Based on this forums thread: https://www.tt-forums.net/viewtopic.php?f=31&t=87257

Version of OpenTTD

Unknown (probably most)
Windows 10

Expected result

Putting the computer to hibernate while the game is running, then resuming the computer, the game continues to be able to play sound.

Actual result

After resuming the computer from hibernation, sound effects are no longer audible until the game is restarted.

Steps to reproduce

1. Start game
2. Ensure sound effects are playing
3. Put the computer into hibernation mode
4. Resume the computer from hibernation
5. The game continues working except sound effects are no longer audible

This likely depends on the exact audio device used, and perhaps also which other audio devices are available in the system. The original reporter is playing audio via a display cable, i.e. an external digital device which might have some re-initialisation required after a resume operation.
It's likely that reproducing this issue requires having a similar external audio device, and possibly having no other active/functioning audio devices that the system can fall back on.

This might depend on the sound driver selected in the game. It's possible that only one of the XAudio or Win32 drivers will exhibit this.