When starting snapshot 17w43a, there is no sound. Version 1.12.2 (and other versions) work fine. The launcher logs that files are missing, as follows;

Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release
[01:52:20] [Client thread/INFO]: Setting user: <<<NAME REMOVED>>>
[01:52:22] [Client thread/WARN]: Skipping bad option: lastServer:
[01:52:22] [Client thread/INFO]: LWJGL Version: 3.1.2 build 29
[01:52:23] [Client thread/INFO]: Reloading ResourceManager: Default
[01:52:23] [Client thread/WARN]: Missing sound for event: minecraft:ambient.cave
[01:52:23] [Client thread/WARN]: Missing sound for event: minecraft:block.anvil.break
[01:52:23] [Client thread/WARN]: Missing sound for event: minecraft:block.anvil.destroy
[01:52:23] [Client thread/WARN]: Missing sound for event: minecraft:block.anvil.fall

(snipping 544 lines, showing the same message for - presumably - all sounds)

[01:52:23] [Client thread/WARN]: Missing sound for event: minecraft:weather.rain.above
[01:52:23] [Sound Library Loader/INFO]: Starting up SoundSystem...
[01:52:24] [Thread-2/INFO]: Initializing No Sound
[01:52:24] [Thread-2/INFO]: (Silent Mode)
[01:52:24] [Thread-2/INFO]: OpenAL initialized.
[01:52:24] [Sound Library Loader/INFO]: Sound engine started
[01:52:26] [Client thread/INFO]: Created: 1024x512 textures-atlas
[01:52:27] [Client thread/INFO]: Narrator library successfully loaded
[01:52:27] [Client thread/ERROR]: Realms module missing
[01:52:33] [Client thread/INFO]: Stopping!
[01:52:33] [Client thread/INFO]: SoundSystem shutting down...
[01:52:34] [Client thread/WARN]: Author: Paul Lamb, www.paulscode.com
AL lib: (EE) alc_cleanup: 1 device not closed

I have tried completely reinstalling, with the same effect. There are no other errors; all files seem to have downloaded correctly - I can manually browse/locate the sound files and play them.

Narrator works as normal, making sound. The /playsound says it plays sounds, but does not make sounds. F3 and T has no effect.

I also tried the newer launcher (from http://launcher.mojang.com/staging/) and got exactly the same results.

I removed everything (deleted .minecraft), reinstalled and rebooted between these attempts. Other versions work (1.12.2, 1.11.2, 1.10.2, 1.9.4), whether installed before or after this one. I tried (separately, fresh install again) adding a resourcepack which contained sounds, which had no effect.