Source: http://world-of-ru.livejournal.com/3552084.html

Hello everyone,

Wargaming decided to switch the game sound engine to Audiokinetic Wwise, first in World of Warplanes (current 1.6 test), then in World of Tanks. The reason for this change is to allegedly introduce more stable and effective sound engine. That however means one thing: from that point onwards, all sound mods (engines, gun shots, music etc.) will stop functioning.

It is unclear whether the mods will be possible to rework under the new system, it allegeldy has nothing in common with the original FMOD. Freeware version of the engine is apparently quite limited and the full one starts at 150 USD, so it’s possible the mod makers (even if they can do it) will find it too much of a hassle.