Re: morphing sounds was LOOPING a DRY CLEANING SHOP

[Rainer Straschill <moinsound@googlemail.com>]

Am 02.10.2011 22:33, schrieb andy butler:
> With that definition of linear I don't think it's possible to change 
> any sound into any other. ...can't create frequencies not present in 
> the source signal.
I can't create other frequencies if the system is linear and time 
invariant (LTI), that is correct, and then all of the system's 
properties are contained in its impulse response or in its fourier 
transform, the (complex) frequency response.

However, if the condition of time-invariance does not hold (which is for 
a time-dependant input signal x(t) and an arbitrary time constant T, is 
f(x(t))=f(x(t+T)) for any T), you can create frequencies not present in 
the source signal - as a simple press on the speed button of your EDP 
(or any use of a modulated but otherwise linear delay, like a 
high-quality chorus/flanger) clearly shows.

           Rainer

note to self: get on and write that blog article about LTI and L and TI 
systems in audio processing now...

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