Abstract
In this work, we design a small-sized bi-cone acoustic vector-sensor array (BCAVSA) and propose a frequency invariant beamforming method for the BCAVSA, inspired by the Ormia ochracea’s coupling ears and harmonic nesting. First, we design a BCAVSA using several sets of cylindrical acoustic vector-sensor arrays (AVSAs), which are used as a guide to construct the constant beamwidth beamformer. Due to the mechanical coupling system of the Ormia ochracea’s two ears, the phase and amplitude differences of acoustic signals at the bilateral tympanal membranes are magnified. To obtain a virtual BCAVSA with larger interelement distances, we then extend the coupling magnified system into the BCAVSA by deriving the expression of the coupling magnified matrix for the BCAVSA and providing the selecting method of coupled parameters for fitting the underwater signal frequency. Finally, the frequency invariant beamforming method is developed to acquire the constant beamwidth pattern in the three-dimensional plane by deriving several sets of the frequency weighted coefficients for the different cylindrical AVSAs. Simulation results show that this method achieves a narrower mainlobe width compared to the original BCAVSA. This method has lower sidelobes and a narrower mainlobe width compared to the coupling magnified bi-cone pressure sensor array.
Highlights
Interest in the measurement of the radiated noise has increased considerably in the last two decades, driven by a recognition of safeguarding the national marine safety
We provide some computational simulations to illustrate the frequency invariant property of the proposed method and the advantages of the proposed method compared to the original bi-cone acoustic vector-sensor array (BCAVSA) and the bi-cone pressure sensor array with the same configuration parameters
Each cylindrical acoustic vector-sensor arrays (AVSAs) consists of two UCAVSAs, and each UCAVSA is composed of eight Acoustic vector sensors (AVSs)
Summary
Interest in the measurement of the radiated noise has increased considerably in the last two decades, driven by a recognition of safeguarding the national marine safety. In order to obtain a higher gain, an array composed of many pressure sensors is usually used in the sonar system, which leads to a high cost. As the AVS can make use of the extra available acoustic particle velocity information, the arrays composed of AVSs have some attractive advantages compared to the pressure sensor arrays with the same configuration, such as higher spatial gain [10], stronger ability to suppress noise [11], lower direction-of-arrival (DOA) estimation error [3,12], etc. The size of the bi-cone sensor array is always restricted to some practical application platform such as the shallow sea. This paper aims to propose a method for a small-sized bi-cone sensor array to form the constant beamwidth pattern to measure the low-frequency radiated noise
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