Pat did an iOS 10 update with the iPhone 6S and he's found out the volume has been dramatically cut in half. Leo says that it's a widespread issue and sometimes it takes awhile to pinpoint the issue and push out a fix. It may be intentional, Apple deciding the volume is too loud for earbuds. It's more likely an issue in the software. There's a noise cancellation setting in accessibility. He can go to General > Accessibility then disable Phone Noise Cancellation. Many are commenting that fixes the issue. Others say it doesn't. It's worth a try, though.