Kinsler,L.E. & Frey,A.R.,1962, Fundamentals of Acoustics, 2nd Ed. states " In a broad sense, acoustics may be defined as the generation, transmission and reception of energy in the form of vibrational waves in matter...Many different types of vibration occur in the generation and propagation of acoustic waves.In a narrow sense, their frequency is limited to the range from about 20 cycles per second to 15,000 cycles per second, which produce the auditory sensation of sound for the average person... In a broader sense they also include both ultrasonic frequencies above 15,000 cps and inaudible infrasonic frequencies below 20 cps."