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Exlextronix
05-23-2005, 05:08 AM
Hi, I am new to this forum, but just recently I obtained the basic stamp 2 developing kit. I was wondering if it would be possible to use it to take incoming sound waves and invert them, then send them out a speaker, effectively canceling out the sound. if it is possible how would I go about creating this?

shandar
05-23-2005, 07:43 PM
I was thinking about that a few months ago, but I think that the basic stamp is way too slow to do that. Either you have to use a PIC or somehow create some kind of electrical circuit that does it. Not sure though, but if you find a way to do it give me a shout!

allanlane5
05-23-2005, 08:28 PM
Yes, the BS2 is way too slow to do something like this. What you need to do is recieve the sound through a microphone, invert the phase of the signal, and output that inverted phase signal. All in real-time.

This is something it takes a circuit to do, not a microprocessor. Also, a few companies (Bose for instance) have invested lots of dollars in the technology to do this. It's not a trivial thing to do.

Paul Baker
05-23-2005, 10:45 PM
All of the above is true, there is no way this could be accomplished with a stamp, the stamp is not powerful enough to playback CD quality wave sounds, let alone perform any complex computations on the data. A DSP designed for real time stream manipulation could do it, or complex dedicated circuits like in the Bose system (which btw is phenomenal quality, Dr. Amar Bose gave a lecture here a couple years back and brought one for us to try out). It not only requires negative phase transform but equal amplitude to offset unwanted audio signals. If I remeber correctly he designed a chip which performs the inversion using HRTF transforms (Head Related Transfer Function).

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Exlextronix
05-24-2005, 02:57 AM
Ah, oh well. It was worth a try.

Thanks for your input!

mm
05-24-2005, 08:05 AM
http://www.headwize.com/projects/noise_prj.htm

Check the web page above for a simple analog solution to what you want to do, this design is popular with ham radio ops and with private pilots. This circuit does work very well.


Mike