I tried the Voice Bandwidth Filter circuit and the results are astounding but not without some effort and one open question. I imagine you won’t be able to comment too much without trying the circuit and seeing its impact on the input to MOVI, but I’ll wrap up with it in any case for your consideration.
The longer story - I tried the Voice Bandwidth Filter without any changes to my code and MOVI became less responsive initially with anything other than a quiet room (car). I put the microphone debug on and found that it was not hearing any engine rumbling, but it would tend to cut off my callsign about half way through. So I started dropping the tolerance. Once I got all the way down to 3, MOVI started to hear my complete callsigns and commands, but continued to “ignore” the engine rumbling at idle. I was encouraged so I moved on to the next trial using 3 as a fixed tolerance.
I was amazed to find that with the Voice Bandwidth Filter circuit in play and a tolerance of 3, MOVI would hear my callsign and commands quickly and accurately while driving up to about 50MPH. I even rolled the windows down at one point and still, MOVI was disinterested in the background noise, hearing and responding only to my voice (I wore only one earbud to listen to the microphone debug which in my understanding is legal!) After 50MPH, things got less reliable and I’ll need an assistant to really listen to the microphone debug to see if it generates any ideas, but I wouldn’t be surprised if it’s just too much convoluted noise to do anything about. Regardless, I’m very impressed with the results I have achieved and would consider it a success!
The open question I have is - would it make any sense to allow us to drop the tolerance below 2 (ie. 1,0) for those of us who wish to filter the signal externally with a filter such as this Voice Bandwidth Filter?
I should probably reiterate the pieces I have in my microphone circuit here because it’s quite a chain at this point:
ADAFruit 9814 Mic -> Voice Bandwidth Filter -> Line-to-Mic level attenuator -> Ground Loop Isolator -> MOVI
[Last edited May 25, 2016 17:48:52]