What is Bandwidth?

A bandwidth is simply just a range of frequencies. This can be 10Hz to 100KHz, 1KHz to 5KHz, 1MHz to 5MHz...any range of frequencies.

Usually in audio testing, the bandwidth that is used is 20Hz-20KHz. This is because this is the farthest range from bass to treble that a human being can hear. The human beings with the sharpest hearing may be able to hear as low as 20Hz and as high as 20KHz, but after those lows and highs, a human being cannot hear any other sounds outside of this bandwidth.

So when microphones and speakers are tested in audio labs, this bandwidth, again of 20Hz-20KHz, is used to test their sound outputs. Microphones must be able to record low basses and high trebles, while speakers must be able to output low basses and high trebles.

Below is an example of a microphone tested for its frequency response with the bandwith of 20Hz-20KHz:

When testing with this bandwidth, it can be seen how each microphone responds to each frequency within this bandwidth.