Collinear interaction of noise with a finite‐amplitude tone
作者:
Don A. Webster,
David T. Blackstock,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1978)
卷期:
Volume 63,
issue 3
页码: 687-693
ISSN:0001-4966
年代: 1978
DOI:10.1121/1.381795
出版商: Acoustical Society of America
数据来源: AIP
摘要:
The interaction between a low‐level band of noise and a finite‐amplitude tone has been measured in air in a plane progressive wave tube. Noise bands generally 1–3 octaves wide with center frequencies in the range 0.7–1.2 kHz were used. At the source the tone SPL was in the range 140–151 dB (re20 μPa); the frequency was either within the noise band or somewhat above. The data show the following. When the tone is absent, the noise propagates as a small‐signal wave. When the tone is turned on, however, a strong modulation takes place. After a propagation distance of only a few meters, not necessarily beyond the point of shock formation for the tone, the noise spectrum extends many octaves above the original noise band and, moreover, becomes nearly flat. The energy required to extend the noise apparently comes from the tone and its harmonics, not the original noise band. Theoretical predictions have also been obtained. A computer algorithm based on the Earnshaw solution, with corrections for tube wall absorption added, was used. The input waveform of the noise was constructed from the measured source power spectrum, the components of which were assigned random phase. The computed results agree well with the experimental data.
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