Sun audio encoding

[Loek Raemakers]

I want to play a sound by using AudioClip.
The sound I converted to the sun .au format.
I used different sound.programs [i.e. CoolEdit] but I can not play my sound.
There is a problem with the conversion.
I get the message:

NativeAudioStream: invalid audio encoding.
NativeAudioStream: invalid file type.

What is wrong?
Is there a simple program that does what it should do; just convert one format
( .mp3 or wav) to the .au sun format?
Do I have to edit the first 2 lines of the sound files 'by hand'?

Thanks, Loek eR