The Physics of Music Why Music Sounds the Way it Does, and Other Important Bits of Information

What is Sound?  Sound is waves.  Specifically, sound waves are consistent, recurring, oscillating sine waves.  These waves cause your inner ear to vibrate, which is then translated into sound via nerves to the brain. The brain decodes the sounds it hears into comprehendible units- speech, noise, music, etc.  Sound is waves.  Specifically, sound waves are consistent, recurring, oscillating sine waves.  These waves cause your inner ear to vibrate, which is then translated into sound via nerves to the brain. The brain decodes the sounds it hears into comprehendible units- speech, noise, music, etc.

Anatomy of a Sound Wave  Amplitude- how tall the wave is  Determines how loud the sound is  Frequency- length of wave from peak to peak  Determines pitch- the shorter the distance, the higher the pitch  Amplitude- how tall the wave is  Determines how loud the sound is  Frequency- length of wave from peak to peak  Determines pitch- the shorter the distance, the higher the pitch

Anatomy of a Sound Wave  Amplitude is commonly measured in decibels.  Frequency is measured in hertz.  1 hertz = 1 vibration per second  60 hertz = 60 vibrations per second  Amplitude is commonly measured in decibels.  Frequency is measured in hertz.  1 hertz = 1 vibration per second  60 hertz = 60 vibrations per second

 Compare these two sound waves  Wave 1 and 2 are the same pitch, but wave 2 is louder.  Compare these two sound waves  Wave 1 and 2 are the same pitch, but wave 2 is louder. Wave 1 Wave 2

 Compare these two sound waves  Wave 1 and 2 are the same dynamic level, but wave 2 is higher in pitch.  Compare these two sound waves  Wave 1 and 2 are the same dynamic level, but wave 2 is higher in pitch. Wave 1 Wave 2

Pythagoras  Greek philosopher, mathematician, musician, scientist  Developed ideas about geometry and sounds waves (music).  Greek philosopher, mathematician, musician, scientist  Developed ideas about geometry and sounds waves (music).

Pythagoras’ Idea  His idea was simple: harmonious sounds would occur by dividing a vibrating string into simple ratios.  This shorter string is exactly half as long as the longer string, a ratio of 2:1. The short string will vibrate at an interval of an octave above the longer string.  His idea was simple: harmonious sounds would occur by dividing a vibrating string into simple ratios.  This shorter string is exactly half as long as the longer string, a ratio of 2:1. The short string will vibrate at an interval of an octave above the longer string.

Pythagoras’ Idea, continued  These two strings have a ratio of 3:2. The shorter string will sound a Perfect 5th above the longer string.

Pythagoras’ Idea, continued  These two strings have a ratio of 4:3. The shorter string will sound a Perfect 4th above the longer string.

The Overtone Series  Based on Pythagoras’ discoveries, we now understand that a sound wave does more than create one frequency- it divides itself!

The Overtone Series, pt. 2  Because of the wave dividing, this creates more than one audible tone- it creates overtones.  Let’s say this great C is the pitch that we are playing. We will call this our fundamental. As soon as this fundamental plays, the sound waves begin to divide.

The Overtone Series, pt. 3  The first overtone is the simplest- 2:1, octave.

The Overtone Series, pt. 4  The next overtones invoke the 3:2 and 4:3 ratios: Perfect 5th and Perfect 4th.

The Overtone Series, pt. 5  As the ratios get more complex, so do the overtones.  The highlighted B-flat is an out of tune overtone; that is, it isn’t a perfect B-flat- you wouldn’t use it to tune your instrument!  As the ratios get more complex, so do the overtones.  The highlighted B-flat is an out of tune overtone; that is, it isn’t a perfect B-flat- you wouldn’t use it to tune your instrument!

The Overtone Series, pt. 6  These are the overtones I expect you to know! A fundamental and its first 9 overtones:  Fundamental, octave, P5, P4, M3, m3, m3 (out of tune), M2, M2, M2  These are the overtones I expect you to know! A fundamental and its first 9 overtones:  Fundamental, octave, P5, P4, M3, m3, m3 (out of tune), M2, M2, M2