The measurement of sound and light is important as it relates to the sense of
hearing and sight, as well as many industrial applications such as the use of
sound waves for the detection of flaws in solids and in location and linear distance
measurement. Sound pressure waves can induce mechanical vibration and
hence failure. Excessive sound levels produce noise pollution. Light and its
measurement is used in many industrial applications for high-accuracy linear
measurements, location of overheating (infrared), object location and position
measurements, photo processing, scanning, readers (bar codes), and so forth