrasonic interferometer has often been used in measuring the sound velocity in liquids. The accuracy of this method, however, is not an excellent. The present method will give a good advance in the accuracy and in the upper limit of the applicable frequencies. The writer was able to detect 0.2 μ of the movement in the acoustical path of particular distances. A frequency of 15 Mc was used.

ISSN:0001-4966    

DOI:10.1121/1.1928127

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

A summary is given of past observations of microbaroms, atmospheric pressure oscillations that have periods near 5 sec, and it is shown how the generation of these oscillations is explained by Nanda's theory of the origin of micro eisms.

ISSN:0001-4966    

DOI:10.1121/1.1928128

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP