I could not find a clear answer to that and it's driving me nuts, because I have a microphone, which when connected to my phone via 3.5mm jack picks up a sort of buzz, as if from wireless inteference. Expectedly, the buzzing stops when I put the phone in airplane mode. Also, the mic doesn't pick up anything from other phones or WiFi routers transmitting.
Curiously enough this buzz is not present when the mic is connected to other phones or a computer.
I have also tried different recording apps... without any improvement.
I figured this could be due to some potentially faulty connection between the phone's audio interface(?) and the transceiver, but am not sure if there is a connection between the two.