摘要:

Investigators have studied the absorption of sound energy in toluene from 30 kc to 200 Mc in an effort to determine the causes of the excess absorption. The results to date have raised many puzzling questions. For example, Verma and Yeager (private communication) have reported a resonance peak at 50 kc, the existence of which is quite difficult to explain. R. T. Beyer reports a relaxation peak at 150 kc, the mechanism of which is not clear. We have made ultrasonic absorption measurements in toluene using the reverberation method and the pulse method over a frequency range from 150 kc (overlapping Beyer's [J. Acoust. Soc. Am.27, 1 (1955)] frequencies) to 55 Mc and a temperature range from 6° to 44°C. The high‐frequency attenuation is studied as a function of temperature, and it is found that the temperature dependence is different from that reported by G. S. Verma [J. Chem. Phys.18, 1352 (1950)]. The results in the kilocycle region show that the absorption per wavelength has a resonance type peak at approximately 210 kc independent of temperature with a magnitude that increases with increase in temperature. TheQof this loss mechanism is about the same as theQof the resonance type loss reported by Verma and Yeager in the 50‐kc region. The position and magnitude of the peak at 210 kc is unaffected by the introduction of ethyl alcohol as an impurity up to concentrations of 10% by volume.

ISSN:0001-4966    

DOI:10.1121/1.1909178

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The use of light diffraction for the measurement of the sound‐pressure amplitude and the waveform of ultrasonic waves has been extended to the case of ultrasonic pulses. The method has been applied to transducer calibration in water at 5 Mc for pulses of 3 to 12 μsec duration, and compared with calibration by means of continuous waves. The distortion of the waveform in ultrasonic pulses of finite amplitude is demonstrated by measurements of the transducer voltage vs light intensity in the first diffraction orders. All measurements made with continuous waves and with pulses give approximately identical results.

ISSN:0001-4966    

DOI:10.1121/1.1928107

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

An optical method is used to measure the energy ratio of reflected and incident ultrasonic waves at a liquid‐solid interface. The ultrasonic velocities in the solid are calculated from the angles of maximum reflection in the liquid.

ISSN:0001-4966    

DOI:10.1121/1.1928108

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Sound absorption and velocity measurements in fluorine at 28° and 102°C indicate vibrational relaxation times of 20.7 and 10.7 μsec for these two temperatures, respectively. The measurements were made inside a glass tube 1.73 cm in diameter using progressive waves. These results when combined with earlier results in the other halogens indicate certain changes which improve the accuracy of the Slawsky, Schwartz, and Herzfeld theory.

ISSN:0001-4966    

DOI:10.1121/1.1928109

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The vibration of circular plates with a large initial tension (or compression) is studied for the case of (a) simply supported and (b) clamped edges. The basic equation used is that of the Poisson‐Kirchhoff theory. Numerical results are given.

ISSN:0001-4966    

DOI:10.1121/1.1928110

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The load impedance of a generator or the radiation impedance of a transducer can be controlled by a second active generator coupled to the first generator by a transmission line. The primary control variables are the relative magnitude and phase of the signals in each generator. A load impedance of any magnitude and phase, including negative resistance, can be obtained. The second generator is used as an active reflector and absorber. The theory is applicable to the case where the generators are underwater sound transducers and the line is a water‐filled tube.

ISSN:0001-4966    

DOI:10.1121/1.1928111

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The essential function of the optimum detector is that of applying linear mean‐square regression process to the output of the array and measuring the power in the residues thus formed. The elements required for instrumentation of the detector are deduced and numerical examples relating to specific array configurations are presented. At low frequencies the directivity pattern of the optimum detector is superdirective. There is strong evidence that this directivity pattern is the one having maximum directivity index.

ISSN:0001-4966    

DOI:10.1121/1.1928112

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

In the frequency region below 1 kc, the effect of velocity inhomogeneities on acoustic propagation in the ocean will be negligible. In this frequency region, fluctuations in travel time and ray direction will be caused by scattering from rough boundaries. In this paper, the effect of boundary scattering on the resolution of ray paths is investigated. Using a simplified model of the process, a rough estimate of the spatial line broadening of a low‐frequency ray in the ocean is obtained.

ISSN:0001-4966    

DOI:10.1121/1.1928113

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

The characteristics of a piston‐type transducer that must withstand varying hydrostatic pressures can be improved by mechanically preloading the assembled transducer prior to operation and by carefully matching the axial compliances of the individual elements. A simple analysis and some tests of an experimental preloaded transducer are described, and the particular advantages of conical disk springs as transducer isolators are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1928115

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP

摘要:

Acoustical pulses of variable length and repetition rate are generated by an electronic system composed of instruments which are commercially available, except for a gate unit. The system is designed to permit acoustic transmission and reflection experiments in a controlled water medium within the confines of a laboratory‐size wooden tank. Pulses of sine wave between 60 kc and 1 Mc are used. An acoustical source constructed of a barium‐titanate spherical cap generates an acoustical pressure field as high as 2.1×104μbar (86.7 dbre1 μbar at 1 m) at 230 kc at a distance of 1 m which is sensed by miniature hydrophones with lead titanate‐zirconate disk elements as small as 0.063 by 0.009 in. The ceramic is enclosed by metal to overcome problems encountered previously with waterproof coatings incapable of keeping water from the ceramic for long periods of immersion. Pressure sensitivity of the probe hydrophone with preamplifier (49.6‐db gain) is 10.3×10−6v/μbar (−99.8 dbre1 v/μbar) at 230 kc.

ISSN:0001-4966    

DOI:10.1121/1.1928116

出版商:Acoustical Society of America    

年代:1962

数据来源: AIP