Pseudorandom noise is a signal similar to noise which satisfies one or more of the standard tests for statistical randomness.

Although it seems to lack any definite pattern, pseudorandom noise consists of a deterministic sequence of pulses that will repeat itself after its period.

This sequence is known as a chip and the inverse of its period as chip rate.

In cryptographic devices , pseudo-random noise is mixed with entropy to increase randomness.

Pseudorandom noise is used in some electronic musical instruments, either by itself or as an input to subtractive synthesis.

In spread-spectrum systems, modulated carrier transmissions appear as noise to any receiver that is:

1. not locked on the transmitter frequencies; or
2. incapable of correlating a locally generated pseudorandom sequence with the received signal.

A pseudonoise code is one that has a spectrum similar to a random sequence of bits but is deterministically generated.

See also: Pseudorandom number sequence, Pseudorandom number generator, n-sequence, Federal Standard 1037C, MIL-STD-188