Re: Simulating Vibrato With Sine Wave
Re: Simulating Vibrato With Sine Wave
- Subject: Re: Simulating Vibrato With Sine Wave
- From: Richard Dobson <email@hidden>
- Date: Mon, 01 Feb 2010 16:20:22 +0000
On 01/02/2010 15:55, Hank Heijink (Mailinglists) wrote:
On Feb 1, 2010, at 10:24 AM, Richard Dobson wrote:
For vibrato (pitch variation) a plain sine-modulated (and
interpolating) variable delay line will do it very nicely. For
tremolo (amplitude variation) you simply have to set your median
level and mod level, and multiply signal with your slow sine.
Median level +- sine amplitude must be all positive, and< 1.0.
E.g. set sine to range between 0.25 and 0.75, to get a 6dB
variation : vibsig = 0.25 + (0.5 * sin(w)); out = in * vibsig. To
sound like real human vibrato, the frequency of the sine and/or
amplitude should be a little randomised; which is where things get
"interesting".
Randomisation won't do it. Things get interesting indeed - vibrato is
the topic of shelves of research theses, and depending on the
instrument (voice included) can be very tightly controlled and
modulated. I have yet to hear a convincing synthesized vibrato, which
is why I suggested tremolo. Not the same, but a lot easier to
synthesize convincingly.
Well, it will get you quite a way. Sundberg IIRC considers both slow
drift and faster "jitter" as measured aspects of vocal vibrato, both of
which can be reasonably modelleld by summed random variations of the
primary modulation source (probably need 1/f noise rather than white). I
think it is fair to regard these as aspects of most instrumental vibrato
too. All sorts of further complications arise in modelling note
transitions. Overall the principle is that if you immediately notice it,
it is too much. But if it is not there, on the other hand, you pretty
well immediately know it is synthesised or in some sense artificial. All
much easier to manage of course when it is integrated into the synthesis
engine itself. Adding it externally inevitably brings compromises, most
obviously in respect of timbre, formants, etc. Vocal vibrato (as violin
etc) is almost entirely pitch variation, so for that tremolo will not
get you there at all.
Richard Dobson
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