i just dont want my audio format changing ... i capture in final cut pro 5.1.
Final Cut - and, for that matter, most audio editors that I'm aware of - will only work with uncompressed sound. This is because it is expected that you will want to change the content in some way, whether by changing levels, mixing tracks together, or equalising/treating the source recordings. This is not possible with compressed sound: it is really just designed for playback, and uses quite serious acoustic masking techniques. The same does not apply to frame-based compressed video (like DV or HDV), where you can leave it as is while editing for a lot of the time.
Are you sure that your camera doesn't record uncompressed sound as well as the .mpeg1? If so, it would be natural for FCP to transfer this, and ignore the compressed version. Alternatively (if it doesn't) the sound is being converted to an uncompressed format on the fly so that you can edit it.