Me podeis indicar alguna herrameinta para hacer este tipo de conversion, headac3 la hace sobre ficheros wav, pero plantea el problema de que no todos los wav le gustan, por supuesto descomprimidos claro, y muchas veces casca a medias.

Cualquier editor de audio decente lo hace. Cool Edit ( adobe audition ), Sound Forge, Wavelab, Goldwave, Awave...

Acabo de descubrir una herramienta gratuita que te puede servir.

CitarDescription
This utility program was designed to allow both amateur and professional users to perform high quality sample rate conversion of WAV files. For example, if your WAV file was recorded or saved as 48000 (or 96000) file and you need it to burn onto a CD you will likely need to convert it to 44100 before that. This utility will help you to perform such conversion. r8brain also supports batch processing which is essential if you need to transfer all your project's audio data from one sample rate to another. Programmers can use standalone converter DLL in their programs free of charge.  

Features
Freeware
Reads PCM WAV files of bit depths 8, 16, 24, 32 and 64
32 and 64 bit files can be in IEEE floating sample format
Mono and stereo file support
Virtually any input and output sample rate
Batch processing
Writes 8, 16 and 24 bit PCM WAV files and 32 bit IEEE WAV files
Reusable royalty-free converter DLL with explained API

Aquí:
https://videoedicion.org/foro/index.php?topic=1712;start=msg47315#msg47315