Is it one of the ones with the seperate mic cable, or is audio
expected to be driven through usb too? If everything's through usb,
you'll probably need specific drivers for the audio ... let's see what
Google throws up? What's the webcam model?

Got to [ System / Preferences / Sound / Input ] and select the web cam
microphone in there. Similarly if using Skype you need to select the
correct sound input device in Skype preferences.

The microphone is usually muted in the mixer panel by default. Click on the
speaker icon in the system tray and choose Sound Preferences. Click on the
Input tab and check to see if it is muted. If so, unmute and try your camera
again.

My system tray speaker icon disappeared when I upgraded to 10.04
64-bit (Gnome-based) ...

Open up the terminal and type in
aslamixer
That is the master control of all sound in and out. Use the tab key to select
volume and the up and down arrows to select levels. Talk into a mic or a pair of
head phones. Yes, head phone work as a mic when plug into the red circle on your
sound device. Speakers of any sound system will do the same. If you want to
record some on with out notice for example. You can turn your home speakers into
a mic.
Any ways. Keep on saying test or what every on your mind. Tell you hear it.
Of that does not work. There is other things we can trouble shoot.

First of all try not to hijack other threads, start a new one for a
different question - you risk not having your message read if it's
buried in a thread not related to the question.

Next, Right Click on any blank part of the top panel and select 'Add
to Panel' then select 'Indicator Applet' from the list.

My system tray speaker icon disappeared when I upgraded to 10.04
64-bit

Thank you very much, it works now........