Piezoelectric materials have been used for decades in hydroacoustic sensors, mostly as cut bulk sensors or in cylindrical or spherical form made of PZT . Water flow around the sensors causes turbulences in the boundary layer and leads to hydrodynamic pressure variations. Using single sensors these pressure variations cannot be distinguished from acoustic signals and are therefore a noise source of major concern in measurements , especially in the low frequency range which is of interest in the field of underwater noise monitoring.
In this work, piezoelectric thin films sensors are used for measurements of the turbulent boundary layer as well as acoustic signals. Separation of these components is achieved by a time-dependent data analysis of simultaneous recorded signals from multiple sensors, which have a flush-mounted design to minimize the influence on the turbulent boundary layer. The sensor array provides an improved spatial resolution compared to arrangements of traditional flush mounted hydrophones due to the size of the individual sensor elements. In spite of the sensor size a good sensitivity can be reached. To study the performance of the sensors, measurements of the turbulent boundary layer and acoustics have been conducted with an acoustic transducer under laboratory conditions and in salt water with free-field conditions.
Financial support from German Navy grant E/E71Z/E0340/AF169 and E/E71Z/G1651/AF169 is gratefully acknowledged
 C. H. Sherman, J. L. Butler, Transducers and Arrays for Underwater Sound, Spring Sciences + Business Media New York 2007.
 C. N. Dolder, M.R. Haberman, C.E. Tinney, A laboratory scale piezoelectric array for underwater measurements of the fluctuating wall pressure beneath turbulent boundary layers,
Measurement Science and Technology, Volume 23, Number 4, 2012.