Does my 9 week old need a different teat ??

I used Avent No 2 with my 17 week old daughter and had to change the teets- they were too big and difficult for her to manage, and she ended up sucking down a lot of wind with her food because she wasn't able to clamp down around the teet correctly. The noise you are describing is wind in her stomach, my baby was the same until I changed her teets. Give it a go and see what happens :).