You can enable, disable or change notification settings for messages you receive in Hangout for Android. Just follow these steps.
1. Open the Hangouts app.
2. From the screen where you have your list of friends, press the Menu button.
3. Tap Settings.
4. In the Hangout Notifications area, you have a few options:
- Notifications – Controls whether you receive a notification at all. Uncheck this box if you don’t want any type of notification including sound or a message in the notification bar. Check it if you’ll be using some type of notification.
- Sound – Set a custom ringtone or silence the notification sound.
- Vibrate – Device will vibrate when a message arrives.
- Hangout request – You’ll receive an alert when a new hangout is requested.
Be aware of the settings in the Video Calls section as well. You’ll have the same Notifications, Sound and Vibrate options as above for video calls.