In Wwise, the process of generating selected SoundBanks will assemble each connected Audio Source into the the corresponding Soundbank after conversion. Therefore, the size of the SoundBanks solely depends on what audio format the Audio Sources are being converted into. For mobile games it's very common for produces to set a size limit, and as such, you will often have to use a compressed audio format for at least some of your Audio Sources to get the SoundBank sizes beneath the limit. As all Audio Sources will have to be decompressed into PCM before being sent to the system output every time a sound is called, this will result in a higher CPU usage for compressed Audio Sources like Vorbis than the uncompressed PCM audio format. Fortunately, there is a way to reduce CPU usage in runtime by simply decompressing all the compressed Audio Sources in the SoundBanks once the SoundBank is loaded, which means that the Audio Sources will not have to be decompressed in runtime.