1979-02-01

APPLICATION OF ACOUSTIC INTENSITY MEASUREMENT TO ENGINE NOISE EVALUATION 790502

ABSTRACT

This paper is concerned with the application to engine noise analysis of a cross-spectral method of measuring acoustic intensity recently developed at the General Motors Research Laboratories. The effectiveness and practicality of the approach is demonstrated in a series of tests conducted with a naturally-aspirated, two-stroke V-8 diesel engine. A rapid space-time averaging technique for determining the sound power radiated by sections of different engine components is demonstrated, as well as detailed mappings of noise emission by the engine surface. Noise-source ranking of engine components is performed based on intensity measurements made at the engine surface, and the total engine sound power is determined by summing these individual contributions. The sound power determined at the engine surface in this way is compared with estimates of engine sound power based on acoustic intensity measurements made both over a spherical surface and a set of planar surfaces enclosing the engine. Agreement to within 0.1 dB and 0.5 dB respectively is obtained. This close agreement is a good indication of the overall accuracy and effectiveness of the acoustic intensity method.

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