Glossary definition of 'Latency'

The time it takes for an audio signal to pass through a system, usually expressed in milliseconds (ms).

Latency is primarily a feature of digital audio systems where the incoming audio signal is processed as digital data. This can include the conversion from analogue voltages to digital data in an AD converter and/or back again in a DA converter, each process of which takes a finite amount of time. Much is made of latency in recording systems as it has the potential to add phase shifts which can in turn add comb filtering to an audio signal. Latency is only a problem where there is a different latency between more than one path of sound. For monitoring, the two paths could be a direct acoustic path and a foldback path.

When it comes to musical performances, latency is seen as undesirable as it can affect the musicians ability to play in time. To put this into context, it should be remembered that sound travels at approximately 340m/s, so standing 2m from a speaker introduces 6ms "latency". As a rule of thumb, 1ms is the time it takes for sound to travel 1ft, 3ms is the time it takes for sound to travel 1m. When monitoring over speakers, you could knock 1ms off the latency by leaning forward...