摘要:

The use of absolute‐admittance measurements has been limited in the past to the determination of parameters of relatively high‐Qresonators. By allowing only one major assumption in the analysis of the resonator, new equations are developed which consider the mechanical loss to be a first‐order effect. On the basis of extensive numerical calculations of resonator characteristics in which no approximations were made, the errors of both the conventional relationships and the new equations are made evident. It is found that these new equations materially extend the usefulness of this method of measurement to include systems for which the mechanicalQis lower than the capacitance ratio. For the extreme case exemplified by a barium titanate ceramic resonator in air, the conventional calculation method introduces errors of approximately fifty percent in some of the crystal parameters as compared to errors of one percent for the new equations. The improvement is less significant in the determination of the parameters of underwater sound transducers.

ISSN:0001-4966    

DOI:10.1121/1.1907351

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

Increasing use is being made of cylindrical barium titanate tubes as underwater acoustic transducers. An exact derivation is given for the low‐frequency acoustic sensitivity of such tubes for a variety of boundary and polarization conditions.

ISSN:0001-4966    

DOI:10.1121/1.1907352

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

By means of a modification of the pistonphone, a technique has been developed to obtain the response of a capacitance type vibration pickup probe using the reciprocity calibration of a condenser microphone as a reference. The raised, center portion of a circular piston, driven by a barium titanate cylinder, projects into one end of a cavity, the shelf of the piston being located outside of the enclosure. A calibrated condenser microphone coupled to the other end of the cavity responds to the sound pressure developed by the piston. The output of an annular capacitance type vibration pickup, which detects the motion of the piston shelf, is compared with the generated microphone voltage. With the microphone removed from the cavity, the output of a capacitance probe located adjacent to the top surface of the piston is compared with that of the annular pickup. The probe response is computed from these measurements and the microphone response.From considerations of checks by independent methods, an accuracy of about 0.5 db is indicated from 100 to 10 000 cps. Using a sensitive probe, vibration amplitudes as small as 10−9cm have been measured with a comparable degree of accuracy.

ISSN:0001-4966    

DOI:10.1121/1.1907353

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

A theoretical investigation is made of the response of an elastic half‐space to a vertical impulse at the surface. Dissipative properties are incorporated in the medium and dissipation coefficients λ′, μ′ varying as thenth power of the frequency are assumed. These lead to dispersion and absorption. The response may be described by components of the three distinct types,P‐,S‐, andR‐. Each is observed at the surface as a train of waves culminating in a characteristic phase about the instantsr/α,r/β, andr/γ, respectively, where α, β, and γ are the velocities of propagation ofP‐,S‐, andR‐ waves in nondissipative media andris the focal range. These phases are discussed in detail; their “amplitude” and “span” are defined and the variations of each of these quantities and their ratios withr, density ρ and the material constants are derived. A schematic determination of λ and μ (the elastic constants),n, λ′, and μ′ from experimental data is outlined.

ISSN:0001-4966    

DOI:10.1121/1.1907354

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

A simple method of expressing the logarithmic measure of physical quantities is proposed, which is generally applicable to all quantities and avoids the use and misuse of the term decibel.Editor's note.—It is believed that discussion and critical thought on this subject should be encouraged. and it is to this end that this Letter is published. The Editors do not necessarily concur with the views expressed.The definition of the decibel and related units will be studied during the forthcoming revision of American Standard Acoustical Terminology Z24.1‐1951 by Sectional Committee Z24. Suggestions (especially in the form of preferred wordings of definitions) are welcomed; address proposals to Chairman of Writing Group Z24.W‐5, Robert W. Young. U.S. Navy Electronics Laboratory, San Diego 52, California.

ISSN:0001-4966    

DOI:10.1121/1.1907355

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1907356

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

Sound power output of a plate type transducer is obtained by measuring the reaction force on the transducer.

ISSN:0001-4966    

DOI:10.1121/1.1907357

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

It is shown that the general treatment by van de Hulst of the dispersion and absorption of sound arising from mechanical‐electromagnetic coupling in conducting fluids immersed in magnetic fields applies directly to conducting elastic solids.

ISSN:0001-4966    

DOI:10.1121/1.1907358

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1907359

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP