The Suppression of Sound by Sound of Higher Frequency.
Abstract
The purpose of this research was to study the suppression of one sound by another sound of higher frequency. More specifically, the planar propagation in air of a finite amplitude tone (the pump) and a smaller amplitude tone (the weak signal) of lower frequency was investigated both theoretically and experimentally. Suppression is caused by an acoustic modulation process. The amount of suppression depends qualitatively on whether the pump frequency is lower than the weak signal frequency (Case I) or vice versa (Case II). Case I has been previously studied and large suppression of the weak signal has been obtained. Even through preliminary analytical work indicated that little suppression is possible in Case II, the present research was undertaken to determine the amount of suppression possible. Various exact and approximate preshock solutions were reviewed in the time domain (Earnshaw solution) and frequency domain (Fenlon solution). Postshock solutions were based on weak shock theory whichwas implemented in a computer algorithm, corrections for attenuation and dispersion were incorported. Predictions thus obtained were compared to experimental results. The experiments, performed in a 30 m progressive wave tube, were restricted to Case II. The agreement between experimental results and theoretical predictions was excellent. In particular the experiments confirmed the theoretical prediction that little suppression of the weak signal is obtained for Case II either before or after shock formation. The sidebands in both cases form around the high frequency and its harmonics.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1977
- Accession Number
- ADA040008
Entities
People
- William L. Willshire Jr
Organizations
- University of Texas at Austin