Patch 4.3.3 has brought some changes to the sound engine in WoW.
The most obvious is that sound replacements now have to be in OGG format exclusively, WAV files aren't considered as valid anymore [source]. This means that a lot of sound replacement addons might not work anymore out of the box.
The second, more subtle change is that the sound files now actually need a content. In the previous versions of my Muted Sounds Addon, I was using literally empty OGG files to replace the sound. They were valid OGG files (i.e. not zero-byte) but contained no sound whatsoever. This worked fine until the patch hit, but after that I had multiple sound dropouts (boss emotes, addon sounds, etc) that didn't happen before.
After some trial and error it turned out that I needed to insert 1ms of silence to make the sound files work again correctly.
- You now need (only) valid OGG files to replace sounds.
- .wav files simply renamed to .ogg will not work.
- Neither will files with a length of 0 (empty dummy files, e.g. an empty .txt file renamed to .ogg).
- These valid OGG files require an actual content. 1ms will do.
This may not be a problem when you only want to replace a few files, but at least for a large number of files (24,500 for my addon) it definitely is.
Also, if anyone could inform the poor blokes in the US forum about this, they haven't seem to found the answer yet, and I cannot post in the US forums.