I grew up next to a rail track and always wondered why friends who came over to play looked startled when a massive freight train would shake the house. Currently I live close to an airport and my guest are running to window to see whether that plane actually hit our building or not.
I hardly notice anything. The brain - in a form of self defense - is filtering out the noise.
The same is true in presentations. Endless bullet points, cliche language, we heard it so often that the audience is filtering things out. Speaking louder or using bright colors does not really help. Try to be different/original and people will start paying attention again.

If you liked this post, why not subscribe to daily updates about presentation design via email? Just blog posts, no spam, or you can follow Jan on Twitter to never miss a thing.