DUDU-Meng The active microphone I mentioned requires a 12V power supply. I previously encountered an issue where modifying the car's built-in microphone and connecting it to the DUDU7 caused a humming noise. Its microphone module requires a 12V power supply.
I've connected the OEM VW microphone and it works very well. Needed a separate phantom power feed as well though. While the VW microphone needs 5V, the Dudu7 only provides something between 2.5-3V. I have very clean call quality. The Dudu7 noise cancelling also works well. People can hear I'm hands free but cannot hear I'm in a car. Call quality doesn't suffer from road surface, speed, etc, it's all neutralised. So OEM microphones can work very well but need adaptation and in your case I think someone supplied dirty power.
@TattooHH try to put the microphone onto the cover of the steering column in front of the instrument cluster, that's often the best position. Decouple the mic housing from car vibration (foam pad sticker). Voice will be much louder. If the other side hears echo, the gain is too high (mic picks up speakers and loops back to caller). If placed better, gain can be reduced.
@Mikescotland Dudu7 has noise cancelling in it's microphone circuit, I don't know other Android units that have it. It works by filtering more or less steady sounds (e.g. engine, wind, tire noise). Can be tested by making an even noise/hum eg with your voice, it will be dampened after a second or so. Maybe that's what they mean, I guess the filtering is digital. The microphone itself is very analogue 😉
