Hello. Around 2 months ago I had a pair of Sony WH-H900N headphones purchased for me (as it was for my birthday I do not know the exact date of purchase), to which I have been using them fairly regularly since.
However, a few days ago I powered them on to use them and there was a very loud low-pitched buzzing coming from the right ear cup. I turned them off and gently blew into the front microphone on it (which I presume is for noise cancelling), then powered them on again and they worked fine. For these past few days I have not had any issues, until today. The buzzing is back, and this time it won't go away. It only occurs with noise cancelling enabled, and my previous methods of trying to stop it didn't work. I can only guess but I don't think it was software related, as mine is up-to-date. From what I have observed it appears that it is the front microphone on the right ear cup. I had used them outside, when it began to rain. However it has been a while since then and I didn't have issues using them earlier, so I am not sure. It occurs even without audio playing, and the left ear cup seems to be fine.
I hope that there is a known fix, as I do like them a lot and they cost quite a bit to me.
