Audio Compression

I am creating a game that uses a lot of sound bites (15M of mp3). Apple best practices talk about compressed formats. If I use “afconvert -f AIFC -d ima4 sound.wav” to compress any of the files, I get one almost four times the size. Can I use mp3s? Is there another way of compressing files, or am I doing something wrong?

Try CAF files

afconvert -f caff -d ima4 yourfile.wav