Similar thing Ben Burtt said about making sounds for Indiana Jones and the Crystal Skull (http://vimeo.com/channels/41219#3037441), where distorted sound gave “real” element to the sound.

This is the genuine sound that the shuttle makes and some theorize that it is caused by a vacuum and the air that rushes in to fill the gap, much like a thunderclap.

Obviously, inferior mike preamplifiers will distort this sound and it could easily sound distorted as the high frequency peaks are quite high (see the spectragram at digido.com) but I can assure you that they are VERY accurately recorded and not distorted on the super-clean recording which I have made.

Hope this helps.

Bob

“Think of it as an 8.3 GWatt amplifier/loudspeaker with
zero percent distortion and response down to DC!”

I wonder if the crackling sound has something to do with the distortions in the air itself due to the extreme (215dB)SPL? I read somewhere that above around 194dB, the rarefacted part of the wave becomes a perfect vacuum and thus clips the waveform valleys…

During the first Space Shuttle launch in 1981, acoustical pressure caused by the main engines / solid rocket boosters igniting was so great that it caused damage to the shuttle wing’s control surfaces.

At launch, the sound pressure level is: 215 dB (http://www.makeitlouder.com/Decibel%20Level%20Chart.txt)

Space Shuttle payload bay is rated for a maximum pressure of: 145 dB

The solution to prevent these high sound pressure levels from damaging future shuttles was to design a water based sound suppression system.
http://www.nasa.gov/mission_pages/shuttle/launch/sound-suppression-system.html
http://www-pao.ksc.nasa.gov/nasafact/count4ssws.htm

This system starts to unleash 1,135,620 liters of stored water 6.6 seconds before solid rocket booster ignition. The water flows through huge pipes and is sprayed below the rockets to help suppress the acoustical pressure. The water helps to block the reflected path of the sound so it cannot bounce back towards the shuttle. With the system in place the sound pressure is reduced to 142 dB, which is just 3dB below the design requirement.

To make sure the sound pressure levels from the engines are constant, they are occasionally measured. When the engines are test fired at the test ranges in Utah, NASA engineers wire the engine with microphones and place more microphones down range to record how much pressure is being outputted. Check out this “Daily Planet” documentary on testing the engines for sound and vibration (Sept 28, 2007):
http://broadband.discoverychannel.ca/discovery/?id=3539
(I love how fast the engine goes from OFF to ON. AWESOME !!)

And for a rocket engine test with some cool audio, check out this video of NASA’s new “methane” powered engine. (I love the drone at the end when the engine turns off…..)
http://science.nasa.gov/headlines/y2007/images/methaneblast/testfiring.wmv
http://science.nasa.gov/headlines/y2007/04may_methaneblast.htm

“Through the magic of Spectrafoo’s audio analysis tools, the audio “portrait” below demonstrates that there’s nothing like being there. The spectragram runs from T minus 4 seconds to about T plus 2 minutes. I don’t think there’s anything on earth that compares with the sound and sight of that fire-breathing monster on liftoff. If you study these incredible specs, including a spectragramic timeline of the liftoff, you will see that to do justice to the experience, you will need a low-distortion subwoofer system capable of producing up to ~119 dB SPL on peaks at 25 Hz and ~116 dB SPL at 16 Hz and below! If not, then you will not be able to feel the chest-thumping, clean solid bottom that is produced. Ironically, the shuttle liftoff from the VIP site is “just loud enough” in person, a pleasant and not ear-damaging experience. Think of it as an 8.3 GWatt amplifier/loudspeaker with zero percent distortion and response down to DC! Running at say, 40% efficiency, that would take 20 thousand megawatts from the breaker box! Those figures are calculated by Dick Pierce from the comparable Saturn 5 moon rocket. These are the figures at 0 foot distance. Of course, some power has been dissipated at 3.1 miles, but examine the astonishing figures below.

It turns out an LFE channel is not needed to reproduce this recording with a properly bass-managed system, because “bass” is the focus of this recording and it requires turning up the gain by 7 dB ABOVE Dolby standard. However, it could not be engineered to reproduce at Dolby Standard monitor gain without redirecting the bass to an LFE channel or it would overload the digital level. But then the bass would not be in stereo, and the shuttle definitely sounds better to me with stereo bass.”