ABSTRACT
This chapter discusses important aspects of hearing sensitivity and frequency range, presents an introduction to the decibel in its various applications, and considers the speed of sound and the concept of wavelength. Sound is the human perception of vibrations in the region between 20 Hz and 20 kHz. Sound is a wave motion in the air, and all wave motions, whether on the sea, vibrations through the earth, radio waves, light waves, or whatever else, follow many of the same universal physical laws. The decibel is, these days, one of the most widely popularised technical terms. Strictly speaking, it expresses a power ratio, but it has many other applications. Hearing perception is a world where everything seems to be on an individually sliding scale. Psychoacoustics is the branch of the science which deals with the human perception of sound, and it has made great leaps forward since the 1980s.
