Hi all,

Background:  I built a robot that will drive around and chat (remote=20
operator) with kids in a crowd, but I've been agonizing over the audio,=20
specifically from the kid (robot-side) to the remote operator.  I ran=20
some tests with a cardioid condenser handheld mic/transmitter (Shure=20
SM58 FWIW) and it picks up voice well, but I'd like it to get less=20
surrounding noise.  The Shure won't fit eaily inside the robot so=20
currently looking at just using a condenser element and transmitting=20
with a Samson Concert 88 TX/RX.

I'm tinkering with physically directing the noise with pipes/tubes and=20
will try a parabolic reflector, but I'm also wondering about using a=20
bandpass filter just after the mic, to be more selective for human=20
voice.  POTS is around 3k bandwidth (300Hz - 3300Hz), which is great for=20
voice/speech/talking.  Would this be an ideal range for limiting speech=20
frequencies here also?

For the actual filter, I was thinking about just going passive so I=20
don't have to worry about split power supplies, but IIRC for something=20
low-power like this, I should be able to create a virtual ground with a=20
voltage divider and an op-amp follower.  Shouldn't active be better for=20
this?  FWIW, I have 12V available on the robot.
Any other thoughts?  Time is of the essence here, so simpler is good,=20
but it has to work well.

Cheers,
-Neil


--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.