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Posts Tagged ‘Violin’

Harmonics

Because of a general lack of…imagination , we shall once more explore the mysteries of the violin!  After playing around with natural harmonics on Friday’s lab with Adeline, I decided to do a little bit of research.

By using Sound Sensor and playing the open A string, you can view the frequency spectrum.  You can see the fundamental frequency and its multiples following it(2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x…). 

 OpenA.jpg picture by xtaintedwatersx

When you play the 2nd harmonic/1st overtone on the A string (by lightly placing your finger at the middle of the string), you create a node and force that point on the string to remain stationary.  This eliminates some of the frequencies present earlier: only the even multiples (2x, 4x, 6x, 8x…) can exist. 

 2ndHarmonic.jpg picture by xtaintedwatersx

Likewise, when playing the third harmonic with a finger placed at 1/3 of the string length, only certain multiples of the fundamental frequency (3x, 6x, 9x…) are present.  And so on…

Another item of interest is how the bowing arm can influence timbre/harmonic content.  By playing closer to the fingerboard of the violin (the black strip of wood under the strings), you emphasize the fundamental frequency.  By playing closer to the bridge of the violin (the little wooden part supporting the strings), you emphasize the higher harmonic multiples.  Imagine the conductor of an orchestra saying “Bring out the fundamental frequency!” xD

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It’s finally December 1st!  Only eighteen more days till the best day ever!! ^ ^

A good example of harmonic motion that I have the joy of experiencing nearly every day is that of the violin string.  When plucked, the string oscillates up and down, exhibiting periodic motion.  A restoring force proportional to the displacement from equilibrium causes this motion. 

The tuning pegs change the tension of the string.  When turning the peg away from you, the violin string has more tension, making the restoring force greater.  This increases the frequency of the string, and since that’s proportional to wave speed (v=λf), wave speed increases too.  The more you tighten it (without breaking it), the higher the pitch. 

My Violin!!! which needs some polishing...xD

Thicker strings vibrate more slowly.  They are more massive and a greater linear density.  This means that the string has a slower wave speed and a lower frequency, making its pitch lower than that of a thinner string.  Which is why the G string has a much lower pitch than the E string.  By placing the fingers of your left hand down on the string before plucking, you can play different notes.  This is because you have shortened the length of the string that is free to vibrate and that raises the pitch of the note.

That shall be all for now…isn’t Temple Square pretty? Winter Kao Ani

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Work, Physics, & Soccer

Yay for the long weekend!  Not so yay for the increased homework load and excessive number of tests next week!

On Saturday I got pathetically lost.  No need to get into details but I still blame a certain police officer and his completely erroneous instructions.  Combined with my horrible sense of direction, it was…just bad.  Very bad.

So I basically end up circling a 500-acre park.  The only good things I got out of this two miles long detour were beautiful observations of the physics universe.  After all, it was hard to ignore the bajillions of tiny soccer players screaming and running.  And of course, the kicking of the muddy soccer ball.  (I did not have a camera at that moment, so here are substitute pictures.)

Beanie Soccer BallBeanie Soccer Ball 2Beanie Soccer Ball 3

One soccer ball had no kinetic energy, but not for long.  A youngster soon ran up to it and kicked it hard towards the goal.  The force exerted by her foot accelerated the ball.  Expressed in a simple work-kinetic theorem equation, the work done by her foot on the ball should have been equal to the change of kinetic energy of the ball.  However, to be more accurate, we’d have to account for friction between the ground and the soccer ball slowing it down too.

And did I mention that during this whole time, I was carrying my ponderous violin case with me? But since the force I was exerting (up) was perpendicular to the displacement (forward), a physicist would have concluded that I was not actually doing any work.  How sad.

Thankfully, the rest of Saturday was rather uneventful.  I did pretty much nothing except go and check out Punahou’s “canteen” for the Class of 2013.  Lots and lots of food…and no one even noticed me. : )

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