![]() For sea level air at a typical ambient temperature he computed a value of 979 ft/sec, which is too low by about 15, the true value being about 1116 ft/sec. To be fair, it was explained that the wind and weather conditions were unfortunate, as they favoured the propagation of sound, but in any case a sonic boom is way too loud to be done for fun: it's only allowed in case of emergencies.īy the way, in the end it turned out it was a false alarm, so at least there was a happy ending. The Speed of Sound The first analytical determination of the speed of sound was given by Isaac Newton in Proposition 49 of Book II of the Principia. The result? Among other things, there were hundreds of calls to the police, people ran out of buildings in panic, some schools and offices were evacuated, and some windows got broken.Īnd at an airshow they'd fly much lower, so it would be louder! And at first they were mistaken for bombs. The sonic booms were heard from Aosta to Bergamo, which are 180 km apart. Two Eurofighter Typhoons were sent to investigate, and as they rushed there they broke the sound barrier. On 22 March 2018, Air France flight AF671A from Réunion to Paris Orly was flying over northern Italy when it lost radio contact with Air Traffic Control. Let me give you a practical example of what a sonic boom did in a radius of 100 km. John K has already provided an example of what a sonic boom feels like from very close, and Harper - Reinstate Monica describes it in general terms. The writer was warned in no uncertain terms that if he didn't protect his ears he'd get hearing damage, and not to be fooled by the initially silent passage of the jet itself into taking his fingers out of his ears. All the glass of the cars at the speed traps blew out and their trunks popped open. The F-104 passed over the car at the 1st speed trap at 60 ft AGL and passed the writer in absolute silence, and it wasn't until a second or so had passed that a sound like a dynamite explosion a couple hundred feet away went off. I remember the description of the event by the writer who witnessed it from somewhere along the middle of the course, a safe distance away with other observers. This explains why the answer of 333 m/s is slightly above the accepted value for the speed of sound in air.Just for a bit of flavour, I recall an article from Air Progress from the late 70s about Darryl Greenamyer setting the low altitude absolute speed record, in his "homebuilt" F-104, of Mach 1.3 (mentioned in this article) in 1977.įor the run he had to cross very low over timing trigger devices at the start and end of the speed course at the dry lake bed at Edwards, which were set up with cars parked beside them. The values recorded will be dependent on the reaction time of the observer, and will not be entirely accurate. One person might stop the timer a fraction of a second later than another person. However, this experimental method is flawed as humans do not use stop clocks identically to one another. The accepted value for the speed of sound in air is 330 m/s. distance ( s ) is measured in metres (m)Īn observer 400 m away records a 1.2 s time difference between seeing the hand signal and hearing the bang of the starting pistol.speed ( v ) is measured in metres per second (m/s).The speed of sound can be calculated using the equation: A distant observer stood 400 metres (m) away records the time between seeing the action (the light reaches the time keeper immediately) and hearing the sound (which takes more time to cover the same distance). For example, a person fires a starting pistol and raises their hand in the air at the same time. Light travels much faster than sound through air. The vibrating particles pass the sound through to a person's ear and vibrate the ear drum. When sound is created, the air particles vibrate and collide with each other, causing the vibrations to pass between air particles. The air is made up of many tiny particles.
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