The third article on multi-phone processing addresses beamforming, which is a technique that is different to multi-phone localization or multi-phone direction finding. Both methods (localization and direction finding) require first the detection of signals and then allow the signal processing. Beamforming can be considered as spatial filters that maximizes the response (beamformer output) for any…
The second article in the Multi-phone Processing series explores the technique of direction finding for sound sources. Direction finding becomes the preferred approach when localization is impractical, such as when the sound source is located at a significant distance from the hydrophone array. In this context, “significant distance” typically refers to a distance that is…
This is the initial article on multi-phone processing, focusing on utilizing multiple hydrophones to acoustically localize active sound sources. The primary goal of multi-phone processing is to determine the 3D coordinates of a sound source. Future articles will explore techniques for identifying only the directions to sound sources, followed by a detailed discussion on beamforming.…
The Goertzel algorithm efficiently computes the discrete Fourier transform (DFT) for a limited set of frequencies. Unlike the traditional DFT, which involves multiplying each sample by a complex number and summing the results, the Goertzel algorithm utilizes real-valued coefficients (the cosine of the target frequency) and includes one additional addition operation. The complex spectrum is…
Theoretical considerations are presented here to estimate the sensitivity of piezo ceramic hydrophones, focusing on cylindrical and spherical designs. The provided equations predict the voltage generated as a function of external sound pressure, serving as an estimate for expected free-field sensitivities. However, realistic effective sensitivities, which account for the influence of attached electronics and nearby…
Ambient noise consists of various components, which are detailed in the following discussion. Four primary noise sources are examined more closely. Specifically, ship noise, as represented by the Wenz curves, and wind-driven surface noise are presented both as digitized data points and through mathematical equations. To provide a comprehensive overview of the basic noise spectrum,…