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Re: changing a sound signal while listening to it

You need continuous real-time synthesis for this.  My 
Daqarta program can do this easily, and output to a 
standard Windows sound card.  

Daqarta is not a language like Matlab, it is a stand-alone 
application. It has controls hard-wired to control various 
features of the signal.  You can directly set any control 
(like frequency or level), or you can write macros that 
automate any set of tasks (like increasing one frequency 
and decreasing another by a fixed step size, so the center 
remains the same).  The macro approach may be better if 
your subjects are going to be changing things themselves, 
since you can give macros descriptive names that they can 
choose from a list, and/or you can assign relevant hot-keys 
for convenience.  The subject doesn't need to see the 100s 
of other controls for modulation, waveshape, etc.

Daqarta also shows you the spectrum, waveform, or 
spectrogram of the generated sound in real time, so you can 
see the effects of the changes as well as hear them.

You can download and try Daqarta for 30 days/30 sessions.  
After that, you can't store new macros, or analyze signals 
from the sound card input channels (though you can still 
analyze the outgoing signals), but everything else 
continues to work forever... you might not need to buy it 
at all!

As it happens, I will be off-line for a week or two 
starting tomorrow.  If you have any questions, I'll be glad 
to help today or afterward.

Best regards,

Bob Masta

On 10 Aug 2010 at 10:32, Daniel Bowling wrote:

> Dear List,
> I am trying to create a piece of software that will allow a subject to
> change the beat frequency and amplitude of a signal while listening to it in
> real time.
> More specifically, the signal will consist of two pure tones (e.g. T1 + T2),
> and the difference between them (T2 - T1) as well as the root mean square
> amplitude will be under the control of the subject via the keyboard.
> I have tried to execute this in Matlab using a loop, the problem is that the
> sound stops and then starts again at the beginning of each loop iteration.
> Can anyone suggest a way this might be implemented on a computer? Or perhaps
> just a suitable programming language?
> Thanks,
> Dan Bowling

Bob Masta
            D A Q A R T A
Data AcQuisition And Real-Time Analysis
Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!