Appendix B. Glossary

Audio context

A container for all audio nodes in the Web Audio API graph.

Bit depth

The number of bits allocated for each value in an audio data stream.

Bit rate

The number of bits per second that a compressed audio file will output.

Cents

A logarithmic unit of measure used for musical intervals. Twelve-tone equal temperament divides the octave into 12 semitones of 100 cents each.

Clipping

What happens to an audio wave when it exceeds the highest permitted value (0 dBFS).

Decibels

A relative unit used to measure the intensity of a sound signal.

dBFS

Sound level relative to the full scale (nominally 0 dBFS). This unit is negative unless sound is being clipped.

dBSPL

Sound pressure level relative to the threshold of human hearing.

FFT

Fast Fourier Transform, an algorithm for breaking a sound wave up into its constituent sine waves.

Hertz

A measure of frequency. The number of times per second that something happens.

Nyquist frequency

Half of the sample rate of an audio buffer.

PCM

Pulse code modulation, a way of storing sound waves as an array of numbers.

Playback rate

The speed at which an audio buffer is played back.

Sample rate

The number of times per second that an analog sound is sampled during quantization, or the process of converting an analog signal into a digital one.