# Breaking the Sound Barrier

So I was outside and saw some jets fly overhead. It was quiet when they passed over then I heard the noise a few seconds later. Then I got to thinking. When breaking the sound barrier, can the jet pilot hear any sound at all? Or is it quiet? (A dumb question, but yeah.)

Sorry I shoulda specified, what about the pilot inside? does he hear anything?

Any of the sound that would have passed through outside of the aircraft would be gone. However, the air within the craft stands still relative to the pilot. Sounds that normally goes through the aircraft would still go through.

Depends on how fast he’s going, the pilot will only hear certain angles of sound created by the craft cutting through the air. He would still hear the sound of the air grazing through the tip of the aircraft though.

when you break the sound barrier. it causes a “sonic boom” like a pressurised compression blast of wind can pretty much obliterate anything. thats why no planes are allowed to hit mach 1 over a populated area.

Ok I thought I should correct some mistakes here.

The reason the sound appears as though it’s behind the plane is because light travels much faster than sound. As the plane is so far away you notice the difference in travel time between the light (where you see the plane) and the sound (where you hear the plane).

Dopler Effect is where sounds (or light ie red shift) waves are compressed or expanded due to the source or reciver moving. This is well noticed with police cars where their siren appears to change pitch as they pass.

The speed of sound is 340.29 m/s, (pretty darn fast) the rush of wind caused by a truck passing is just air caught in eddie currents at the rear of the truck. Much like what you see just behind the spoon in a cup of coffee as you stir it.

As for your question, The pilot will always hear sound, as the sound travels though the material of the aircraft, then though the air in the cockpit to his ears. However, once past the speed of sound it will become more quite as a majority of the sound produced by the jet will effectively be left behind, relative to the pilot.

heres a crap picture. the pilot doesnt hear the boom. but everyone else does

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a sonic boom will always be behind the pilot. and the speed of sound isnt that fast. think when you walk on the side of a highway, and a truck goes past you. then like 3 seconds later. theres a strong breezes. thats like a VERY small mini version of a sonic boom.

What you saw was what some refer to as the “Doppler Effect.” First you see it, then you hear it. They were ahead of the sound barrier but unless you hear a big boom followed by rattling or shattering windows and car alarms going off, they hadn’t passed the sound barrier yet.

If you just heard a rumbling then that’s just the collision of cold air meeting hot air (at least, that’s what I was told in aviation maintenance school).

Any other aviation related questions I’d love to answer them! 8D

I don’t think the jet pilot would hear anything, but when the jet breaks the sound barrier, it creates a sonic boom.

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