The 64-bit version of ESO seems to have numerous audio problems.
The worst of them is a very loud & disruptive static noise (like you'd hear when tuning an old AM/FM radio) that cuts through all other audio every so often (maybe 1-5 minutes between repeats). Other problems I noticed were sounds playing at the wrong times, wrong volume levels or just abruptly cutting off, as well as the wrong music tracks (for example combat music in a non-combat area) starting to play at random and then stopping after 2-3 seconds.
I've experienced none of these issues after switching back to the 32-bit version of ESO.