摘要:

The object of the study was to investigate the sound field existing close to a plate that was free to vibrate and was exposed to an incident‐sound field. Modification of the sound field was sought other than that due to diffraction. This would occur when sound is reradiated under conditions of plate resonance. A square, galvanized, aluminum plate, 12×12×0.020 in., clamped along all four edges, was selected for the study. A simple mode of vibration of the plate, for which a single nodal circle was observed, occurred at a frequency of 74 cps. The amplitude and phase of vibration of the plate relative to progressive plane wave excitation was determined at frequencies in the region of this plate resonance. Simultaneously the acoustic field both adjacent to and distant from the plate's surface was determined. Significant modifications to the incident sound field, as large as 10 dB, were observed. An analysis was developed that, given knowledge of the plate's vibration, accurately predicted this sound‐field modification. [This study was supported in part by the U. S. Air Force.]

ISSN:0001-4966    

DOI:10.1121/1.1939603

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

Sound‐absorption and ‐dispersion measurements have been made using the tube method onCO2‐H2Omixtures over the temperature range of 23°–195°C. A single relaxation time was found to describe adequately both the absorption and dispersion curves. The reciprocal of the relaxation time at each temperature was found to be linearly dependent on the concentration ofH2O. The relaxation time τABwas calculated at each temperature, and τABwas found to increase as the temperature increased. A significant result is that log τABexhibited no minimum value when plotted versusT−13, as has been previously reported by Eucken and Numann, but rather log τABshows a linear decrease versusT−13. The number of collisionsZ10(AB) necessary to deexcite the lowest vibrational mode ofCO2has been calculated from the measured relaxation time and is essentially temperature‐independent. [This work was supported by the U. S. Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1939607

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

The resonant frequency and the mass load of vibrating full‐scale propellers are calculated from experimental data of scaled‐down models. The method is described, and data for a variety of different propellers are presented in tabulated form.

ISSN:0001-4966    

DOI:10.1121/1.1939615

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

In estimating file effectiveness of a multimount isolation system, it is necessary to know the mobility or impedance characteristics of the machine, the mounts, and the foundation structure. As a first step in the study of estimating mount effectiveness, this paper considers the mobility characteristics of a machine idealized as a rigid body of simple geometrical shape having an arbitrary number of mounting points. Equations are presented for calculating the point and transfer mobilities at the mounting points of such idealized machines. Mobility measurements on a steel rectangular parallelopiped (an idealized model of a machine with approximately a block shape) of dimensions ratio 3×5×7 are compared with theoretical values. Several recommendations are made relevant to mobility‐coefficient calculation and to the problem of mount‐effectiveness estimation.

ISSN:0001-4966    

DOI:10.1121/1.1939617

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

The case of surface‐wave propagation in a homogeneous layer embedded in a homogeneous medium has been reported in the literature. On the other hand, if the layer is inhomogeneous, the problem is considerably more complicated. In fact, only for a very few special cases does an exact solution exist. In this study, the inhomogeneity is introduced by allowing the sound velocity to have a layer depth dependence. A method is presented here that demonstrates the manner in which the variation of sound velocity affects the dispersive characteristics of the medium. The structure described is essentially an acoustic waveguide and normal‐mode techniques are used to produce a mathematical model. The resulting modified Sturm‐Liouville boundary‐value problem is converted into a Fredholm integral equation through the use of the Green's‐function technique. The kernel of this integral is quantized in such a fashion as to yield the relationship between the phase velocity of the surface wave and the layer depth. Dispersion curves for velocity profiles that could occur in the ocean are presented in the paper.

ISSN:0001-4966    

DOI:10.1121/1.1939628

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP

摘要:

If an arbitrary signal is transmitted from a fixed point in the ocean to a fixed receiver, the received signal will be a highly modified, or distorted, version of the transmitted signal. The modification of the “input” into the “output” can be considered analogous to that performed by an electrical network, or filter. It is shown that this is not merely an analogy but a legitimate generalization, i.e., that the electric filter is merely a simple instance of the same general process. This generalization is used to discuss the following problems: (a) analysis of the ocean filter; (b) synthesis of a prescribed filter; (c) measurement of a filter by impulse response and by frequency‐response methods; (d) correlation between two similar filters [see A. Parvulescu, “M.E.S.S. Processing,” J. Acoust. Soc. Am.33, 1674(A) (1961)]; (e) inversion of a given filter. [Hudson Laboratories, Columbia University Informal Doc. No. 73. Work supported by the U. S. Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1939630

出版商:Acoustical Society of America    

年代:1965

数据来源: AIP