Sony will release a software update to fix the low volume issue during calls on Xperia Z5 series devices.
Following the rollout of Android Nougat in January a number of users reported the low volume during incoming calls Sony Xperia support forum.
"Because I updated (clean install) my Z5 to Nougat (32.3.A.0.376) yesterday, but today I have had to downgrade to Marshmallow because I almost did not hear other person during calls (sound level set in maximum during call) and also while listening music viac phone's speakers the sound was very low (also sound level set in maximum during playing music)!" a user wrote on the forum.
"Same problem. After updating to Android 7.0 the music from my music app Poweramp got barely audible with the max volume. I tried other apps with the same result. There's just no sound. Same happens when I want to play a video. The problem started right after updating to Android 7.0. I have a SonyXperia Z5 Dual Premium" noted another user.
Sony has already acknowledged the issue and said an update is coming in mid-April. But if you cannot wait for the official fix, as a workaround you can try performing a factory reset, which may resolve the problem.
In a statement issued to XperiaBlog Sony said: "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."