Presentations and Posters ⇒ sounds in beamer with different sampling rate

[lingrand]

I'm writing a presentation using beamer and the package multimedia in order to include sounds. I'm using okular under linux to display the presentation.
I have different sounds in wav format but at different sampling rates. I can play these sounds correctly using external players such as mplayer. In the presentation, there is no problem with sampling rates above or equal to 4000 Hz using \sound command.
Sounds of sampling rate are still working at 2000 Hz using \movie instead of \sound. But I'm unable to play sounds of smaller sampling rate even if I specify the sampling rate as optional field in \sound command.
Does anybody know where this should come from ? multimedia package ? options in sound command? pdf viewer configuration ?

Thanks !

Diane