摘要:

The establishment of the Riverbank Acoustical Laboratories in Geneva, Illinois, had its origin in the interest of Colonel George Fabyan in an acoustic device purportedly described by Francis Bacon in a secret cipher embodied in the printed First Folio (1623) of the works of William Shakespeare, and the resulting acquaintance of Fabyan with Professor Wallace Sabine of Harvard University.

ISSN:0001-4966    

DOI:10.1121/1.1912347

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Sound‐transmission‐loss tests were conducted using steel‐stud drywall partitions with a single layer of12‐in.wallboard on each side to study the effect on acoustical performance due to the physical properties of cavity fill. These tests also compared the results using mineral wool and glass fiber and using studs of different widths. All tests were conducted in accordance with ASTM E90‐66T. The transmission loss and sound‐transmission class (STC) were found to be related directly to the thickness of fibrous absorbing material when used in the full cross area of the stud cavities. The increase in STC due to increasing thickness of the cavity fill is not a linear relationship, since the first inch has the greatest effect. When the absorbing material is placed in less than the full cross area of the stud cavities, the gain in acoustical performance is governed by the volume of the absorption material. The low‐density glass fiber performed as well as high‐density mineral wool except in the middle portion of the curve, where the transmission loss averaged 1 dB less. Increasing the stud size increases the transmission loss. This gain is limited to the lower frequencies when cavity absorption is present.

ISSN:0001-4966    

DOI:10.1121/1.1912348

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Stray admittance and lead effects may be eliminated from the calibration of a condenser microphone by use of three‐terminal measurement techniques. Modern ac‐bridge null‐balance methods applied to the measurement of electrical transfer impedance between two condenser microphones, cavity coupled for reciprocity calibration, result in a significantly higher accuracy than attainable by currently used deflection‐comparison methods, and yield phase in addition to amplitude information. Using the bridge described reduces the uncertainty arising from all electrical measurements in the reciprocity determination of condenser microphone pressure response to less than ±0.006 dB from 400 Hz to 600 Hz, ±0.004 dB from 600 Hz to 1000 Hz, and ±0.01 dB at 10 kHz.

ISSN:0001-4966    

DOI:10.1121/1.1912349

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The frequency response of a closed flue pipe as a function of blowing pressure is examined. It is hypothesized that the turbulence level in the air jet is the controlling factor in fixing the frequency of oscillation. Modifications are made in the flue pipe to reduce turbulence in order to test the hypothesis. Consequences of the turbulence‐driven oscillation with regard to the use of such oscillators as temperature sensors are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1912350

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

In this paper, the likelihood ratio detector for zero‐mean complex Gaussian vector signals in zero‐mean complex Gaussian vector noise is considered. The receiving apparatus is assumed to be spatially distributed, and only a single frequency of interest is treated. By simultaneous diagonalization of the signal and noise spatial covariance matrices, saySandN, a canonical form is found for the familiar detector appropriate to this problem. Using this canonical form, a number of special cases follow easily. First, for small signals such that all eigenvalues ofSN−1are less than 1, we obtain the approximate detector. We then obtain the usual matched filter and threshold for the plane‐wave signal case, and a generalization to the case of a signal which is a superposition of plane waves. Finally, for signals such that the smallest nonzero eigenvalue ofSN−1is greater than 1, we obtain the asymptotic detector. Few of the results presented are new, but it is hoped that their derivation in a unified way from the canonical detector will be illuminating. Our aim is to combine some standard communication‐theory techniques with some standard matrix‐theory results, in the setting of the acoustic array data‐processing problem.

ISSN:0001-4966    

DOI:10.1121/1.1912351

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912352

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A schlieren system has been used to produce motion pictures of acoustic wave interactions with cylinders. Details of the system are described.

ISSN:0001-4966    

DOI:10.1121/1.1912353

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912357

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912362

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912367

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP