I understand that a signal that is white noise is stationary (or more properly that the process generating it is stationary).

What if the white noise is delivered as a single pulse or a series of pulses with silence between them? Is that still stationary, or does the pulsatility suddenly convert this into a non-stationary system?

If it is no longer stationary, is there a term of art conveying the information that the signal within the pulse is stationary (e.g., a pure tone or white noise) rather than a non-stationary natural or musical sound?


1 Answer 1


The pulsed process is not stationary. You can use the term "quasi-stationary" to describe a process that looks stationary in short time scales (e.g. during silence, or in the middle of a pulse).

  • $\begingroup$ What I really want is a term that excludes audio signals generated by a stationary process, whether the signal is subsequently pulsed or continuous, but includes all other kinds of audio signals. I can't quite get away with "signals that are not stationary and not quasi-stationary" -- can you think of a phrase that would meet the need? $\endgroup$ Commented Jun 8, 2019 at 21:25
  • $\begingroup$ I'm not sure I understand: basically you can classify most signals as "stationary", "non-stationary" and "quasi-stationary", where "quasi-stationary" is a fuzzy term that means "the signal is mathematically non-stationary but we'll say it is stationary over the time frames we're interested in". Does that help? $\endgroup$
    – MBaz
    Commented Jun 9, 2019 at 15:45
  • $\begingroup$ Yes, that helps. Thank you $\endgroup$ Commented Jun 10, 2019 at 17:21

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