reminds me of a story I read about simulating the noise from a space launch (or something similiar - it was loud whatever it was)..
they built an enormous vertical horn firing straight down and tried it, but it wasn't loud enough.. IIRC they then did something to the drivers or amps to make it louder again, but still no-where near being loud enough.
in the end they filled it with gas and ignited the gas from the top, effectively horn-loading the explosion!!

fun stuff