Since the Sony Xperia Z5 family was updated to Android Nougat a month ago, we have received a steady stream of complaints from users regarding low in-call volume, headphone volume and an imbalance of the top and bottom speakers.
The good news is that Sony has confirmed a fix is on the way, with a new firmware update due in mid-April 2017. In the meantime, if you are suffering this problem, then a possible workaround is to factory reset your phone, although this doesn’t work for everyone. Please find the statement from Sony below.
Sony Mobile statement on low in-call volume issues for Xperia Z5 users running Android Nougat
“This will be fixed in an upcoming software update planned for release in the middle of April, 2017. In the meantime, a workaround is to perform a factory data reset. Please make sure that you backup data stored on the internal storage that you want to keep before performing a factory data reset. I’m sorry for any inconvenience this causes.
“The speaker calibration starts the first time you are using the speaker, and later requires that the loud speaker is idle for 30 minutes. The calibration is completed after up to ten hours.”