Sound Suppression System

Launchpad Water Sound Suppression System Tested for Ares
You know all that water they dump on the launch platform when a rocket takes off? Seems it reduces the amount of noise from the rocket engines reflected back at the rocket, specifically the space shuttle. The shuttle engines made so much noise it actually inflicted some damage on the SRB-s (Solid Rocket Boosters). Minor damage, but still, not something you want to happen. NASA has a page about it.
     The water also helps reduce the amount of damage that the rocket blast inflicts on the launch platform. Stack Exchange explains why the Russians launch their missiles over a pit:

"Russians for the Soyuz boosters have an interesting approach that does not use water suppression, since Baikanour is often experiencing winter when they wish to launch, when flowing water won't work so well (and snow is not as effective as water for this task). They basically suspend the booster over the edge of a cliff, so that the exhaust goes down, and then out a vent, such that there is not much infrastructure directly below it to be damaged."

I had never heard of the 'Sound Suppression' angle before. I thought it was all about ameliorating blast damage. Huh. Learn something new every day. Previous posts about Baikonur.