Eli5: Why does a sonic boom occur when you break the sound barrier?
In: Physics
Thanks everyone for the awesome answers. I figured it had something to do with the physical object vs the waves it caused but wasn’t sure how it happened
A sound is a wave traveling through the air. If you’re traveling through the air, the sound races out a head of you, traveling at the speed of sound.
If *you’re* traveling at the speed of sound, it can’t get ahead of you because you’re keeping up with it. But you’re also generating more sound. So all of that sound is just piling up on top of itself until you get a nice big boom as you’re passing through that wall of built up sound.
Why is it that UFO’s accelerate away at amazing speeds but never break the sound barrier ? No sonic boom ever !
You know when a fire truck or ambulance is coming towards you, the siren is higher pitched, but when it moves away the sound becomes lower? This is called the Doppler effect – the source of the sound is moving. As such, the sound waves become “bunched up” in front of the vehicle – the distance between the waves is smaller, creating a smaller wavelength, resulting in a higher sound. The reverse is true behind the source of the sound – a wider gap is created between the waves, meaning a greater wavelength, meaning a low sound.
A supersonic jet breaking the sound barrier means that it is going faster than the speed of sound – that is, the source of the sound is so fast, it catches up with the sound waves ahead of it. The resulting buildup of energy releases in the form of the sonic boom – the air particles in front of the jet collide with each other.
I hope that this was useful, and that my terminology is accurate and scientific – this is about all I can remember from all of physics at secondary school!
Also, the crack of a whip is actually a miniature sonic boom. As the whip is flicked, the wave of motion accelerates along its length until it breaks the sound barrier at the tip.
The sound speed of air is effectively the average speed that the air molecules are bouncing around at. Information is therefore transferred at the sound speed of the medium. When you’re going supersonic, the information that an object is coming towards the molecules can’t be transferred fast enough so the molecules can’t get out of the way and end up colliding with one another. This is what results in a sonic boom and shockwave.
Latest Answers