摘要:

The noise emitted by motor vehicles varies in intensity as a function of speed and operating mode. For highway operation, the relative significance of the various vehicle noise sources is similarly dependent. Bounds of operational noise levels for representative automobiles are presented. The relevance of current test methods to typical vehicle operation is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1981583

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

A spinning mode synthesizer has been developed to study the propagation of complex higher order modes in cylindrical ducts. This device has been shown (“The Design, Development, and Use of a Spinning Mode Synthesizer,” M. J. Oslac, and J. M. Seiner, Proc. Purdue Noise Conf.) to be very useful in studying the behavior of spinning waves which are believed to be the principle component of the noise generated by fans, compressors, and jet engines. In this investigation, the spinning mode synthesizer was coupled to a 12‐in.‐diam cylindrical duct 8 ft long, which was in turn coupled to an 8‐ft‐long, 18‐in.‐diam cylindrical duct having an anechoic termination. Single higher‐order modes were then propagated down the infinite duct having at its center an abrupt cross‐sectional change. Radial, axial, and circumferential measurements were made in both the 12 and 18‐in. ducts. Transmission, reflection, and generation of modes at the discontinuity are compared with a mathematical model. [This research is being conducted under a NASA grant.]

ISSN:0001-4966    

DOI:10.1121/1.1981592

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

In a church of typical rectangular plan and modified “A”‐shaped cross section, acoustical data were taken with the main aisle and chancel carpeted and later with gypsum board covering the carpet. The measurements were made with the sanctuary occupied and unoccupied. The acoustical parameters compared are reverberation time, loudness, and articulation index. The study indicates that the absorption coefficients normally used for an audience and the published coefficients for carpets are not valid for rooms with this general configuration.

ISSN:0001-4966    

DOI:10.1121/1.1981599

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The T.I.D. of 13 May 1964, discussed by Theme appears to have had unusually high amplitude and would seem well suited for further investigation into its possible extension into the southern hemisphere as well as the possible presence of a simultaneous northbound wave. Withf‐plot data, supported by tabulated hourly values, as well as, in some cases, the actual ionegram, we have found some evidence for an extension of the wave into the southern hemisphere with a phase change of 180° in accordance with Thome's predictions. Preliminary investigations into a northbound wave seem to reveal a disturbance traveling at different velocity from the southbound T.I.D.

ISSN:0001-4966    

DOI:10.1121/1.1981604

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP

摘要:

The laboratory measurements of Evans and Bazley, Pohlmann, Harris, and Tempest and Harris were first chosen from all those available in the literature for the attenuation of sound in air. They form an authoritative international consensus. The attenuation was then calculated using the fundamental method of Kneser as well as the empirical methods of Harris and Committee A‐21 of the Society of Automotive Engineers. Comparison of calculated and measured values show gross deviations in going from method to method, and from all methods to measurement, in some part of the range of frequency, humidity, and temperature of interest to problems of community noise. An extension of the fundamental method of Kneser to include the vibrational relaxation of nitrogen as well as oxygen is found to be in good agreement with the measurements. Directions of research to improve these methods are recommended.

ISSN:0001-4966    

DOI:10.1121/1.1981609

出版商:Acoustical Society of America    

年代:1972

数据来源: AIP