My Attempt at Defining SOUND

Sound is a rather elusive concept to define.  You can’t see it, you can’t touch it, but you can hear it...It’s unique in that it appeals to one sense only.  Most other things encountered in everyday human life trigger more than one of the five sense.  For example, you can see, smell and taste your food.  You can see and feel the sun’s rays.  But sound is different – you can ONLY hear it.

Sound is an invisible, intangible series of compression waves, like ripples on water, that are caused by vibrations.  These vibrations are the result of some disturbance, whether it be from a collision of two objects or the movement of air pushed over vocal chords, and is the source of all sound.  Sound must travel through a medium or “carrier” such as air (a gas), wood, metal, or water (a liquid) because it needs something to interact against to create the sound waves that we hear.  Vibrating objects push against the medium, creating compressed air zones.  The compressed air zone knocks into the air surrounding it, which knocks into the air surrounding it, and so on forming rippling sound waves.   

        For this reason, there can be no sound in a vacuum, such as on the Moon, because there is nothing in space for sound particles to collide with.  The speed of the sound is directly related to the substance that it travels through.