Silence a PVC overflow?

[Mistablik]

I just got done making a PVC overflow. ( http://youtu.be/66Rr2SQv-cc )The overflow makes a lot more noise than I would like. The most annoying one is in the actual sump itself. The outflow tube from the overflow seems to carry bubbles along with the water causing it to gurgle into the sump under the tank. The second sound is coming from the waterfall when the water enters the overflow (the pipe that sets the level.) The third sound is a slightly less annoying gurgling sound coming from the standpipe on the back of the sump.

Do you have any ideas on how to silence these?