Spectrum from Falcon Heavy recording, above:
About -20dB/decade from 10 to 1000Hz, then -30dB from 1k to 10kHz.
I'd wager it doesn't really roll off below 10Hz as shown.
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Acoustic/infrasonic rocket engine signatures
https://ui.adsabs.harvard.edu/abs/2003SPIE.5090...30T/abstract
Infrasonics offers the potential of long-range acoustic detection of explosions, missiles and even sounds created by manufacturing plants. The atmosphere attenuates acoustic energy above 20 Hz quite rapidly, but signals below 10 Hz can propagate to long ranges. Space shuttle launches have been detected infrasonically from over 1000 km away and the Concorde airliner from over 400 km. This technology is based on microphones designed to respond to frequencies from 0.1 to 300 Hz that can be operated outdoors for extended periods of time with out degrading their performance.
About -20dB/decade from 10 to 1000Hz, then -30dB from 1k to 10kHz.
I'd wager it doesn't really roll off below 10Hz as shown.
---
Acoustic/infrasonic rocket engine signatures
https://ui.adsabs.harvard.edu/abs/2003SPIE.5090...30T/abstract
Infrasonics offers the potential of long-range acoustic detection of explosions, missiles and even sounds created by manufacturing plants. The atmosphere attenuates acoustic energy above 20 Hz quite rapidly, but signals below 10 Hz can propagate to long ranges. Space shuttle launches have been detected infrasonically from over 1000 km away and the Concorde airliner from over 400 km. This technology is based on microphones designed to respond to frequencies from 0.1 to 300 Hz that can be operated outdoors for extended periods of time with out degrading their performance.
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