Sounds like a 56k modem
I just received my Tmobile Note 3 today and I can hear a strange sound coming from the earpiece. I just noticed it now when I tried to make a call.
It sounds like a screeching 56K modem - do you remember that sound whenthe modem starts to dial, sometimes the sound is like when there is an interference when you are near a PA system...
It is louder at the beginning of a re-start just before the main screen comes.
I have listened to my S3 and S4 in the same location, and they are silent.
I have restarted a few times, disabled wifi and mobile internet, removed sim card, factory reset from recovery to no avail. Changed location to another room. The sound coming from the earpiece is still there.
Can you please try listening to your phone if you can hear anything...
Thanks a lot
Galaxy Tab Pro 8.4
Note 3 Stock ROOTED TW 4.4.2 (XXUEND5) -returned for faulty screen N900T - returned for faulty screen and buzzing speaker.
Note 2 - Sold
S4 - FNB8 Stock rooted
S3 - TW 4.3 Stock rooted (Still awesome phone)