2006-08-22 06:25:55 · 32 answers · asked by BINTU 1 in Science & Mathematics ➔ Physics
Not one of the answers you've seen thus far is correct.
First, sound travels better, not worse, through solids (and liquids) than it does through air. For example, passive sonar can pick up sound waves from thousands of miles away from the sonar receiver. SOSUS is a submarine detection system along the U.S. coastline that the U.S. Navy uses to pick up submarine sounds as far away as the eastern coast of Asia. Can't do that in air.
Second, impedance mismatch is why sound is attenuated when it passes from air into that wooden door you closed. Because the two media (air and wood) are different densities, they carry sound at different speeds. So when the sound from one medium tries to enter another medium, some of its energy is lost (reflected) due to the change in media; and that's what causes the attenuation. Check this out:
"Mediums in which the speed of sound is different generally have differing acoustic impedances, so that, when a sound wave strikes an interface between the two, it encounters an impedance mismatch. As a result, some of the wave reflects while some is transmitted into the second medium. " [See source.]
2006-08-22 08:31:26 · answer #1 · answered by oldprof 7 · 1⤊ 0⤋
Aaaah!
But what happens when someone down the other end of the hall shouts, "Hey BINTU! Do you want a cup of tea and a slice of gooey birthday cake with lots of ice cream followed by a large glass of fizzy white wine?" and the door's shut?
Well, I'll tell you what happens.
All those words come tearing down the hall at whatever the speed of sound is and hit the door that is shut.
They all crash into the door and fall on the floor in a big heap.
Then, thinking you just heard something, you open the door to see what it was, and you find a pile of words. You go and get a dustpan and brush, sweep them all up and then sprinkle them on the table.
Unfortunately, as you do so most of the letters get broken up and all you are left with is loads of letters.
As you've got to know what it all means, you try to put them all together again, but of course you probably put them back together completely wrong and finish up with, "God I hate you. You've got a funny nose and a silly haircut," or something like that.
Sure, you might have a few letters over - but dhkr tgsm doesn't mean a lot.
So that's why you must never shut doors!
At least not if it's someones birthday!
2006-08-22 06:42:08 · answer #2 · answered by Anonymous · 1⤊ 1⤋
Because the flat surface of the door reflects the sound waves that would normally travel straight into your room (if the door was wide open). This dampens the sound outside your door.
2006-08-28 12:12:02 · answer #3 · answered by opala m 1 · 0⤊ 0⤋
sound waves use the air as medium for travel. so, if air moves sound also moves (or say travels). if you are closing the door, you are blocking the air from entering your room. so, sound cannot enter your room.
even if you close the door, you can hear some sound because, some air is entering your room from the small openings in the door. if you can close the door completely, as done in an AC room, you cannot hear anything.
2006-08-22 06:41:30 · answer #4 · answered by Anonymous · 0⤊ 1⤋
air is a better conductor for sound waves. the more objects you have between you and whatever is making the noise, the softer it gets. also, density affects noise conductance. a great way to prove this is if you have a badass car stereo but the vibrations in your trunk make it sound like crap, take foam and fill in the gaps. it has 2 effects, first it limits the amount of sound passing through the trunk, and second you now have more material to bounce the sound back giving you better quality inside your car.
2006-08-29 22:22:01 · answer #5 · answered by Littlemman 2 · 0⤊ 0⤋
the door block out some of the sound wave
2006-08-30 00:03:20 · answer #6 · answered by curious 2 · 0⤊ 0⤋
i know sound waves travell fast through solid, that's what i learn at school, but still i close the door to reduce the sound. that's what i experience.
2006-08-22 06:36:09 · answer #7 · answered by Anonymous · 0⤊ 0⤋
To weaken the sound waves. By the time they've filtered through a solid surface they've been slowed down and the frequency has been weakened by resistance.
2006-08-22 06:33:59 · answer #8 · answered by Anonymous · 0⤊ 0⤋
Sound is carried in waves, not the wibbly wobbly waves, but the pushy waves of compression and expansion. Air is squashy so it works quite well, wood isn't.
2006-08-22 21:38:14 · answer #9 · answered by paul B 3 · 0⤊ 0⤋
sound is caused by the movement of air (compressions & rarefactions). the door prevents the air from oscillating back & forth. Thus deadening the sound.
this oscillation is the wavelength & thus determines the frequency. Freq is inverse of wavelenght/time.
2006-08-22 07:10:18 · answer #10 · answered by Anonymous · 0⤊ 1⤋