Speech: The range of frequencies important for speech understanding is approximately 250-8,000 Hz, with most of the information for word intelligibility falling between 1,000-4,000 Hz. Music: Music's frequency spectrum can range from 50 Hz (a deep bass feeling) to 16,000 Hz (the "overtones" and resonances which contribute to the distinct sound of a cymbal or bell). Hertz (Hz) is the unit of frequency that measures the number of cycles or events per second. It is commonly used to describe sound waves, electromagnetic waves, and the clock speeds of electronic devices Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the reception of such waves and their perception by the brain. Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Sounds = pressure v time