Several years ago I made a video for the Sunday School at my church. Background noise was a problem so I bought a relatively cheap shotgun mic with a rubber suspension mount and it made a huge difference. Allen -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Neil Sent: Monday, January 21, 2019 5:34 PM To: Microcontroller discussion list - Public. Subject: Re: [EE] Microphone speech bandpass filter 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 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, specifically from the kid (robot-side) to the remote operator. I ran some tests with a cardioid condenser handheld mic/transmitter (Shure > SM58 FWIW) and it picks up voice well, but I'd like it to get less surrounding 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 88 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 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/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 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 divider 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/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist > --=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 --=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 .