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Knowledge_Seeker
2006-Mar-12, 09:18 PM
Where does sound come from?

should'nt the engergy created by an object be distributed to another object? (isnt this one of newton's laws?)

For example. When i stomp on my apartment floor, should that engery be converted an distributed to the supports and then to the ground of the building instead of becomming loud noises for the neighbors below me? :)

antoniseb
2006-Mar-12, 09:27 PM
When i stomp on my apartment floor, should that engery be converted an distributed to the supports and then to the ground of the building instead of becomming loud noises for the neighbors below me?

No, don't stomp your feet. I'm assuming that you're fairly young, and I applaud that you are trying to understand the world around you. Sound comes from vibrations of material or sudden expansions of gasses. In the specific case of the foot stomping on the floor, lets imagine that you have a wooden floor, made of two layers of floorboards on top of some 2x10 beams spaced 16 inches apart. These beams are supported at their ends by some kind of bearing wall.

When you stopmp your foot, you bend part of the floor, and that vibration travels through the boards and through the beams, and to the bearing wall. But, this vibration is not 100% efficient. It flexes all the places in the wood where the little parts of the wood adhere to each other, and reflects of dense parts of the wood (knots), and has many other very complicated interactions, the net result of which is that sound waves are produced AND heat is given off.

Dragon Star
2006-Mar-12, 09:38 PM
What about the pressure of air? That makes sound too, such as putting your hands together and clapping.

papageno
2006-Mar-12, 09:49 PM
What about the pressure of air? That makes sound too, such as putting your hands together and clapping. Sound waves in air are pressure waves.
When you clap your hands, you disturb the air and this disturbance causes oscillations of the pressure around your hands.
(It is like throwing a stone into water: you get a wave).

Ken G
2006-Mar-12, 10:02 PM
It's really the same thing as the energy that is communicated through the boards, it's just that some of it is communicated through the air as well. After all, air has pressure, so it, like papageno's water waves, has the ability to communicate a stress. Indeed, the floorboards themselves carry sound in addition to their flexing effects (and when someone stomps on your ceiling, you hear sound that was first carried in the ceiling itself, via internal vibrations in the ceiling that get communicated to the air in your room).