How to debug microphone?

[Felix Natter <felix.natter@smail.inf.fh-brs.de>]

hi,

I'd like to use my microphone, but when I use gnome-sound-recorder, and
- select "Record from input: Front Mic" it doesn't record anything.
- select "Record from input: Line In" and attach a headset to the 3.5mm
  mic input (Laptop) it doesn't record anything.

Audio play works fine in all applications.

I am running Debian Lenny. How can I debug this?

Thanks!
-- 
Felix Natter