Sample Frequency and bit rate chaning

["Jack"]

Hi all
I was wondering if you can help.
I have about 40 voice files (in mp3, wav and ogg format) all of them about 6
or 7 sec in length.
the sampling freq. is 22050 and bit rate is 16.

Is there any way I can change the Sample freq. to 16000 and bitrate 8.
without losing quality of sound.

I have tried audacity but the sound changes into like COW. :)


any ideas.

Jane