Secret Sounds of Rocket Launches That Humans Can't Hear

The sounds of Rocket launch are, of course, loud and noisy, but all sounds that they make are not audible to human ears. Because when the rocket leaves the ground, it produces infrasonic – low-frequency – sound waves, which require special instruments to hear and detect.

And to know about them in detail and how they can contribute to a successful rocket launch, researchers have conducted a new study which includes the infrasonic sound waves from 1,001 rocket launches, including the Space Shuttle, Falcon 9 rocket, Soyuz rocket, Ariane 5, Russian Proton rocket, and Chinese Long March rocket. 

These recordings were made using the International Monitoring System (IMS), which is the result of the Comprehensive Nuclear Test Ban Treaty of 1996, consisting of more than 50 monitoring stations around the world. The network is specially constructed to detect nuclear explosions and can also detect the sounds of rocket launches well. 

You can hear the sound of one of the rocket launches in the video embed below – Space Shuttle Atlantis launched from Kennedy Space Center in Florida on November 16, 2009. Here, the sound waves are accelerated 250 times so that humans can hear them.

The instruments used by IMS have been tuned to identify the various stages of each rocket launch in some cases, although because these rockets travel faster than sound, in the example above, you will hear the help before the roar, splashing in the ocean to take off. 

The researchers hope that such recordings of the sounds of rocket launches will allow them to assess the success of individual rocket launches and identify any problems that may occur along the way. In rocket launches that did not go as planned, infrasonic signals can help scientists discover the cause. 

These infrasonic sound waves can travel a great distance and the IMS network can even detect them 9,000 kilometers (5,592 miles) away. 1,001 rocket launches were recorded as part of 7,637 infrasound signatures captured and analyzed at IMS stations from 2009 to 2020.

The 4,444 researchers were able to identify the infrasonic characteristics in 733 samples of the sounds of rocket launches, which is slightly higher than 73%. The remaining thrusts are too small to be recognized or are launched in atmospheric conditions that do not allow sound waves to propagate in sufficient detail. 

Adrian Peter, professor of computer engineering and science at the Florida Institute of Technology, was not directly involved in this research but had previously studied the infrasonic characteristics of rockets. Peter said that he is very happy to see that IMS is being used for other purposes and that the data collected may have many different applications in the future. 

“Now we use it for other scientific applications,” said Peter. “The ability to detect different types of sounds of rocket launches can be useful.”


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