When you receive a chat, you are notified audibly with a sound notification. Sound notifications are enabled by default in Gmail and orkut. Of course, you can always disable them at any time. Here's how:
- Click the gear icon link at the top of any Gmail page, and open the Chat tab.
- In the Sounds section, select Sounds off.
- Click Save Changes.
- At the bottom of your chat list, select Actions.
- Under Enable sound click No.
Note: Disabling sound notifications in Gmail will not disable them in orkut automatically.