Bassey sound before going on stage?

[SoyMilkHero]

I went to a Tool concert recently and noticed that before they went on, there was a really really loud bassy sort of noise, but i don't think it was in instrument...it was just a constant kind of roaring. Anyone know what it is?

 

[kalle74]

intro tape, engineers checking the PA system low-end response with noise, crowd noise, background music...? All possible...

 

[Stumbo]

or hum....mmmmmmmmmm

 

[bongomania]

Could have been feedback, or a recorded sound to test the speakers or wake up the audience.

 

[sonic assassin]

pink noise to test the subs? likely WAY too loud

 

[Arpeggiator]

a similer thing happend at a festival i went to a few days ago problem was this was during the bands set. stupid engineers turned the bass up too LOUD *shock horror*