Hello,
Recently I have been unable to hear any sounds from the editor. My headphones work, but no sounds are coming from the game. I’ve tried restarting the editor and playing other projects but there is no sound in any of them.
Check if you have probably disabled the ue4 sound in your windows sound settings. Otherwise take a look at this thread: https://answers.unrealengine/questions/80710/i-seem-to-have-disabled-all-sound-no-idea-how-to-g.html 
"I actually had this problem too, and I’ve been waiting to post until I could find out how to solve it. It turns out there are two separate problems to consider here.
If you're using 7.1 surround sound, XAudio is failing to initialize and so you'll have no sound. This should be fixed in the 4.4.1 build - update and you should be hearing glorious sound again!
If that's not the case, you may have the same problem I had. Check your UE4EngineConfigWindows folder. If the folder is empty, that's a problem! You should place the attached .ini file in that folder (you'll have to unzip it first), and that should fix it if you rerun the engine.
If these don’t solve your problem, let me know! I’ll keep working on it until we figure this out."
Ok, I downloaded one of Epic’s projects from the marketplace, and the sound works in that, so I guess it is just my project. I tried searching for UE4EngineConfigWindows and it doesnt seem to exist.
Hello,
have you a distance set on thoses sounds ? Sounds are heard from camera, not character, so it may be the reason why you don’t ear them.
Its a first person game with the default gun, so there should be a sound when the gun is shout. Also, if I right click one of the sounds in the content browser and click play, no sounds are heard.
Ok :-(. At least, if you haven’t too much props, you may can create a new fps project, check that sound is ok and migrate (if we can’t find better solution)
As i had some troubles with last version : Was it a project upgraded from older version ? I had issues in this case and when i just migrated stuff to new project it worked fine.
No. 
I’ve been working on it for quite a long time… and it hasnt been upgraded from any previous versions.
Hi Noah,
What version of the engine are you currently using?
I’m running 4.4.3.
If you use 4.4.3 engine version and you work on this project since a long time so you began it on an older engine version, what i meant by saying that the upgrade may be the trouble you have like i got. Personaly, i did one large folder migrate and it was fast and then i no more had my bug.
No, I started the day after 4.4.3 came out, and I’ve been working 8-9 hours everyday since then.