Voice messages don't use ear speaker when holding phone to ear

I have:

• searched open and closed issues for duplicates
• read https://github.com/signalapp/Signal-Android/wiki/Submitting-useful-bug-reports

Bug description

When playing an audio message and holding the phone to the ear only the volume changes but not the speaker used. Even if the media volume is set to zero, after triggering the proximity sensor the message can be heard.

Steps to reproduce

• receive a voice message
• push the play button
• hold phone to ear

Actual result: Message changes in volume and plays through the media speaker
Expected result: Message is played through the earpiece speaker

Device info

Device: LGE Nexus 5X
Android version: 8.1.0
Signal version: 4.16.9

Link to debug log

https://hastebin.com/kopiyenini

Possibly relevant lines from the debug log:

03-28 17:00:54.619 11906 11906 W MediaPlayer: Use of stream types is deprecated for operations other than volume control
03-28 17:00:54.620 11906 11906 W MediaPlayer: See the documentation of setAudioStreamType() for what to use instead with android.media.AudioAttributes to qualify your playback use case

Similar issues:

• #6673
• #6455

Start by reproducing voice-message playback on the reported Nexus 5X and review the linked debug log, focusing on playback and proximity-sensor behavior. Done means holding the phone to the ear routes the message through the earpiece rather than the media speaker, including when media volume is zero.