Unidirectional acoustic probe based on the particle velocity gradient

Abstract

This paper presents the foundations of a unidirectional acoustic probe based on the particle velocity gradient. Highly directional characteristics play a key role in reducing the influence of undesired acoustic sources. These characteristics can be achieved by using multiple acoustic sensors in a spatial gradient arrangement. Two particle velocity sensors possessing the figure eight directivity pattern were used in a first-order gradient configuration to yield a unidirectional probe that can reject most excitations originating from both sides and the rear. The effects of key parameters are thoroughly discussed, and the proposed theory is validated in practice.

Quantitative Analysis Method and Correction Algorithm Based on Directivity Beam Pattern for Mismatches between Sensitive Units of Acoustic Dyadic Sensors

“…The directivity index of an ADS with only one uniaxial acoustic particle velocity gradient channel ( ) is 6.99 dB [ 15 ], which is nearly 1 dB (about 16.7%) higher than that of a complete triaxial acoustic vector sensor with four channels ( ). Moreover, as long as a uniaxial particle velocity gradient channel is added to the triaxial acoustic vector sensor, the maximum directivity index of the acoustic sensor can be increased from 6.0 dB to 9.5 dB [ 16 ] (about 58.3%).…”

“…Calculate the difference between this ratio and the ratio of the ideal cosine squared beam pattern, which is similar to Equation (15).…”

“…For the measured beam pattern shown in Figure 12, the BW I VG actual is equal to 0.0779. Substituting 0.0779 into Equation (15), the magnitude of amplitude mismatch µ can be estimated as 1.048 (0.41 dB).…”