A miniaturized acoustic vector sensor with PIN-PMN-PT single crystal cantilever beam accelerometers

Directional sound detection using vector sensors rather than large hydrophone arrays is highly advantageous for target detection in SONAR. However, developing highly sensitive and compact vector sensors for use in a system whose size is limited has been a challenging issue. In this paper, we describe a miniaturized acoustic vector sensor with piezoelectric single crystal accelerometers for the application in towed line arrays. A mass-loaded cantilever beam accelerometer with a [011] poled PIN-PMN-PT single crystal shows a better signal-to-noise ratio compared to accelerometers with other piezoelectric materials because of its superior piezoelectric properties in the 32 direction. We suggested a sufficiently compact vector sensor by using a cylindrical hydrophone with 10 mm in diameter as a housing of the single crystal accelerometers. Two single crystal accelerometers were orthogonally mounted inside the cylindrical hydrophone to detect direction of sound in the transverse plane of the line array. The receiving voltage sensitivity of the accelerometers and hydrophone was −199 and −196 dB, respectively, at 3 kHz. The directional cardioid beams generated by summing the omnidirectional beam from the hydrophone and the dipole beam from the accelerometers were validated over the entire operating frequency.