What is sound
Sound is changes in the air pressure, oscillating around the atmospheric pressure. For the human ear, the important parameters are the frequency and the sound level. The frequency is measured in Hertz (Hz), and describes how many times per second the sound pressure oscillates around the atmospheric pressure. At low frequencies the sound is low (bass) and at high frequencies the sound is high (treble). The sound level is measured in decibel (dB) on a logarithmic scale, and describes the deviation in air pressure from that of the ambient atmospheric pressure. Typical conversation is measured to be 60 dB, an increase to 70 dB will be perceived as a doubling of the sound intensity.
Sound is pressure waves travelling through air. Sound absorption is the absorption of sound waves in a material and is
the process where sound energy is dissipated into heat energy. The sound absorption properties of a material are characterised by the sound absorption coefficient α, and vary from 0 to 1. Sound absorption of a material is frequency dependent.
α = 1.0 equals 100% sound absorption
α = 0.0 equals 0% sound absorption