摘要:

The absorption and scattering of a plane wave of sound by an infinitely long circular cylinder, whose axis is perpendicular to the direction of propagation of the wave, are calculated. The surface of the cylinder is assumed to have a known normal acoustic impedance. The calculations take account of diffraction effects. Absorption measurements were made on long cylinders placed in a reverberation room, where the incident wave directions are at all angles to the axes of the cylinders, and were compared with the calculated values. In order to make the comparison, The reverberation room statistics appropriate for cylinders (which are different from the statistics for flat patches of absorbent material) are developed and applied. The theory predicts, and measurements confirm, that absorbent cylinders can have coefficients of absorption greater than unity. Fairly good agreement between the calculated and measured coefficients is found. The reverberation room statistics appropriate for spherical absorbers are also developed, although no measurements were made on spheres.

ISSN:0001-4966    

DOI:10.1121/1.1916331

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

A small acoustical tube is described, which is suitable for measuring absorption coefficients of acoustical materials over a limited frequency range. This instrument is useful for checking the acoustical characteristics of materials after they have been applied to the walls of theaters, studio review rooms, and other auditoriums.

ISSN:0001-4966    

DOI:10.1121/1.1916332

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916333

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

In the design of mechanical filters whose function is, to prevent the transmission of vibration from one structure to another, it is necessary to know the impedances of the structures between which the filter is to be connected. In many of the cases which arise in practice, the impedance may be estimated from a knowledge of the driving‐point impedance of an infinite plate. An expression is obtained for the impedance of an infinite plate of constant thickness when connection is made to the plate at a single point. The impedance may be written in the form 8ρh2v, where ρ is the density,hthe thickness of the plate, andva velocity approximately equal to the velocity of shear waves in the material. It is shown that the driving‐point impedance is equal, except for a constant factor, to the impedance of a mass equal to the mass of a disk cut from the plate whose radius is the mean proportional of the thickness and the wave‐length which corresponds tov. The results are exemplified by applying them to the case of a steel plate.

ISSN:0001-4966    

DOI:10.1121/1.1916334

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916335

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916337

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916338

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

This paper is intended to start inquiry into the question: Do chords, considered as fusedklangeffects, have individual “tone colors” analogous to thetimbresof different instruments? As a first step, only the qualities of two‐tone intervals are considered. Sine waves representing simple tones (without overtones) are superposed, by graphic means, so as to produce characteristic composite wave patterns for each of the commonly used intervals. Study of the resultant curves would seem to suggest that: (1) Each interval has a characteristic composite sound‐wave‐pattern. (2) The length of the composite wave pattern is equal to a number of cycles of the lower frequency expressed by its number in the interval ratio. (3) The composite wave patterns of dissonant intervals are longer and more complex than those of consonant intervals. (4) Comparison of the curves of an interval and its inversion shows little outward resemblance. (5) Intervals may be grouped together into “families,” according to the lengths of the composite wave patterns. These groupings differ somewhat from those usually recognized by harmonic theory. (6) An interval may be said to have a “frequency” equal to the number of complete cycles per second of the composite wave pattern characteristic of that interval. The lower interval frequencies are more dissonant. (7) A study of the configuration of the composite wave patterns shows how it is still possible for the ear to identify the component pitches in a given interval. (8) There seems to be graphic evidence of the physical existence, in the composite wave patterns, of frequencies corresponding to the difference tones.

ISSN:0001-4966    

DOI:10.1121/1.1916339

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP

摘要:

This report describes a system intended primarily for high quality sound recording on film. It was privately developed by a German physicist, Dr. Carlheinz Becker, of Thansay über Rosenheim. The system employs well‐known means in some respects, but has the important advantage of giving excellent 3‐channel reproduction of great dynamic range and low noise level using a sound track of total width of only 2.65 millimeters.

ISSN:0001-4966    

DOI:10.1121/1.2142324

出版商:Acoustical Society of America    

年代:1946

数据来源: AIP