This has been something I've experienced in many versions, including 1.12 (which is the earliest version I've played other than historical versions from like 2009 that I've tried for fun). When you leave the game open and don't do anything for a long time (for example 5 hours) all sound will disappear even after changing volume settings on both game sound and device sound. The sound comes back after either restarting the game or changing a texture pack. I haver no Idea if this has been reported before but I tend to experience this often when going afk in servers, singleplayer in pause menu, or the title screen. 

This usually happens when I turn in game sound to 0% via the music and sounds menu, go afk for a few hours, come back and set in game volume to 100% but find it not working. This is resolved in 1.18 as the new sound device toggle setting is in these snapshots. 

What I expected to happen was...:
Everything would be normal and sound would never stop working.

What actually happened was...:
All sounds of any kind stop working after a long time of having the game open. 

Steps to Reproduce:
1. Open the game in full screen(it probably still does this in windowed but I always play in full screen) and leave it running for a few hours (try between 1 and 6 hours). Don't do anything in the game during this time
2. Come back and try making sounds by clicking things or making sounds such as footsteps or block breaking in a world/server. There should be no sound if you have waited long enough. 
3. If there is no sound, change texture packs by taking off, putting on, or swapping any texture pack. Or f3+t to reload texture packs. The sound will work again.