Sound travels in the same way whether it is music or noise. The difference between music and noise is that musical sounds are organized into patterns that have pitch and rhythm whereas noise is just random, disorganized sounds.

A particular musical note is determined by the number of times that the musical instrument vibrates per second resulting in a sound wave. The number of times that a sound wave vibrates in a second is called its frequency. Scientists measure the frequency of sounds in cycles per second and express the measurement in Hertz.

High note vs low note diagram
		The human ear can detect a range of frequencies. There are frequencies that are too low to detect but can be heard by other creatures, such as whales, and there are frequencies that are too high for us to hear, such as those produced by bats when trying to avoid other objects.
So we know how higher and lower notes are produced but how are louder and softer notes made?
		Put simply, louder notes are made by bigger vibrations and softer notes are made by smaller vibrations, although the number per second, or frequency, of vibrations may remain the same. The loudness of a musical note does not necessarily change its frequency.

Why do different instruments sound different? 

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