ok so I searched esoui for that function to see if there was something already written I could test.
Turns out there was an addon written in 2015 that handles this for you
Just install this:
into your you /documents/Elder Scrolls Online/live/AddOns
and then go into your keybindings and scroll down until you see Audio Doctor
What you are looking for is called "footsteps" just toggle it off and goodbye annoying mount noise. You can also use these functions to toggle and turn down individual layers of the audio, it works as of today may 2018 on the PC NA server.
Well I had a crap load of crown gems laid about, so I bought the Dwarven Horse, think it looks great but man, when you gallop it sounds like a bunch of rampant honeymooners on a 70 year old bed.
That squeaking makes my teeth itch, I have a permenantly ruptured eardrum and the pitch of the squeaking makes it sound like the old fingernails down a blackboard thing.
Could I say, take a copy of the sound file for another horse and rename it so the game would use it for the Dwarven Horse ? Or is it bad doo doo to swap game files round etc ?
...keybindings and scroll down until you see Audio Doctor, "footsteps" just toggle it off and goodbye annoying mount noise.