Why does a plane create a delayed sound after the airplane has already passed over you?

OK so phrasing the question is difficult. To explain some friends and I were at a park near an airport and we noticed the planes would pass over our heads and ten seconds later when no other plane was in sight there would be a weird new lingering noise of the plane that had just passed. Is it a lingering wake of noise from the plane that had passed?|||You may be hearing the sound of the wake vortex coming off of the wing flaps. It depends on the particular aircraft, some are more noticeable than others but trailing off of the outboard edges of the wing flaps is a wake vortex. That is where the air has built up in front of the flaps and spills over the sides of the flap on the downwind side, creating a vortex. Air is a fluid. Air is not a liquid but it IS a fluid. Sometimes in high humidity conditions you can actually see the little tornadoes coming off of the flaps. The flaps are extended to slow the plane down. They create drag. It's like opening a barn door in a stiff breeze. There is lots of surface area to get caught by the wind and it concentrates in front of that door area until it can force it's way around. These little tornadoes can last for several seconds and can be dangerous to the next plane landing. That's why you will sometimes hear the tower controller warn the next plane like this, "Caution wake turbulence of departing heavy jet." If you were close enough to the landing aircraft this might have been what you heard. The wake vortex. Pretty neat. You don't hear that every day.|||Sound travels at about 1,100 feet per second. Let's say the airplane is at 10,000 ft and is traveling at 250 mph (365 feet per second). So as the airplane travels 365 ft per second, it's noise travels 1100 ft per second. It will take 9 seconds for the sound to get to the ground where you are standing. The airplane will travel 3200 feet or a little over 1/2 mile down range before you'll hear the sound.





But since sound travels faster than the airplane (most cases), you'll hear the airplane approach you before you'll see it.|||remember light is faster than sound


sound travels roughly 720-770 miles per hour.


light travels roughly 186,282.397 miles per second in a vacuum, such as space.


So therefore when there is a plane flying above you, you see it first because light travels faster than sound then you will hear in above you because the sound waves are trying to reach you while the plane is probably already off in the distance.|||Yes....its generally because of two things.....first one is DOPPLER EFFECT.....is a phenomena, related to sound....( go to Google, and search it in wikipedia, as it is a vast subject), the second one is WAVE COMPRESSION, is happened by the speed of the aircraft.normaly sound travels around a 920 km/h, but vary according to media, atmosphere, and altitude,almost, and when a body travels through the air, it makes a compression around that body....in most of the cases, in SUBSONIC SPEEDS, that compression will be just behind the aircraft....because of the further resistance of the air mass around it.....so there must, be a wave compression, just behind the travelling body, or an aircraft....so you can only hear the roar of the aircraft, just after it....if the aircraft is travelling faster than sound, the wave compression, will be great, enough to kill you at ground, because of the intensity of the wave compression, as aircraft rips through the air mass, just like a carbide tipped drill bit drills in to a concreate media......more simply, as the speed of the aircraft is increased the sound wave with it can only reach after it, due to two effects i mentioned above......|||If a person yells at you and they 1100 feet away it will take one second for the sound to reach your ears; if they are 5 times further away at 5500 feet distance the sound would take 5 seconds to reach your ears. Sound travels at 1100 feet per second, light travels 186,000 miles per second, to the moon in 1 and a half seconds.|||sound needs a second to travel 1000 ft in air, in surface temperature.. and density





a[speed of sound] = sqrt (kappa* density*temperature [in kelvins])





so it's even smaller at high altitudes (low density,low temperature)














hence it takes time to travel from the altitude to your ears.|||Sound travels a lot more slowly than light, so you can see an airplane passing long before the sound of the airplane reaches you. As a result, the sound will tend to lag behind the airplane as you watch it, in both time and position.|||It takes time for the sound to reach you. Same as when someone shoots a gun, explodes something or hits a nail with a hammer far away from you. You will see it happen, but it takes time for the sound to get to you. Sound travels at a much slower pace than light.|||Because the speed of sound is much much slower than the speed of light. In other words, you see something before you hear it. If the something is very far away, then there will be a very noticeable delay.|||That is just the rest of the sound catching up to you. you are t a decent distance form the plane so the noise can take a little bit to get to you.|||Look up "speed of sound". Whatever it is, chances are some airplanes can fly faster than thier sound travels.





Also, you might want to look up "sonic boom" on youtube or someplace. It's pretty cool.