The Physics of Playing a Guitar Visualized: Metallica’s “Nothing Else Matters” Viewed from Inside the Guitar

Give it a chance, you won’t be dis­ap­point­ed. While the first 30 sec­onds of the video above may resem­ble an ama­teur iPhone prank, it soon becomes some­thing unex­pect­ed­ly enchanting—a visu­al­iza­tion of the physics of music in real-time. The Youtu­ber places his phone inside an acoustic gui­tar, then plays Metallica’s “Noth­ing Else Mat­ters” against a back­drop of clouds and blue sky. Due to what Twist­ed Sifter iden­ti­fies as the phone camera’s rolling shut­ter effect, the actu­al waves of the vibrat­ing gui­tar strings are as clear­ly vis­i­ble as if they were on an oscil­lo­scope.

The com­par­i­son is an apt one, since we might use exact­ly such a device to mea­sure and visu­al­ize the acoustic prop­er­ties of stringed instru­ments. “A gui­tar string”—writes physi­cist and musi­cian Sam Hokin in his short explanation—is a com­mon exam­ple of a string fixed at both ends which is elas­tic and can vibrate.

The vibra­tions of such a string are called stand­ing waves, and they sat­is­fy the rela­tion­ship between wave­length and fre­quen­cy that comes from the def­i­n­i­tion of waves.”

Those with a physics back­ground might appre­ci­ate The Physics Class­room’s tech­ni­cal descrip­tion of gui­tar string vibra­tion, with sev­er­al tech­ni­cal dia­grams. For oth­ers, the video above by Youtube physics teacher Doc Shus­ter may be a bet­ter for­mat. Shus­ter explains such enti­ties as nodes and antin­odes (you’ll have to tell me if you get any of his jokes). And at about 2:25, he digress­es from his mus­ings on these phe­nom­e­na to talk about gui­tar strings specif­i­cal­ly, which “make one note for a giv­en tight­ness of the string, a giv­en weight of the string, and a giv­en length of the string.”

This is, of course, why chang­ing the length of the string by press­ing down on it changes the note the string pro­duces, and it applies to all stringed instru­ments and the piano. Oth­er fac­tors, says Shus­ter, like the body of the gui­tar, use of pick­ups, etc., have a much small­er effect on the fre­quen­cy of a gui­tar string than tight­ness, weight, and length. We see how the com­plex­i­ty of dif­fer­ent stand­ing wave forms relates to har­mon­ics (or over­tones). And when we return to the Metal­li­ca video at the top, we’ll have a bet­ter under­stand­ing of how the strings vibrate dif­fer­ent­ly as they pro­duce dif­fer­ent fre­quen­cies at dif­fer­ent har­mon­ics.

Shuster’s video quick­ly laps­es into cal­cu­lus, and you may or may not be lost by his expla­na­tions. The Physics Class­room has some excel­lent, free tuto­ri­als on var­i­ous types of waves, pitch fre­quen­cy, vibra­tion, and res­o­nance. Per­haps all we need to keep in mind to under­stand the very basics of the sci­ence is this, from their intro­duc­tion: “As a gui­tar string vibrates, it sets sur­round­ing air mol­e­cules into vibra­tional motion. The fre­quen­cy at which these air mol­e­cules vibrate is equal to the fre­quen­cy of vibra­tion of the gui­tar string.” The action of the string pro­duces an equal and oppo­site reac­tion in the air, which then cre­ates “a pres­sure wave which trav­els out­ward from its source.” The pres­sure waves strike our eardrums, our brains inter­pret sound, and there you have it.

via Twist­ed Sifter

Relat­ed Con­tent:

Free Online Physics Cours­es

Oxford Sci­en­tist Explains the Physics of Play­ing Elec­tric Gui­tar Solos

The Secret Link Between Jazz and Physics: How Ein­stein & Coltrane Shared Impro­vi­sa­tion and Intu­ition in Com­mon

The Math Behind Beethoven’s Music

Josh Jones is a writer and musi­cian based in Durham, NC. Fol­low him at @jdmagness

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Comments (6)
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  • Mike says:

    Spoil­er: The string itself only vibrates back and forth in a sim­ple sine wave; it is the fram­er­ate of the cam­era that caus­es the illu­sion of com­plex waves.

  • Glenno says:

    Just to add to Mikes com­ment it’s actu­al­ly how the sen­sor scans, a rolling sen­sor scan like the iPhone will pro­duce this. Like the videos of heli­copter or drone blades that bend and dis­tort. A glob­al scan sen­sor would show gui­tar strings that are blurred in the direc­tion of the vibra­tion. Frame rates and shut­ter speeds on a cam­era would pro­duce a dif­fer­ent look that I’m not going into here.

  • Nuwan says:

    The best expla­na­tion of har­mon­ics I’ve seen is from a video by the awe­some MIT physcis pro­fes­sor Wal­ter Lewin.

    This is a pub­lic lec­ture, suit­able for both kids and adults, so he skips the tech­ni­cal­i­ties and cal­cu­lus. He does a great job of explanin­ing it with the help of some child musi­cians.

  • Christopher says:

    Would it have killed him to tune first?

  • Jessie says:

    I total­ly agree. It’s also not just about learn­ing how to play the gui­tar that gui­tar instruc­tion is all about. If you’re just start­ing out as a gui­tarist, it’s a good idea to brush up on a lit­tle bit of gen­er­al his­to­ry, and this guide will teach you every­thing you need to get start­ed.

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