Acoustics is an interdisciplinary science which studies all mechanical waves in solids, liquids, and gases including sound, infrasound, ultrasound, and vibrations. An acoustician is a scientist who works in the field of acoustics and someone who works in the field of acoustics technology is called an audio or acoustical engineer. The applications of acoustics may be observed in nearly all aspects of modern society ranging from the noise control and audio industries to marine and civil industries. Since acousticians have extended their studies to frequencieswell above and below the audible range, it has become conventional to let the word "acoustic" to refer to the entire frequency range without limit(i.e., also including the "infrasonic" and "ultrasonic" ranges). Also, there are several major divisions of acoustics which may be grouped into three key domains:
Physical acoustics: General linear and nonlinear acoustics, Structural acoustics, Under-water sound, and Aeroacoustics.
Acoustical engineering:Ultrasonics, Transduction, Acoustic signal processing, Room acoustics, Architectural acoustics, Environmental acoustics, and Acoustic measurements/instrumentation,
Biological acoustics:Bioacoustics, Physiological acoustics, Psychoacoustics, Speech communication, and Musical acoustics.