WHAT's SOUND...

 Sound is...

A vibration or wave of air molecules caused by the motion of an object.The wave is a compression wave where the density of the molecules is higher.This wave travels through the air at the speed dependent on the temperature.A sound wave contains energy,which in turn means it can make things move.However,if the wave strikes something solid,the wave will bounce back--an echo.Sound energy can be changed into other forms of energy eg.electrical energy,and vice versa;this is one of its properties that allow us to communicate by telephone.

Sound vibration is....

Sound is produced when an object moves or vibrates.Without movement there will be no sound.When an object moves or vibrates ,the air molecules around the object also vibrates.Vibrating object (as long as they are not in a vaccum) produces sound. Sound travels at different rates in different media.In dry air,sound travels at 331.6 metres per seconds.Each molecule moves back and forward only a tiny distance,but it is enough to cause the air particles to bump into each other.This creates areas where there are many molecules pushed close together--compression;and areas where molecules are spread far apart--rarefactions.These compression and rarefactions move outwards away from the sound source in circles.A sound wave is created when a series of these pressure changes /waves move through the air.

Physical charcteristics...

Any simple sound,such as a musical note,may be completely describe by specifying three perceptual characteristics: pitch , loudness(or intensity) and quality(or timbre).These characteristics correspond exactly to three physical characteristics: frequency , amplitude and harmonic constitution,or waveform,respectively.Noise is a complex sound,a mixture of many different frequencies or notes not harmonically related.

Sound needed a medium...

By the means of a medium,or sound carrier,sound travels from a vibration object to your ear.A solid,a liquid or a gas can be the medium,when there are on medium to carry the sound to our ear,we cannot hear the sound.Eg. astronants at the moon cannot communicate directly to each other.They can only speak to each other by radio.This is because the moon has no air.

Speed of sound...

The speed of sound depends on the medium.For example,in the air sound travels at the speed of about 335 metres(6100 feet) a second.Sound travels about 4 times as fast in water as it does in air.Sound travels even faster in solids.In steel and in aluminum,the speed is about 15 times faster than it is in air.