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, finite-amplitude wave (pump) which travels in the (0,0) mode. The other is a high frequency, small-signal wave which travels in the (1,0) mode. A formula for the modulation, and accompanying suppression, of the small-signal 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 small-signal 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 cross-section 70 mm x 38 mm. Waveforms of the frequency modulated small-signal wave were recorded, the suppression of the small-signal 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