active

[badgers]

anyone try an active noise reduction circuit to quiet down their fans?

At first it looks like 4 bucks in op amps, resistors, caps, and a speaker

I have an old mic and speaker that I have no other use for, so I thought it might be possible.

Any ideas on how to prevent feed back from the speaker to the mic?

thank you for your time and have a good day

[DKYoda]

Thats very interesting ...
Can you cancel out white noise though ??? Hmmmm...

[John Jr]

Will let you know

[badgers]

I don't believe that it is true White Noise.

I am trying to find out if there is a program that will let me use my sound card to capture audio, and then give me a spectral analysis.

I think that there will be one predominate frequency, I can then build a bandpass filter, and an inverting amp to cancel the noise.

I am concerned with time delay of the system causing instability and I hate the S plane.

LHP poles and zeros is really hard for me

[DKYoda]

Delay should be nearly null shouldnt it ???
Mighty close area to deal with ..

[CrystalMethod]

Originally posted by DKYoda
Delay should be nearly null shouldnt it ???
Mighty close area to deal with ..

There's always a bit of delay when you use a mic. I wonder if you could use and inductive pickup as a noise generator, and then fine tune the signal.

[badgers]

if I find a strong dominance of a specific freq then I just may generate that freq and use the mic as an error amp.
Use the op amp to drive the error to zero. That would make it much more stable, but I don't know.

any programs to do spectral analysis and wave form capture(share or free ware?)