Normally used in the context of the USB computer data interface. A hub is a device used to expand a single USB port into several, enabling the connection of multiple devices. Particularly useful where multiple software program authorisation dongles must be connected to the computer.

Random noise caused by random electrical fluctuations.

A misnomer, but used to refer to digital formats with long word-lengths and high sample rates, eg. 24/96 or 24/192. Audio resolution is infinite and identical to analogue systems in properly configured digital systems. Word-length defines only the system’s signal-to-noise ratio (equivalent to tape width in analogue systems) , while sample rate defines only the audio bandwidth (equivalent to tape speed in analogue systems).

The upper portion of the audible frequency spectrum, typically denoting frequencies above about 1kHz.

A filter which passes frequencies above its cut-off frequency, but attenuates lower frequencies. Also known as a 'low-cut' filter.

The standard measurement of frequency. 10Hz means ten complete cycles of a repeating waveform per second. (Previously defined as 'cycles per second or CPS).

The available ‘safety margin’ in audio equipment required to accommodate unexpected loud audio transient signals. It is defined as the region between the nominal operating level (0VU) and the clipping point. Typically, a high quality analogue audio mixer or processor will have a nominal operating level of +4dBu and a clipping point of +24dBu - providing 20dB of headroom. Analogue meters, by convention, don’t show the headroom margin at all; but in contrast, digital systems normally do - hence the need to try to restrict signal levels to average around -20dBFS when tracking and mixing with digital systems to maintain a sensible headroom margin. Fully post-produced signals no longer require headroom as the peak signal level is known and controlled. For this reason it has become normal to create CDs with zero headroom.

The part of a tape machine or disk drive that reads and/or writes information magnetically to and from the storage media.

The addition of harmonics that were not present in the original signal caused by non-linearities in an electronic circuit or audio transducer.

High frequency components of a complex waveform, where the harmonic frequency is an integer multiple of the fundamental.