Hot topics in engineering acoustics.

Abstract

The maturation of single crystal piezoelectric materials in the past decade has spawned a renewed interest in traditional and new transducer designs for underwater acoustic and medical imaging applications. The engineering of acoustic devices based on piezoelectric crystals began in the first half of the 20th century and was overtaken by developments in ferroelectric ceramic compounds such as barium-titanate and lead-zirconium-titanate (PZT). These materials are now being challenged by engineered relaxor piezoelectric single crystals materials such as lead-magnesium (or zirconium or indium)-niobate-lead-titanate (PMN-PT, PZN-PT, and PIN-PT) in many applications. The new materials have tremendous improvements in piezoelectric properties including electromechanical coupling coefficients exceeding 90%, which can double the power factor bandwidth for underwater projectors, sound speeds that are a factor of 3 lower than PZT that enable compact low frequency sources, and strain levels as high as 1% for high drive and actuator applications. The hot topics related to engineering acoustics involve the development and commercialization of devices based on new and traditional transducer designs that exploit the novel properties of the new crystal materials. Examples of broadband underwater communications transducers, tonpiltz sonar projectors, pressure and pressure-gradient hydrophones, mechanical actuators, and medical devices are presented.