[sdiy] Question for those with musical ears
rburnett at richieburnett.co.uk
Thu Apr 15 10:48:05 CEST 2021
There are a few different things to consider here...
Limited pitch update rate causes FM sidebands in a synthesised frequency
sweep because the pitch is no longer sweeping smoothly but is instead
jumping in discrete steps. If the update rate is very slow this is
obviously perceived as a glissando, but if the update rate is higher it can
still be perceived as a roughness to the sound due to the modulation
sidebands. It essentially sounds like phase-noise or phase jitter because
each cycle of the output signal doesn't start and end exactly where it
should. The question of what is perceivable and what is not, is complex
because some combinations of oscillator pitch, update rate and step size
might result in phase-noise that is quite well masked by the spectrum of the
wanted components, whereas other combinations might put phase-noise spectral
lines in regions where they aren't well masked perceptually. In general you
can get away with a lower pitch update rate for tones that have a low
fundamental frequency, and I guess this is the result you would intuitively
expect... The more cycles for which the oscillator pitch stays constant
when it should really be on the move, the more it starts to sound "wrong."
Regarding the ability to perceive small pitch changes... In a highly
reverberant environment, if you keep your head very very still, it can be
possible to detect tiny changes in pitch due to changes in the
constructive/destructive interference at the listening position. But if you
were to move either the source or the listening position even slightly in
between listening to the two tones this ability is quickly lost. As someone
else already pointed out this is really due to the complex frequency
response of the listening environment converting a small frequency change
into a more noticeable amplitude change. Although a given person might
easily perceive that the tone has "changed" they might be hard pressed to
say whether it went up or down in pitch!
Just a few thoughts.
From: Mike Bryant
Sent: Thursday, April 15, 2021 12:47 AM
To: synth-diy at synth-diy.org
Subject: [sdiy] Question for those with musical ears
Consider a continuous glissando played on an analogue synth - the frequency
rises smoothly between the start and end pitches.
But on a digital synth there will always be discrete steps between
successive frequencies as the frequency is gradually stepped between the
start and end pitches.
Question is, what is the minimum step (in cents) needed such that the best
musical ears cannot tell the frequency isn't rising smoothly as on the
analogue synth, but in many discrete steps.
It may be that the rate of change can effect it so if so please assume a
glissando starting at middle C rising at 1 second per semitone.
Synth-diy mailing list
Synth-diy at synth-diy.org
Selling or trading? Use marketplace at synth-diy.org
This email has been checked for viruses by AVG.
More information about the Synth-diy