Yes, I'm working on the physics side of it... currently tinkering with=20 various-sized tubes (different lengths and diameters). The mic will be=20 suspended in the middle of the pipe near the back end. I've yet to=20 tinker with wind diffusers such as foam at the front end of the pipe,=20 and I would like to experiment with a parabolic reflector but haven't=20 sourced one yet. Noise cancelling would be great, but I know it would take a lot more=20 time than I have currently, and I won't have access to the actual=20 environment available until d-day. I'm using other crowded spaces=20 test, trying to see if I can isolate one person's voice. FWIW, the=20 person speaking to the robot does not need to be perfectly isolated...=20 the operator just needs to hear the person clearly enough to understand=20 them. Asking them to repeat what they said is not an option. Cheers, -Neil. On 1/21/2019 1:59 PM, David Van Horn wrote: > LTSpice would be good for modeling the filter. > The filter is a good idea, but making the pickup more directional would b= e 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 erro= rs 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, s= pecifically from the kid (robot-side) to the remote operator. I ran some t= ests with a cardioid condenser handheld mic/transmitter (Shure > SM58 FWIW) and it picks up voice well, but I'd like it to get less surrou= nding noise. The Shure won't fit eaily inside the robot so currently looki= ng at just using a condenser element and transmitting with a Samson Concert= 88 TX/RX. > > I'm tinkering with physically directing the noise with pipes/tubes and wi= ll try a parabolic reflector, but I'm also wondering about using a bandpass= filter just after the mic, to be more selective for human voice. POTS is = around 3k bandwidth (300Hz - 3300Hz), which is great for voice/speech/talki= ng. 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= have to worry about split power supplies, but IIRC for something low-power= like this, I should be able to create a virtual ground with a voltage divi= der and an op-amp follower. Shouldn't active be better for this? FWIW, I = have 12V available on the robot. > Any other thoughts? Time is of the essence here, so simpler is good, but= it has to work well. > > Cheers, > -Neil > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/cha= nge your membership options at http://mailman.mit.edu/mailman/listinfo/picl= ist > --=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 .