Algorithms and performance of small baseline acoustic sensor arrays

Abstract

Aeroacoustic sensing is well motivated due to its passive nature and low bandwidth, and processing with array baselines of one to a few meters is well studied and useful. However, arrays of this size present difficulties in manufacture and deployment. Motivated by the desire to develop smaller, cheaper (perhaps "disposable") sensor packages, we consider performance for arrays with small baselines. The performance of angle estimation operating roughly in the [30, 500] Hz regime is limited by the observed signal-to-noise ratio (SNR) and propagation in the turbulent atmosphere. Scattering results in a reduction of spatial coherence, which places fundamental limits on angle estimation accuracy. Physics-based statistical models for the scattering have enabled prediction of network performance, including detection, angle estimation, time-delay estimation, and geolocation. In the present work, we focus on angle estimation accuracy for the short baseline case. While a large aperture is desirable to improve angle estimation, the propagation produces a rolloff in the spatial coherence that ultimately degrades the performance despite increasing the array aperture. We characterize this tradeoff analytically via Cramér-Rao bounds, as a function of SNR, frequency, range, sensor array geometry, and propagation conditions. The results clearly favor shorter ranges and higher frequencies when employing small array baselines.

Fundamentals of energy-constrained sensor network systems

“…Consider the problem of localizing a source using distributed aeroacoustic sensors [74][75][76][77]. Acoustic sensing is a mature technology and is appealing in many applications.…”

A Survey of Time Delay Estimation Performance Bounds

“…In aeroacoustics (sounds propagating through air), signal coherence degrades with increased spatial separation between the sensors due to random scattering caused by atmospheric turbulence. Physics-based statistical models for the coherence as a function of frequency, range, weather conditions, and sensor separation are reviewed and applied to signal processing performance analyses in [50], [24], [34], [23], [25]. Scattering and coherence losses occur in underwater acoustics, e.g., see [31] for an early analysis of the CRB on TDE with scattering, with more recent work in [5], [19] and elsewhere.…”