In general, a sound refers to a vibration that is picked up by the human ear. As a sound is generated, it is blasted in waves that vibrate in a frequency measured in hertz (Hz). In the picture below is two sound waves, the lower tone (longer wave) on the left and the higher tone (shorter wave) on the right. For example, a very low deep base sound could be 30 Hz and a high or an upper treble sound could be 2.6 kHz. The average human can hear between 15 Hz to 20 kHz.