Sounds are never reloaded or freed

[slipher]

Once a sound is loaded, it is kept in memory, including across cgame restarts. This makes the game load new levels faster, but it is not good for correctness. This means that if a mod tried to customize a sound, it wouldn't work correctly. Whichever version of the sound (vanilla or modded) loaded first would be cached forever. A different version of a sound can only be reloaded following a restart of the audio subsystem. This normally never happens unless the user explicitly requests it.

Additionally, some sound objects are never freed, even if the audio subsystem is restarted. The destructor of Sample never seems to be called (see also #422, #899).

[cu-kai]

I seem to remember this happening on Tremulous, if you joined a modded server then joined some other server, you'd still be using the sounds from the modded server even if sv_pure was enforced.