LTSpice would be good for modeling the filter.=20 The filter is a good idea, but making the pickup more directional would be = a big plus. You might consider a noise canceling mic summed in with the other one. It would take some experimentation to get right, phase and amplitude errors= determine how well it will work. -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of Neil Sent: Monday, January 21, 2019 11:09 AM To: Microcontroller discussion list - Public. Subject: [EE] Microphone speech bandpass filter Hi all, Background: I built a robot that will drive around and chat (remote operator) with kids in a crowd, but I've been agonizing over the audio, spe= cifically from the kid (robot-side) to the remote operator. I ran some tes= ts with a cardioid condenser handheld mic/transmitter (Shure SM58 FWIW) and it picks up voice well, but I'd like it to get less surround= ing noise. The Shure won't fit eaily inside the robot so currently looking= at just using a condenser element and transmitting with a Samson Concert 8= 8 TX/RX. I'm tinkering with physically directing the noise with pipes/tubes and will= try a parabolic reflector, but I'm also wondering about using a bandpass f= ilter just after the mic, to be more selective for human voice. POTS is ar= ound 3k bandwidth (300Hz - 3300Hz), which is great for voice/speech/talking= .. Would this be an ideal range for limiting speech frequencies here also? For the actual filter, I was thinking about just going passive so I don't h= ave to worry about split power supplies, but IIRC for something low-power l= ike this, I should be able to create a virtual ground with a voltage divide= r and an op-amp follower. Shouldn't active be better for this? FWIW, I ha= ve 12V available on the robot. Any other thoughts? Time is of the essence here, so simpler is good, but i= t has to work well. Cheers, -Neil -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=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 .