Converting mp3 to caf file for iPhone

I am experimenting with the sampling rate of the mp3 file to convert it into caf format. afconvert -f caff -d LEI16@44100 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@22100 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@12000 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@20100 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@15100 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@14100 ./fricatives开发者_开发问答_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@13100 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@44100 -c 1 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@13100 -c 1 ./fricatives_play_all.mp3 ./test.caf afconvert -f caff -d LEI16@22100 -c 1 ./test ./test2.caf

I have used different sampling rates as above for converting mp3 files to caf files. For instance, for a 38.5 MB file :

Sampling Rate Size 15,100 72.6 MB 14,100 67.8 MB 13,100 63 MB

As you can see the file size reduces with the lower sampling rate but the quality gradually decreases. If you could provide more insight into this problem, I would really appreciate it.

If it's a stereo file, you could convert it to mono. You can also use the IMA-4:1 compression, which reduces the file size to 25%, but it does reduce the quality somewhat.