In a message dated 9/9/02 8:02:09 AM Eastern Daylight Time,
Post by markHi,
For a piece I am working on I want to synthesize a
sound like the sound of wind in the trees - for
various reasons I want to synthesize this rather than
sample it.
My guess as to an approach is to filter white noise but
I am not sure what the best approach is - has anyone
got any experience of making this kind of sound? and
is anyone able to give me any pointers..
cheers
mark
Hi Mark:
Well, your success is tied, somewhat, to the kind of synth your using. Also,
your knowledge of its operation, but most importantly -- your ears.
I'm glad you posted this because this is one area of sound design that I've
spent a lot of time with.
Before I get to the synthesis, I'd like to call your attention to a few
considerations:
Many times a successful sound will depend on whether it will be used as part
of a piece, example, wind in the background of other audio material. The ear
is more forgiving if the sound your trying to emulate has other suggestive
sounds that add to the overall picture, so it will be helpful to know how you
plan on using it.
If you don't have a specific project or piece that you need to place it in
and you just want to establish it as a patch/program, then please note that
you will have to remember, as above, not to be too worried if you are not
completely satisfied. It may be entirely useful within the context of a
composite presentation. Again, even if you are very good at this sort of
thing, your synth may have some weak areas that inhibit the goal.
Are you using a standard sample playback synth - Roland, Korg, etc.? If so,
then the biggest disadvantage here is that the white noise is sample looped
which causes too much attention to the loop and sample transposition
anomalies. After I finish here, it will be helpful if you email me with the
specifics of your set up and also you could upload a .WAV file to me so I can
see how you're progressing, then I could help you on a progressive basis.
Basically here is what you need to do.
1. If all you have is white and pink noise, then start with white. Select a
high pass filter with at least a 24 dB slope whose cutoff is around (at
least) 1,300 kHz.
2. If it's a looped sample (usually short), try to determine its original
frequency, ex. if it was placed at c4 on the keyboard and you keydown a c6,
you will get a noticeable and unusable repetition. The key here, is that if
you don't have a steady state source, the ear is sensitive to the loop.
3. "Variation, Variation." This is the crucial touch for success. Even if
your source isn't very good, a believable result can be obtained with the
proper variation/modulation. Keeping things simple (at first), grab an LFO
and depending on the waveforms available for the LFO, choose "Random," if you
don't have that, then start with a simple triangle type. Again, additional
modulations of the simple LFO can be applied later.
4. Assign the LFO to the Filter and if the LFO waveform parameters allow you
to have a "positive only" function, then choose that, unless the waveform is
already a positive triangle. This is because you don't want to have the
filter cutoff to be going lower than your original cutoff-unless of course
you start the cutoff higher than needed and then use the LFO to bring you
back towards the original. But, in that case you'll have to choose a bipolar
waveform for the LFO so that you can sweep down and up.
5. Choose a mild amount of modulation of the filter from the LFO. It should
affect the filter gently, unless your aim is to produce a violent windstorm
through the trees. Make sure you don't have any resonance applied to the
filter and that no reverb or other effects are inline. The LFO
speed/frequency should be somewhat slow...0.25 to 0.50 Hz. Please remember
that everything that I say is a starting point and that many details must
eventually be applied.
6. If you have another LFO, then grab that and set it to approximately the
same as the other one and assign it to "Pitch" by a small to medium amount
and in this case, the LFO waveform could be bipolar or not, use your ears.
The key to wind thru trees with leaves is different from wind thru leafless
trees, in which case, you will start to apply some resonance to the filter.
7. At this point, realism demands slow and fast and variable randomness to
both the filter, pitch and AMP. These modulations to the LFOs can be had
simply, at first, by choosing the LFOs that you've already set up, to be a
mod source (to those LFOs themselves) which will mod the speed and depth
amounts of the original LFO mod amounts that are applied to the filter/pitch
and at this point - the AMP (remembering to start with small amounts and move
thru larger amounts, or if you have additional LFOs, use them to mod the
original LFOs.
8. Set up a couple of envelopes, one with small amount (level) parameters and
medium time settings and the other with faster time settings and larger level
settings.
Have them modulate, directly AND in addition to the LFOs, the
filter/pitch/amp, then try instead, having them mod the LFOs, either the
original LFOs which are modulating filter/pitch, or the LFOs which were set
to mod the original LFOs. Next, try modulating the envelopes with any of the
LFOs. At this point depending on the synth, you should be able to see what is
possible. The quality of the source wave will determine how you set your
filter. The filter design will determine your cutoffs, etc.
There are many other little things to do which can be difficult to describe
without knowing your synth. I can honestly say that I have had excellent
results within the compromises of my own synths. When you obtain success, you
will be able to make soft breezes, whipping winds and others as well as ocean
waves of various sorts using the same principles except for the filter target.
9. Besides white noise, see if you have any waves that fall into the category
of rustling, scraping, snapping, sizzling, noise, etc. Filter with lowpass to
mask the obvious transients, mix at low volume with what you have already,
apply to a lesser degree, those mods that already exist with the white noise
wave and in addition, apply some "sample and hold" mod in very small amounts
to the AMP. ENV. Use whatever mods that are running to mod the S/H parameters
and vise versa (use S/H to mod the others) keeping in mind the small amounts
of everything is where you want to start. However, to produce that occasional
quick rush or flurry through the trees, very important for realism, you will
need to have an occasional LFO, ENV, (AMP.ENV. as well) move quickly and
shortly (in duration) modulating the filters, Amp and a little more so-the
pitch.
Feel free to email me with your set up details and if you wish, to send some
.WAV files.
Sincerely,
Phil Magnotta
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