Recorded the sounds of space launches hitherto impossible to perceive for the human ear. They have been detected thanks to the recordings of about a thousand launches, from those of the Space Shuttles to those of the Chinese Long March, from the SpaceX Falcon 9 to the Russian Soyuz rockets. The recordings were made by the network of more than 50 detection stations, the International monitoring system (IMS), created following the 1996 treaty for the banning of atomic weapons, the Comprehensive Nuclear-Test-Ban Treaty (Ctbt ). This is what emerges from the study published in the journal Geophysical Research Letters, coordinated by researchers from the German Federal Institute for Biosciences and Natural Resources in Hanover.
The recorded signals, experts explain, are infrasound. That is, they have a frequency of less than 20 Hertz, therefore below the hearing threshold of the human ear. The sound waves, the authors of the study specify, "have been speeded up by 250 times, so as to be audible even by humans". The researchers hope that recordings like these will allow them in the future to assess the success of individual rocket launches and identify any problems. In the event of failures in the delicate launch phase, they conclude, "infrasonic signatures could, in fact, help to understand what could have gone wrong".