I have a robot that connects to a smart phone via the phone's headset jack for bi-directional communications. The robot has a mic that I can use that will send audio received from its mic to the phone. It works fine except there is a loud low hum coming over the line. The hum does not change at all by varying my location in my home so it looks like it's the bot, or some impedance match or something between the bot and the phone. Is there a way to tell the Lumia phone from C# to get audio input from it's microphone instead of from the headset jack? That would solve the problem for me.