BASIC THEORY OF SOUNDSound is a vibration in an elastic medium such as air, water, buildingmaterials and earth. Sound energy progresses in atmospheric pressureand travel a great distance. Sound is the physical phenomenon thatencourages the sense of hearing. It is generated by vibrated bodies in theform of waves of compression and rarefaction in the air. A full circuit by adisplaced particle is called a cycles. The time required for one completecycle is called period and the number of complete cycles per second is thefrequency of vibration. Wavelength of Sound: It is the distance a sound wave traveling during onecycle of vibration or wavelength is the distance between adjacent regions whereidentical conditions of particle displacement occur.