摘要:

The correlation properties of noise fields when considered as a random superposition of elementary sources are derived as an extension of Rice's work on the shot effect [S. O. Rice, Bell System Tech. J.34, 282 (1944);24, 46 (1945)]. Next a formalism is derived which calculates the correlation properties of the response of a continuous, linear system when subject to an applied noise field. The requirements for solution are a knowledge of the impulse response of the system and the correlation function of the source. The latter may be obtained experimentally or from calculation.

ISSN:0001-4966    

DOI:10.1121/1.1908228

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

The dispersion of a rectangular pulse with many cycles of carrier frequency propagated along an acoustic wave guide of rectangular cross section has been observed experimentally. The main signal is propagated with the group velocity and is observed to separate from the initial and final transient portions which travel with the greater, free medium velocity. In the dispersion process, the beating of the initial transient with the main signal causes fluctuations in the envelope of the carrier which compare favorably with the mathematical formulation given. This experiment serves, essentially, as a calibration of the wave guide so that it can be used qualitatively as a type of analog computer to predict the effects of similar dispersion on the transmission of pulses of other shapes that are not amenable to actual computation.

ISSN:0001-4966    

DOI:10.1121/1.1908230

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

A method is developed for easily determining the directivity pattern in an arbitrary distance from the emitter from measured instantaneous values of the field in other distance. Numerical computation is facilitated by the tables put together in this paper.

ISSN:0001-4966    

DOI:10.1121/1.1908232

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

A method is proposed for determining the traveling and standing components of an arbitrary scalar wave field from the measured instantaneous values of the field on the surface of two spheres surrounding the emitter.

ISSN:0001-4966    

DOI:10.1121/1.1908234

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Theshock spectrumfor an acceleration impulse applied to an electronic equipment or other component is a measure of severity of mechanical shock in terms of possible peak response at each frequency within the component structure. It is commonly measured by a reed gauge, which is intended to simulate the possible resonant characteristics of the internal structure. The reed gauge is bulky, however, and provides data at a limited number of frequencies.The shock spectrum computer operates on an accelerometer signal, either direct or recorded, and permits measurement of as many points in the spectrum as desired. It is a device which solves the differential equation of a simple undamped resonant mechanical appendage for any applied impulse of acceleration to yield the response. In the present version, the response is made available as an output signal which is applied to a commercial cathode‐ray oscilloscope. Peak accelerations and their time of occurance may be obtained readily from the oscilloscope display. The computer can be tuned to any frequency up to 2000 cps. Control circuitry is used to damp the computer shortly after each impulse and to undamp it immediately before the next so that the impulse under study can be applied repeatedly from a recirculating loop of magnetic tape. Shock spectra obtained from the computer and oscilloscope display are used as a measure of the severity of shocks experienced by electronic apparatus and as a basis for deriving shock specifications for use in design approval tests.

ISSN:0001-4966    

DOI:10.1121/1.1908235

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Data on the absorption of upholstered theater chairs as measured during the construction of a 496‐seat auditorium and a 738‐seat auditorium are presented. These data obtained on the seats after placement in each auditorium indicate a much lower absorption per seat over the entire audio‐frequency band than has previously been reported. Before the seats were installed in the 496‐seat auditorium, 1080 ft2of Axminster carpet were laid on the floor of this room, and the absorption characteristics of this full scale sample were determined. These data are also reported in this paper.

ISSN:0001-4966    

DOI:10.1121/1.1908184

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Difference‐limens for the discrimination of intermittence were obtained at ten interruption rates of random noise between 1 and 320 cps. The duty cycle of the intermittent noise was 0.5 and the sound pressure level was 75 db. Data from four listeners give average deviations from the standard frequency (ΔF) of 0.02 to 9.74 cps. The graph relating ΔFandFfrom 1 to 320 cps shows ΔFto be a monotonically increasing function ofF. When the data are plotted with logarithmic coordinates, two functions are revealed, suggesting a change in the method of frequency discrimination at about 5 cps. This change appears due to the listener's ability to count the noise bursts from 1 to 5 cps, but not above about 5 cps. The relationship between 5 and 320 cps may be described by a parabolic function of the formy = axb. Below 5 cps, the form of the relationship cannot be determined from the data available. The relative difference‐limen, ΔF/F, lies between 0.008 and 0.03, and graphic integration of 1/ΔFyields 560 just noticeable differences in the range studied. These data show difference‐limens for flutter that are smaller than those previously reported.

ISSN:0001-4966    

DOI:10.1121/1.1908186

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Two electronic devices for automatically extracting the first three formant frequencies from continuous speech are described. Both devices are designed to yield three continuous dc output voltages whose magnitudes, as functions of time, represent the formant frequencies of the input speech. The principles of operation and the design features of both devices are discussed, and typical examples of the operation of each are presented.

ISSN:0001-4966    

DOI:10.1121/1.1908188

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

A procedure for evaluating the operation of two electronic formant extractors is described and results of the evaluation are given. The formant extractors are designed to yield electrical outputs representing the formant frequencies of continuous input speech. These outputs are compared in a prescribed manner to formant data derived from sound spectrograms. The results show that the more reliable extractor of the two follows the first formant of vowel sounds in speech within ±150 cps greater than 93% of the time; it follows the second formant within ±200 cps greater than 91% of the time. The first and second formant outputs of the same extractor are simultaneously within the above tolerances greater than 85% of the time.

ISSN:0001-4966    

DOI:10.1121/1.1908190

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

If one in the study of transmission of sound into a moving medium allows flow speeds larger than twice that of sound, the analysis indicates at least formally the existence of two critical angles between which total reflection occurs. A discussion of the corresponding behavior of the angle of refraction and the reflection coefficient is presented.

ISSN:0001-4966    

DOI:10.1121/1.1908192

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP