Violin Sound range – (frequency response)
You might think the sound of the violin A string is 440Hz, and it is. But there are also harmonics of this because the string vibrates in multiple modes. For a plucked string you get just a few harmonics. This is what it looks like. For a cheap ‘tinny’ violin you might get a whole lot of different frequency vibrations.
Basically the string vibrates through the the bridge down to the body, and the back through the sound post. A good body filters and amplifies the pleasing vibrations.
Note the peak at 440Hz, which is then repeated at multiples of 440 up to and above 9000Hz. There are at least 10 harmonics here audible to the human ears before they start to drop away. This recoding pictured is from my 125yr old European violin, these higher frequencies are where the tone and beauty of the violins sound come from.
Bow modes of vibration
A bowed string is completely different and pulls and then slips on the string and pulls again creating aslip, drag, slip “sawtooth shape. It can also rotate the string about its axis – which i suspect creates the ‘wolf’ tones you hear sometimes. This creates a lot more higher harmonics and the real beauty oand complexity of the violins sound.
But here is the thing, the bow also vibrates…yes its ‘alive’ as well. And how those vibrations are carried or filtered out by the bow are as important to how the violin sounds as the violin itself. This is is people pay so much money for a good bow
(Image: Gough, C. E. (2012). Violin bow vibrations. The Journal of the Acoustical Society of America, 131(5), 4152-4163.)
Responsiveness
Players measure the responsiveness of the bow by giving it a step function excitation and feeling its resonance in the bow-hold hand. we can do this too with a vibration sensor. Here the frequencies of vibration are similar to the violin itself for the good bow. For a cheap bow how it filters out these vibrations..leading to a poorer tone (subjective measure). Notice how the bow rings for a time with the better bow – imparting more into the string to produce a better tone.
Stiffness of Bows comparison
The Stroop stiffness test is one method Luthiers (violin makers) use to assess a bow, its a static measure of the bows stiffness, that is how much does it bend with an applied force. Sounds complicated right? Its not really hold the bow at both ends and measure the bow height at its lowest point, hang a weight and measure the drop. Its been done this way for a long time so the weight is 10Oz and the deformation is measured in thousandths of an inch…we might go metric one day )
