Nonlinear interaction of two noncollinear sound waves in a rectangular waveguide
Abstract
This report examines the nonlinear interaction (in air) of two noncollinear sound waves in a rectangular waveguide. One of the waves is a low frequency, finiteamplitude wave (pump) which travels in the (0,0) mode. The other is a high frequency, smallsignal wave which travels in the (1,0) mode. A formula for the modulation, and accompanying suppression, of the smallsignal wave by the pump is derived. The modulation depends on the angle of intersection, theta, of the two waves because: (1) only the velocity component u cos theta, of the pump convects the smallsignal wave; and (2) the two waves have different group velocities (geometric dispersion). Experiments to examine both collinear and noncollinear interaction were performed in a 6.4 m long rectangular waveguide of inside crosssection 70 mm x 38 mm. Waveforms of the frequency modulated smallsignal wave were recorded, the suppression of the smallsignal primary was measured, and the cyclical variation (in space) of the sum and difference frequency wave amplitudes was examined. Theoretical predictions were generally confirmed.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 June 1984
 Bibcode:
 1984STIN...8434666T
 Keywords:

 Amplitudes;
 High Frequencies;
 Rectangular Waveguides;
 Sound Waves;
 Wave Interaction;
 Wave Propagation;
 Low Frequencies;
 Nonlinear Systems;
 Rectangular Beams;
 Rectangular Planforms;
 Traveling Waves;
 Communications and Radar