Determination of the pressure equivalent noise signal of vector sensors in a hybrid array

Abstract

The advent of particle velocity sensors as a viable addition to traditional pressure-based sensors in acoustics has fueled considerable research into the additional capabilities they might bring. Previous thesis work performed at NPS successfully demonstrated a working acoustic beamformer using a hybrid array comprised of a single conventional omnidirectional microphone and two 3D Microflown Ultimate Sound Probes in an anechoic chamber. These Microflown sensors are vector sensors. They have integrated directionality through the inclusion of three orthogonal particle velocity sensors with a microphone. Unfortunately, the signals of the particle velocity sensors obtained outside in a light, gusting wind were unusable due to broadband noise. Since the fundamental limit to detecting quiet targets depends on the noise floor, the aim of this thesis was to perform an in situ measurement of the pressure equivalent noise floor of all sensors in the array and to minimize the wind noise. Noise levels measured in an anechoic chamber were 915 dB higher than the levels expected from the sensors alone. The additional noise is attributed to the data acquisition equipment. The use of an ACO WS7 windscreen was shown to be extremely effective in mitigating broadband wind noise.