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Left is scalogram of exponential chirp, right is of a bunch of these within time shifts (Shepard Tone):

Is there audio terminology for describing this, besides "rising frequency"? Rising pitch? Rising timbre? Would the two cases be described with different phrases (ignore cross-fading etc for the right case, just focusing on the rising aspect)?

The idea's to describe any positive slope in time-frequency - I have a method that does it, and would like an audio-friendly wording to label it. It should also go the other way, for "falling frequency".

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  • $\begingroup$ Maybe a sweep ? $\endgroup$
    – audionuma
    Dec 28, 2022 at 12:49
  • $\begingroup$ @audionuma I seek to replace "frequency", "rising" / "falling" should stay. "Rising sweep"... doesn't quite work for me. $\endgroup$ Dec 28, 2022 at 12:57
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    $\begingroup$ That "Shepard Tone" is really cool! Wish I could upvote twice. Happy New Year $\endgroup$ Dec 29, 2022 at 14:41

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A few points:

  1. Rising or falling frequency is fine (IMO). For sweeps people often use "up" sweep or "down" sweep.
  2. The slope of a linear sweep can be measured in $Hz/s$ for a log sweep it's better to use "octaves per second".
  3. "Timbre" is definitely wrong here. Timbre is a perceptual quantity that's related to certain frequency areas of high vs low energy but not to the fundamental frequency or pitch.
  4. "Frequency" is a physical quantity. "Pitch" is a perceptual quantity. They are both related but they are definitely not the same. Case in point: The Shephard Tone is an example of where they disagree. The frequency follows a sawtooth wave, but the pitch is continuously rising. The "jump back" of the frequency is not audible. Another one is "missing fundamental". If you have a signal made up of 200Hz, 300Hz, 400Hz, .. the perceived pitch will be that of a 100Hz sine wave despite the signal not containing any energy at 100Hz at all.
  5. Best practice: if you describing something physical use a physical terminology, if you describing human perception use a perceptual quantity.
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  • $\begingroup$ Right, I wondered if I was missing some basic terminology, guess not. Good distinction on physical vs perceptual. $\endgroup$ Dec 28, 2022 at 13:01
  • $\begingroup$ I don't believe your description of the shepherd tone is quite right. The tone obscures where the jump in pitch is, but there still is a jump in pitch, you would not describe the pitch as being in the 10th octave after listening to a few repetitions. $\endgroup$
    – Edward
    Dec 29, 2022 at 0:33

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