I also am experiencing white noise at a constant volume except when the volume is muted.
I have tried changing PCM settings using alsa-mixer but this did not work.
The problem can be replicated by simply booting the 64bit Ubuntu 11.04 desktop LiveCD on a Samsung R540-JA04UK laptop.
Happy to help if there is any more information I can provide.
I also am experiencing white noise at a constant volume except when the volume is muted.
I have tried changing PCM settings using alsa-mixer but this did not work.
The problem can be replicated by simply booting the 64bit Ubuntu 11.04 desktop LiveCD on a Samsung R540-JA04UK laptop.
Happy to help if there is any more information I can provide.