When somebody you follow on Twitter make a new tweet, you get an popup in your screen and a sound. When your working with other things, this can be very anoying.
This is the way to turn this new tweet notification off.
1) Start tweetdeck
2) Go to the settings icon on the right corner
3) Go to notifications
4) Click on detail and you will see the message detail off
5) Click on summary and you will see the message: summary off
6) Move the sound slider to the left, no more anoying sound anymore.
7) Click on save settings.
You are done.