摘要:

Measurements have been carried through about the angular distribution of sound traveling in a reverberation chamber in which a certain amount of absorbing material is installed. It was measured during the decay phase of sound. Two methods were used, the first one with a directional sound source and a nondirectional microphone, the second one using a nondirectional source and a directional microphone developed in the PTB. In the latter case, the differences of angular distribution of sound, impinging on the absorbing sample, could be shown for two different states of diffuseness accomplished in the reververation chamber by installing different numbers of diffusing elements in the room. The angular distributions were investigated at frequencies of 1.2, and 4 kc.

ISSN:0001-4966    

DOI:10.1121/1.1908542

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The 3200‐seat Congress Hall in Jerusalem, Israel was completed in the spring of 1960 after a construction period of some 10 years. The original primary design goal was to provide a place for large assemblies the most important of which was the biennial meeting of the World Zionist Congress. During construction, the repeated use of the partially completed “unroofed” structure for out door concerts led to the reconsideration of the original design goals to give primary emphasis to music. The hall now has become the Jerusalem home of the Israeli Philharmonic while still serving its function for congresses and other uses. This paper traces the development of the acoustical design goals as well as discusses the important acoustical design features, the results of measurements made in the completed hall, and the reactions of musicians who have played in the hall.

ISSN:0001-4966    

DOI:10.1121/1.1908544

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The probability distribution of pressure amplitudes in a room is studied theoretically and experimentally. A point source is assumed to emit a Poisson sequence of pulses. The method of cumulant generating functions is used to obtain the distribution of response in the direct field, the reverberant field, and the transition region. In the direct field, the source statistics are reproduced. For sufficiently reverberant spaces, the reverberant field tends to normality independently of the source distribution. For sufficiently short pulses (or short autocorrelation time of the source) the direct and reverberant fields are statistically independent. When these simplifying conditions are not met, we indicate how the results may be generalized. Implications for calculations of random fatigue and component malfunction are discussed briefly.

ISSN:0001-4966    

DOI:10.1121/1.1908546

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

It was established that the loudness of a 1000‐cps pure tone in the presence of random noise is given byψ = k(In − I0n), whereIis the pure tone intensity andI0the threshold intensity of the pure tone in the presence of masking noise. The exponentnis approximately 0.27, and the value ofkdepends on the choice of units. This relation also holds when the only masking noise present is the physiological noise generated in the ears, and it thus describes the conventional loudness function.

ISSN:0001-4966    

DOI:10.1121/1.1908548

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

By use of a high‐power, corona type loudspeaker we have been able to demonstrate behavioral and endocrine responses of laboratory rodents to measured high sound‐pressure levels at the frequencies at which their hearing is most sensitive, namely, 10 to 40 kc. The corona type loudspeaker behaves in the fashion predicted by the theoretical analysis reviewed in this paper. It is limited by extremely low efficiency (2.5%) and high production of ozone. At high frequencies it is limited by the volume of the corona, and at low frequencies by the failure of the quasi‐adiabatic condition within the corona. Despite these limitations its performance has not been equaled by other types of loudspeakers; it is a unique tool for studying the responses of laboratory rodents to sound fields.

ISSN:0001-4966    

DOI:10.1121/1.1908550

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A method of directly evaluating the impulse response of a reciprocal electroacoustic transducer is presented. The method is essentially the time‐domain analog of the conventional (frequency‐domain) reciprocity method. The transient response of a coupled pair of identical transducers is used to compute the impulse response of either of the pair. A numerical method of obtaining solution is presented and is shown to be equivalent to the numerical solution of a real convolution integral equation. First, an approximate solution for one member of the pair of identical transducers is obtained. Then, a more precise solution is generated by minimizing the squared error between the actual response of the coupled pair and the one obtained by convolving the approximate impulse response with itself.The method was tried on two pairs of condenser microphones, the microphones within each pair being very nearly identical. A pair of Western Electric 640‐AA microphones were tested with the grids both on and off, and a pair of Bruel and Kjaer type 4131 microphones were tested with the grids on an off and with grids equivalent to those on the W.E. 640‐AA both on and off.Two unsatisfactory solutions resulted when W.E. 640‐AA grids were used on the transducers. Three solutions were satisfactory, even though each contained slight negative drift for large values of time. One solution contained no appreciable error in its entire time course.

ISSN:0001-4966    

DOI:10.1121/1.1908552

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Relative resonant displacement of bar magnetostrictors as a function of polarization at atmospheric stress and at a compressional, axial stress of 230 atm is measured. Laminated bars of nickel and 2V‐permendur are driven at frequencies both at and well below the resonant frequency of the bars, about 23 kc. Measurements of theQand the reversible permeability enable one to compare the magnetostrictive constants and the coupling at the two stress levels for both materials.The resonant displacement was found to change only slightly upon application of the compressive stress, for polarizing fields up to 100 oe. The compressive stress increased the maximum coupling for permendur by about 10%, the stress decreased the maximum coupling for nickel by about 10%.

ISSN:0001-4966    

DOI:10.1121/1.1908554

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Procedures are described for reducing the speech wave to a specification in terms of the time‐varying vocal‐tract resonances and source characteristics. The basic method, which has been called analysis by synthesis, involves the comparison of speech spectra with a series of spectra that are synthesized within the analyzer. Each comparison spectrum is generated according to a set of rules based on an acoustical theory of speech production. The result of the analysis of each input spectrum is a set of parameters that describes the synthesized spectrum providing the best match. In one version of the method convergence, towards the best match is controlled by the experimenter; in another version convergence to a match is accomplished automatically without the intervention of the experimenter. All the operations have been programmed on a general‐purpose digital computer and have been applied to the analysis of vowels and some consonants. The advantages of the analysis techniques are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1908556

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The damping constants of vowel formants, as expressed in the half‐power bandwidths, have been studied from the reports of several investigators. The accuracies of methods of measurement used have been estimated through application of the same methods to an electrical analog of the vocal tract. Two new sets of measurements are presented, one on spectrograms of real speech, the other making use of an artificial larynx, applied to real subjects. It is concluded that, while wide individual variations occur, the average bandwidths for male voices probably lie in the lower range of those which have been reported.

ISSN:0001-4966    

DOI:10.1121/1.1908558

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Results of an investigation of diffraction of light passing through a distorted finite amplitude ultrasonic wave are given. A method is developed and used to determine the second harmonic component of the distorted wave at various distances from the transducer while maintaining a constant local fundamental component. It is shown that the observed discrete diffraction order intensities (wide light beam) and the observed continuous light distribution (narrow light beam) are in good agreement with theoretically predicted values. Measurements were made at 3.0 Mc in water with approximately23 atmlocal fundamental pressure amplitude.

ISSN:0001-4966    

DOI:10.1121/1.1908560

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP