I've ruled out a number of my factors contributing to the problems I see. For the record, I am iPhone 5, AT&T, St Paul area and I use a wired headset (Apple and 3rd party). My problem is audio clipping on my incoming audio.
I really don't think my problem is a hardware issue, though in modern complex devices there is a thin boundary between software and hardware issues.
There is really only one circumstance I run into SERIOUS problems, though there are subtle issues elsewhere:
a conference call on our corporate Global Conference system when I'm at HOME.
Here are the things that don't seem to matter:
- LTE on or off
- WiFi on or off
- Case on or off
- Position of phone
- Covering or uncovering the rear background-noise-canceling headphone
- Resetting my network settings
- Restarting phone
- Background noise or note
Here is what works
unplug my headset when I've enabled 'hearing aid mode' and llisten to the phone directly or use speaker phone.
I think there are multiple issues in this thread, but, as noted by a few contributors, this looks like an issue with the new-with-iPhone 5 noise cancellation software/hardware Apple is using. The fix is 'hearing aid mode', which probably changes or disables noise cancellation. It is possible that a hardware problem on some iPhones is causing the noise cancellation product to misbehave, but since this is new software, and since for me the problem is so much worse with this one audio source and possibly even with selected cell towers, I'm somewhat optimisitic it will be fixed with next iOS update.
I'm pretty sure Apple's engineers know what's wrong.