摘要:

Most analyses of loudspeaker performances are based primarily on the consideration of details of the electromechanical coupling. This approach has proved too inadequate to handle loudspeaker radiation problems. An attempt has been made to set up a general expression relating the free field sound pressure at a remote point to the electrical signal applied to the loudspeaker terminals. This relation in the form of an integral equation is solved exactly for a loudspeaker of circular shape. By means of the solution of the integral equation it appears possible to apply to this problem methods analogous to circuit analysis techniques which represent the transfer function of the system in terms of its characteristic points in the complex frequency plane.

ISSN:0001-4966    

DOI:10.1121/1.1907283

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

The freedom from humidity and temperature limitations have made ferroelectric ceramics valuable type of transducer for phonograph pickups (originally designed for 78 rpm records). Two groove sizes now indicate the use of dual styli. A pickup structure is described in which dual styli are used hack‐to‐back on one lever. A mechanism provided on the bottom of the pickup whereby the stylus assembly can be turned over to present the proper stylus to the record. This structure imposes no dynamical limitations on the performance of the pickup, as the additional mass required for the second stylus is only a small percentage of the total mass, and no additional stiffness constraints are imposed on the system.Reasonably flat characteristics have been obtained. In one commercial model a sensitivity of over one‐half volt is achieved on microgroove records, with a frequency range to 10 000 cps with a tracking force of 6 grams for microgroove and 9 grams for standard‐groove records.

ISSN:0001-4966    

DOI:10.1121/1.1907281

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

Simple whistles have been constructed that produce sound by the escape of a vortex from the open end of a tube. The whistle operates equally well on either air or water.When the frequency that is produced by the passage of either air or water is plotted against the volume rate of fluid flow, it is found that the frequency depends almost linearly on the rate of flow and that the number of cycles produced by the flow of a unit volume of air is nearly the same as that produced by the flow of a unit volume of water. Measurements have been made relating the frequency of the sound produced to different pressures of air applied to the whistle.

ISSN:0001-4966    

DOI:10.1121/1.1907282

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

The dependence of a jet‐tone orifice numbertf/(Δp/ρ)12on Reynolds number[ρt(Δp/ρ)12]/μis shown for thin sharp‐edged circular orifices whose thickness and diameter both vary from approximately18to38in, wheretis thickness of orifice plate;f, frequency; Δp, pressure difference across orifice; ρ density; and μ, viscosity of gas. Each jet‐tone, in general, is composed of harmonics (fundamental and over‐tones) as well as subharmonics (tones whose frequencies are less than the fundamental). The subharmonics are relatively unsteady in amplitude compared to the harmonics and may at times have a greater amplitude. The jet‐tones at low Reynolds numbers appear relatively free of noise background. In general, as Reynolds number is increased to high values the noise background at first engulfs the subharmonics, then the harmonics. The fundamental is the last to remain, finally disappearing the noise background.

ISSN:0001-4966    

DOI:10.1121/1.1907284

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

1. The flow in two dimensions of an oscillating incompressible fluid near a circular cylinder with its axis normal to the direction of oscillation, is studied theoretically and experimentally. Starting from Navier‐Stoke's differential equations the method of successive approximations has been used in order to get approximative solutions, when the appropriate boundary conditions are applied. The zeroth approximation gives the modified field of oscillation near the cylinder as a function of the viscosity. The first approximation also gives a stationary flow, which is found from the solution of an ordinary linear differential equation of 4th order.2. Experiments have been carried out in air in a Kundt's tube. The velocities in the plane normal to the axis of the cylinder have been found by photographing smoke particles in air. The experimental and theoretical results agree fairly well. Comparison with corresponding data obtained by Schlichting is also made.SomeGfunctions, derived from Hankel functions which have been used in the theoretical solutions, have been tabulated to 6 digits.

ISSN:0001-4966    

DOI:10.1121/1.1907285

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

The mean force acting on a rigid sphere placed in a progressive spherical sound field has been obtained by integration of the individual contributions from the velocity potential and particle velocity acting on each element of the sphere's surface. Motion of the sphere under the action of the first order pressure variations in the sound field has been taken into account. The radiation force has been expressed as an infinite series of inverse powers of the source distance, each term of which is multiplied by an infinite power series in terms of sphere radius. At very large distances from the source the radiation force obeys an inverse square law of repulsion. As the source of the field is approached, the repulsion decreases to zero and then becomes a force of attraction. The extent of this region of attraction is determined both by the frequency of the sound field and by the size of the detecting sphere; lower frequencies and smaller spheres both extend the region. Even when allowance is made for an inverse square law, the attractions may be many times greater than the repulsions in the same sound field.

ISSN:0001-4966    

DOI:10.1121/1.1907286

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

The theory of the previous paper has been verified by a series of quantitative experiments. Several hollow glass spheres (0.228 to 3.029 cm radius) were suspended in turn by a fine glass fiber in the sound field in air; the deflection of each was measured at known frequencies (300 to 7000 cps) and amplitudes (0 to 1400 d/cm2) of the sound field. Care was taken to protect the sphere from any gas streaming to or from the source and to insure that the field was accurately spherical. All measurements were made under such conditions that the sound field was substantially sinusoidal. Good agreement was obtained between theory and experiment within the range of the variables investigated. In the region where radiation forces of attraction existed, this agreement was always within a few percent, even though the magnitude of the forces changed by a factor of 100 or even 1000 to 1 in a single experiment. In the region of repulsion, measurements could not be made with any great accuracy, but even so the agreement here was within the limits of experimental error.

ISSN:0001-4966    

DOI:10.1121/1.1907287

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

The dissipative effects of viscosity and heat conductivity are studied here in connection with the flow of a compressible fluid in a parallel channel or tube. Two kinds of waves or pulses are considered and the distortion from the customary square wave calculated. An observer at a fixed point on the channel and two traveling with the wave are seen to give information as to the order of decay or dissipation of the wave with increasing time.

ISSN:0001-4966    

DOI:10.1121/1.1907288

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

By combining the results of Kirchhoff and Knudsen, the effect of viscosity and heat conduction on a spherical sound pulse are found. A rectangular pulse becomes Gaussian, its peak moves with sound speed, its width increases proportionally to √t, and its amplitude decreases proportionally tox−1, wherexdenotes radial distance from the origin. This behavior is exactly the same as that of a pulse in one dimension, except for an extra factor of 1/xwhich accounts for the spherical spreading.

ISSN:0001-4966    

DOI:10.1121/1.1907289

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP

摘要:

As very intense sound waves propagate, the wave‐shape changes into one of saw‐tooth form producing abrupt rises in pressure called shock fronts. This waveform distortion into so‐called repeated shock waves is caused by the nonlinearity of the medium. The objective of this study has been to obtain experimental facts relative to the propagation of repeated shock waves in tubes and to compare these with existing theory. An intense sound source was constructed and appropriately coupled to a series of measuring tubes. Observations were made on the velocity and attenuation of fully developed shock waves for a variety of gases, for pressure amplitudes as great as 0.25 atmosphere, and for a fundamental frequency range of from 400 to 1200 cycles per second.The data were compared with previous theoretical work, particularly that of Professor Rudnick. Agreement was found in the general aspects of the theory; the exact magnitude of the effect remains to be explained. This discrepancy between theory and experiment may be resolved by considering in greater detail the absorptive processes involved.

ISSN:0001-4966    

DOI:10.1121/1.1907290

出版商:Acoustical Society of America    

年代:1954

数据来源: AIP