An helicopter just went past on top of my house 5 mins ago. while I was in my room, the floor and my laptop started to vibrate as it was passing by.
2007-01-31 07:29:06 · 12 answers · asked by I'M GONNA GO PLACES 5 in Cars & Transportation ➔ Aircraft
Because the rotors are vibrating a small bit while slicing through the air.
2007-01-31 07:32:29 · answer #1 · answered by Kenster102.5 6 · 0⤊ 1⤋
Don't know about the noise, but lowflyer is incorrect on his blade tip info. From wikipedia:
When the helicopter is at rest, the outer tips of the rotor travel at a speed determined by the length of the blade and the RPM. In a moving helicopter, however, the speed of the blades relative to the air depends on the speed of the helicopter as well as on their rotational velocity. The airspeed of the forward-going rotor blade is much higher than that of the helicopter itself. It is possible for this blade to exceed the speed of sound, and thus produce vastly increased drag and vibration.
2007-01-31 17:31:58 · answer #2 · answered by Anonymous · 0⤊ 0⤋
The THUMP THUMP that rattles your house is Low Freq vibrations Caused by the interaction of the Tail Rotor turbulance with the Main Rotor Turbulance.
The LENGTH of the blades have little or noting to do with noise.It the CHORD WIDTH and NUMBER of blades.By increasing the Chord Width of the Main Blades, how thick and wide it is, as well as increasing the number of blades., You somewhat cut down on the noise. A good example of this is the Russian Hind and the MH-53J, both make more of a "whirling noise" then a thump. Both A/C have VERY LONG BLADES.Even with all these modifacations you still have at least 2 turbines screaming which in itself is enough to rattle your house.
2007-01-31 17:59:42 · answer #3 · answered by Wolf of the Black Moon 4 · 0⤊ 0⤋
When a helicopter is flying towards your location you will hear pop, pop, pop, sounds. As the rotor of the helicopter goes round and round the end of the rotors are moving faster through the air than the middle or the part where it's attached to the rotor mast. The tips of the rotors are going supersonic and the popping sounds you are hearing can be best described as miniature sonic booms.
2007-01-31 14:58:53 · answer #4 · answered by ericbryce2 7 · 0⤊ 0⤋
Wow
What a load of misinformation.
The tips of the blades are not going sonic. As they approach the speed of sound, the compressibility factor causes a loss of efficiency, so the rotor speed is limited to about 450 mph at the tip.
What you are likely feeling is the compression of the air by the blades, or more likely the shock wave produced by the sound wave. It is likely the machine that flew over had a two-bladed rotor system, which tend to have a longer blade and thicker chord, thus creating sound at a lower frequency, which you will "feel" as more impacting.
It is true that we move a lot of air while flying. The bigger the machine, the more air that will be disturbed, thus the larger footprint on the ground below. Plus we tend to fly lower than most airplanes (perfectly legal, by the way), so will tend to appear louder.
2007-01-31 08:00:28 · answer #5 · answered by lowflyer1 5 · 6⤊ 0⤋
Sigh - so many wrong answers.........
Here's a basic physics lesson. All "noises" are just simply pressure waves caused by something disturbing the air around us. These waves can be of any frequency / amplitude, and they are picked up by our ears and interpreted by our brain as a recognisable sound.
The helicopter passing over your house will be disturbing the air around it as it moves past, and causing pressure waves to eminate from it. The properties of these waves are such that it interacts with your house - as their amplitude will be high enough to make the room vibrate.
Your ears are picking up these pressure disturbances and sending the information to your brain - which tells you that it recognises the waves as those made by a passing helicopter!
Lesson over!
2007-02-01 00:51:08 · answer #6 · answered by Woody 3 · 0⤊ 0⤋
helicopter blades move alot of air at fast speeds. the sound waves from the blades "chopping" through the air, and the turbine engine would vibrate your house. most choppers have turbine engines too. its like a loud car stereo system. ever hear them come by? it kinda causes everything to vibrate. its sound waves hitting resistance like walls and air.
2007-01-31 12:29:30 · answer #7 · answered by cparkmi331 3 · 0⤊ 0⤋
They're moving a lot of air, and at any one section of the rotation of the blades, that motion is not constant. (Meaning, at one moment the blade will be hurling air at you, the next it won't then it will then it won't) Since it's got to do this a whole goddamn lot to keep in the air, if it's close to you, you're going to feel each and every one of those pulses. The shape and construction of your house probably have something to do with how much you feel it, as well.
Maybe it would help if you put something soft under your table legs to dampen the vibration?
2007-01-31 07:33:31 · answer #8 · answered by Anonymous · 1⤊ 2⤋
A bottle, like a flute, is an edge-effect instrument. The air vibrates at the hole.
2016-05-23 23:28:23 · answer #9 · answered by Anonymous · 0⤊ 0⤋
Bad answers
The reason that helicopters are so noisy is that out at the edge of the blade it is moving so fast that it is exceeding the speed of sound (you are hearing tiny little sonic booms)
2007-01-31 07:35:18 · answer #10 · answered by startrektosnewenterpriselovethem 6 · 2⤊ 3⤋