# Weird how two objects can makes sound

1. May 15, 2008

### spri4

One question ive been focusing on lately is sound. Can any of you help me understand how it is created or why we even hear it. It just seems a little weird how two objects can makes sound, or even one in some cases. Are the particles or what? I dont know.

2. May 16, 2008

### thenumber66

Sound is caused by vibration, any kind of vibration really. This vibration is produces in a number of different frequencies. We as humans can only hear a certain range of frequencies.. i believe from 20Hz to 20 KHz. If you want to hear how the vibration works just rub to rough pieces of paper or other material, first rub them slowly, then rapidly. You should hear the difference in pitch if only slightly. Hope this helps.

--66

3. May 16, 2008

### Nick89

What we percieve as sound is basically a small vibration in the air.

A sound speaker is simply a cone (a normal plate of cardboard could also work) that vibrates. When vibrating, it pushes the air molecules away from it in pulses. The air near the speaker will therefore start vibrating in the same manner. This will in turn push away other air molecules, and you get a soundwave.

A soundwave is almost exactly the same as a wave in a stretch of water, except that the displacement of the water is perpendicular to the direction of travel, while the displacement of the air in a soundwave is in the same direction as the direction of travel.

So sound is nothing more than some vibrating medium (usually a gas, sometimes a solid or liquid). If there is no medium (a vaccuum for example) there is NO sound.

You can then define things as soundpressure (the pressure exerted by the moving air molecules), sound pressure level (a logaritmic decibel scale you probably know) etc...

Look on wikipedia for more basic information about frequency, etc...