MUSIC IS VIBRATION It's a Saturday night and thousands of screaming fans are crowded into a stadium On stage a singer holds a microphone and fills the air with her energetic melody Beside her the twangs of an electric guitar boom from giant vibrating speakers The sound waves resonate all the way to the seats in the back row Listeners clap in time with the beat Hours later they will still hear the sounds of the music in their ears Music performers use technology so they can be heard by thousands of fans in concert 5 CHAPTER ONE
Sound travels through vibrations The human ear and brain hear these vibrations as sound What Is Sound Sound is a type of energy made from a vibrating source When something vibrates its particles move back and forth The particles do not move far Instead they bump into others nearby In turn those particles bump into those around them The energy gets transferred outward 6
This movement of energy is called a sound wave Unlike waves on a lake or ocean sound waves do not drift up and down Instead sound waves move back and forth like an accordion Sound waves create areas where there are many particles close together and areas where there are few particles together Not all sound waves are the same Some waves carry a lot of energy and push many particles together But just because a wave carries a lot of energy does not mean it will sound loud The person hearing the sound determines its loudness A sound may seem loud to one person and not to another A sound’s intensity is measured in 7 Silent Space Sound travels when air molecules bump into one another A vacuum is an area without air molecules Outer space is a vacuum No sound can travel there Two astronauts floating next to each other in space would not be able to hear each other even if they could speak through their thick suits Astronauts can hear one another inside spacecraft That’s because there is air inside the craft
