While you doing important stuff's you will forget to see the chats in Gmail box. You can enable sound notification in Gmail while you are performing another stuff's . You are notified audibly with a sound notification,while you receive chats in Gmail. Sound notifications are enabled by default in Gmail you can always disable them at any time.
I will show both text and video to Enable/Disable sound notification in Gmail .
1.Open your Gmail account and click the gear icon present at right of your Gmail
2.Click the setting displaying below the gear icon .The setting will be opened .
3.Now click the chat tab .
4. In the sound section
select sound on, if you want to turn on the sound
select sound off, if you want to turn off the sound
5. Click save changes .
NOTE:You must have Flash enabled on your computer to use sound notifications in Gmail.