There are some workarounds, but there’s no real solution for this one.Workarounds: A lot of i Phone 7 owners have been complaining about a mysterious hissing sound coming from the back of the device.
WAIT: Check the Bluetooth Device Batteries and Power Source Before going through the troubleshooting steps below, check the power source of the Bluetooth device, speakers, or stereo. The Bluetooth connection and signal strength will diminish greatly with a weak power source or low battery, and may result in erratic behavior with dropping or failed connectivity.
Swipe up to access Control Center and hit the Bluetooth icon, wait at least 30 seconds, then toggle it back on.
These often include bug fixes, even for issues that are not listed in the brief release notes, and thus should always be installed.
Go to Settings Reset Network Settings This will clear out all Bluetooth pairing of all devices, including every setting and configuration that has been made on the i OS device.
If you’re still holding onto the i Phone 4s it might be time to upgrade.