Development of an accelerometer-based underwater acoustic intensity sensor

Abstract

An underwater acoustic intensity sensor is described. This sensor derives acoustic intensity from simultaneous, co-located measurement of the acoustic pressure and one component of the acoustic particle acceleration vector. The sensor consists of a pressure transducer in the form of a hollow piezoceramic cylinder and a pair of miniature accelerometers mounted inside the cylinder. Since this sensor derives acoustic intensity from measurement of acoustic pressure and acoustic particle acceleration, it is called a p-a intensity probe. The sensor is ballasted to be nearly neutrally buoyant. It is desirable for the accelerometers to measure only the rigid body motion of the assembled probe and for the effective centers of the pressure sensor and accelerometer to be coincident. This is achieved by symmetric disposition of a pair of accelerometers inside the ceramic cylinder. The response of the intensity probe is determined by comparison with a reference hydrophone in a predominantly reactive acoustic field.

Particle motion measured at an operational wind turbine in relation to hearing sensitivity in fish

“…Knudsen et al (1992) and Lu et al (1996) used accelerometers mounted on vibrating tanks or tubes. McConnell and Jensen (2006) presented results for a pressure-acceleration probe and the development and test of an intensity probe were described by Kim et al (2004Kim et al ( , 2008. However, none of these devices have been used in an offshore environment.…”

Extracting the Green’s function from measurements of the energy flux

“…Measurement of the acoustic energy flux 21 can be carried out by using two nearby microphones, [22][23][24] or using devices that contain a microphone and an accelerometer. 25,26 The proposed method for Green's function extraction can be applied to such measurements. The theory holds for an arbitrary real density q(r) and compressibility j(r).…”

Design and implementation of a shielded underwater vector sensor for laboratory environments

“…[1][2][3][4][5] There are two main components to a p-a underwater vector sensor: a pressure sensor and a particle velocity sensor. A p-a probe with high acceleration sensitivity should be nearly neutrally buoyant in water.…”

“…Therefore the volume of the probe must be chosen so that the mean density of the probe, q p , is nearly equal to the density of water, q o , (998 kg=m 3 ). Second, the size of the probes should be much less than the smallest wavelength of interest.…”