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Name: Melanie
Status: student
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
Dear Scientist My daughter is a beginner on the violin. When she plays the highest E string with the bow on the open string, we can often hear a harmonic, E the octave below. This upsets her playing and 2 violin teachers have no explanation as to how to stop this. ( I play musical instruments and studied Physics to Advanced Level)



Replies:
I approach this with great humility. I am neither a string musician, nor an acoustic physicist. But from what you describe, I would try bowing the open E string at various positions along the string, maybe with different tensions on the bow. You are exciting modes that are 1/2 the frequency (double the wavelength) of the intended tone, so try to minimize the resonance of the pitch, by not making the two tones multiples of one another. I assume your daughter is not playing a "Strad". It is possible that the physical design of the instrument favors the open E string wavelength.

You live in the center of orchestral music. If all else fails call the London Philharmonic and ask to speak to a violinist. All that can happen is no one will talk to you, but my gut feeling is that you will find someone who has had a similar problem and will be delighted to contribute a bit of technique. Play some Vivaldi form me!!

Vince Calder


Melanie

Simply stated, the answer is sympathetic vibrations in adjacent violin strings and other parts of the violin.

Sound is pressure waves in the air, like when you throw a stone in a lake and see the water waves move outward, sound is the same thing, but only waves in the air.

Sound from a violin is made by vibrating the string by rubbing it with the bow. The pitch of the sound is determined by the frequency (and wavelength) of the vibration of the violin string (and the other vibrating parts of the violin). Low pitched sounds have relatively lower frequencies, longer wavelengths, Higher pitched sounds have relatively higher frequencies, shorter wavelengths.

Please see this URL for discussion of wavelength and frequency

http://www.sengpielaudio.com/calculator-wavelength.htm

please see this URL for discussion of the frequency and wavelength of musical notes

http://www.phy.mtu.edu/~suits/notefreqs.html

The pitch of the sound produced on a violin (or guitar or other stringed instrument) string depends on the length of the string. Musicians vary the sound pitch made by a string by varying the vibrating part of the string by pressing down on the string at a given length with the fingers.

Resonance occurs when the vibrations on a string (or electrical antenna) are at a frequency that the vibrations build on each other instead of cancelling out. An antenna of a certain length will receive or radiate only certain frequencies that "resonate" on the physical length of the antenna (or violin string).

Here is a precise definition of resonance:

http://en.wikipedia.org/wiki/Resonance

This article has a video in it (down near the bottom of the article) of how a structural vibration destroyed a bridge.

http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

My best description of a resonance is a child on a swing. When the swing is at its highest point (and slowest speed) and you push on it, the swing will swing higher because the push at the top re-enforces the frequency of the energy in the swing. If you push on the swing when it is at its lowest point and rising, you will insert a mitigating force on the swing and the swing will swing at a lower point.

When a given string length is vibrated with the bow, the string vibrates at its resonant Wavelength (frequency). Frequencies that are related to the physical length of the string re-enforce their vibrations, frequencies that are not related to the physical length of the string are "filtered" out.

Note that the E4 note is a vibration at a frequency of 329.63 Hz which has a wavelength of 105 centimeters.

So, when you bow a violin string, resonant vibrations build on the string and the sound is made. But it also works the other way around. Apply a sound to a violin string, and if the sound is resonant to the string, the violin string will start vibrating as well. So what you are also hearing when you bow the E string are the sympathetic vibrations of all the other strings and violin parts that resonate at that frequency (or multiples of that frequency known as harmonics) of the E note.

Sincere regards,

Mike Stewart



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