Brand new iPhone SE - voice calls, whether through my Plantronics Voyager Legend (with latest firmware update), or on the phone itself, are extremely loud, crackling and distorted. I've turned the volumes down to their lowest levels on the phone, ringer and on bluetooth itself. But still same issue. I can barely stand to be on calls because they're so loud and hurt my eardrums. Had none of this issue with my iPhone 5C. So am extremely frustrated that my newer technology is having this issue. Any advice or commiseration?
I'd back it up and do a reset of the device. Before you restore from backup set the device up as vanilla and see if it still does it (I'm assuming it will). If so, make an appt at an Apple Store, if you live / work near one. You can setup an appt via the iOS Apple store app or their website. This way when you go in to get your device swapped you can say you already tried the reset... which is something they always recommend. They have a way to test your phone, in-store, for mic / speaker issues. They did it to my iPhone 6 last year. It will see / record the audio issuse and theyw will swap it out.
Apple iOS store app: https://itunes.apple.com/us/app/apple-store/id375380948?mt=8
Website link: Genius Bar - Apple Store - Apple
Let us know the outcome!