The human ear can hear down to 20 Hz and I was wondering if anybody knew if a tuba could play that low or, if not, how low a tuba can play.

You can work this out as follows:

440Hz (Hz=Hertz the unit of frequency) is the A above middle C (the usually "tuning note" for orchestras) and the Bb above is therefore approximately 466Hz. As today's standard scale has an equal temperament ie 12 increments on a logarithmic scale doubling every octave- see http://en.wikipedia.org/wiki/Equal_temperament

The lowest open note on Bb Trumpet/cornet is an octave below ie approximately 233Hz.

The lowest open note on Bb Euphonium is a further octave below ie approximately 116Hz.

And the lowest open note on BBb Bass is a further octave below ie approximately 58Hz. I've avoided pedal notes which are a further octave lower and approximately 29Hz on a BBb Bass. In principle, a very good player could descend a further half octave using the standard valves ie down to approximately 20.5Hz. Other tubas can't play this low eg a EEb tuba is a 4th higher ie frequencies are higher by a factor of 1.3348.

i HATE math class we are doing algera now and it hurts

theres a instrument called a tubax, its a sub contrabass saxaphone 8 feet hight with 28 feet of tubing. it can play the space below the 8th leger line and can be tuned to play too low for humans to hear