The term acoustics can mean sound or the science of sound. It is in the latter sense that it is used here. Acoustics thus covers all aspects of sound waves, from low-frequency sound waves to ultrasound waves and beyond to what are simply called acoustic waves. As a means of sensing and actuation, acoustic waves have developed in a number of directions. The most obvious is the use of sound waves in the audible range for the sensing of sound (microphones, hydrophones, dynamic pressure sensors) and for actuation using loudspeakers. Another direction that has contributed greatly to the development of sensors and actuators is the extensive work in sonar - the generation and detection of acoustic energy (including infrasound and ultrasound) in water, initially for military purposes and later for the study of oceans and life in the oceans, and even down to fishing aids. Out of this work has evolved the newer area of ultrasonics, which has found applications in the testing of materials, material processing, ranging, and medicine. The development of surface acoustic wave (SAW) devices has extended the range of ultrasonics well into the gigahertz region and for applications that may not seem directly connected to acoustics, such as oscillators in electronic equipment. SAW devices are important not only in sensing, especially in mass and pressure sensing, but also in a variety of chemical sensors.
Acoustic Sensors and Actuators, Page 1 of 2
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