I've been having the exact same issue with sound since 1.4 hit, certain sounds just randomly stop playing, as pointed out earlier lack of mount noises is the really noticeable sound that draws you're attention to the problem. The only workaround I’ve found is to restart the client.

I’m using an Asus Phoebus soundcard with the latest drivers connected to set of Razer 7.1 Tiyamat's.

Hey there @Babylon,

We're still looking into it. It's likely something that's going to need a patch fix. The devs are aware of it and are hard at work. We appreciate your patience as well as the additional information.

Same sound problems for me, but when i get this, in auridon, glenumbra, craglorn or any other place i only get sound back if i enter a building, dungeon or any other palces that make sound diffrent than you are, fex, if i run/walk in water i do hear some sound from footstep but when i reach land the sound are gone. then i can go inside a tent, dungeon or house and the sound comming back. this happends only one time per inlogg, so if i switch char it can hapend but if i switch back the sound are all good. repair, delte txt or any other tip dont work for me.

Hmm,
"Fixed an issue where you could lose the sounds your character makes after fast-traveling to Cyrodiil."
My char's never went to Cyrodiil, since the 1.4.3 patch anyway. I think this "fix" didn't. That said, I haven't had the problem either. Time will tell.

When certain sounds disappear, usually walking into a building returns the sound levels back to normal, and it doesnt have to be a building with a door it seems, for example, when your sound disappears, Walking into the stable building in Rawlkha returns the sound for me, and this building does not have a door.

Still not fixed. This is pretty sad.