Optimal Spectra for Parametric Arrays, with Tables.
TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
Pagination or Media Count:
The use of more than two spectral components in the primary signal of a parametric end-fire array is considered. Equations are developed for the spectra of N components which maximize the farfield SPL in the shock free case. Effects of the variation of attenuation with frequency are shown to have a considerable influence on the shape of the optimal spectra. For the case of attenuation proportional to f sq., the optimal spectra are functions only of the downshift ratio, R, and the number of components, N, and are not functions of the absolute value of the frequencies. The optimal spectra and waveforms for several sets of R and N values are shown. It is found that a 3 dB increase over a two-component primary can be obtained with three or four components for a wide range of downshift ratios. At extremely high primary frequency powers, an increased tendency toward shock formation may negate this gain. Beamwidths were found to be essentially unaffected.
- Acoustic Detection and Detectors