What do extremely low notes sound like?

[jbaylies]

I'm curious since I've never heard a recording of any extremely low note played on the tuba. I can play the pedal Bb & I know it's just thudthudthudthudthud, but once you get down into the double pedal range are the thuds the same length as they are when you hear them in a pedal Bb or are they more drawn out? In short, what does one of the thuds in a double pedal Bb sound like?

thud thud thud OR thuuud thuuud thuuud

(also, search doesn't work for me, if this is a double post, sorry.)

[Wyvern]

It sounds like the low rumbles I have heard from elephants while on safari in Africa. A good party trick, but not what I would call a musical note