This is a measure of the rate of repetition of a periodic disturbance – e.g. a sound wave. It is measured in hertz (Hz) and is physically the number of cycles per second.</p>
<p>In terms of audible sound, low frequency is subjectively the bass; high frequency is treble and upwards.</p>
<p>Humans are typically capable of detecting sounds over a frequency range of 20 to 20 kHz (kilohertz), with greater sensitivity between 1 and 5 kHz. Sounds below 20 Hz are termed infrasound, whilst sounds above 20 kHz are termed ultrasound.