instrument resonance

Edited: July 15, 2019, 5:08 AM · Singing into my violin reveals that it resonates at about middle C or C#, yet these aren't wolf notes, which is fortunate. Err, and possibly also inexplicable!

Replies (9)

July 15, 2019, 5:56 AM · That's the resonant frequency of the cavity resonance, usually pretty similar on most violins
July 15, 2019, 6:42 AM · The cavity resonance depends on the internal dimensions of the violin, which can, and does, vary. For example, my Jay Haide, a fairly standard 14" violin, has a clear internal resonance of D, whereas my old violin, a 14-1.4" with bout and rib dimensions pro rata, has a resonance of C.

Violas, so I understand, can also have an internal resonance of C, which leads me to the conclusion that my 14-1/4" violin wanted to grow up and become a viola, but never quite made it.

July 15, 2019, 8:29 AM · Cavity resonance is explicable. The lack of wolf notes is what puzzles me.
July 15, 2019, 8:59 AM · I thought that the air resonance would enhance the sound, rather than create wolf notes... the "wolf note" is created by partial damping, surely?

However, my violin does have a tendency to wolf a bit around middle C and the octave above it, and it's a relatively large instrument, so it might well be connected.

July 15, 2019, 11:17 AM · The "Helmholz Resonance" of string instruments is related to the flow resistance due to the f-hole area and the top-plate thickness at the f-hole edges. This can be critical to viola sound. Some viola's cavity resonant pitch can be lowered by effectively making the top plate thicker at the f-hole edges. A strip of tape about 3/4" wide around most of the two f-holes* can make a big difference on some violas. I did this with one of my violas for 20 years until I found just the right string combination.

*perpendicular to the plane of the top.

https://lisafea.com/pdf/JMC-Helmholtz_Resonance--Re-ct2.pdf

Edited: July 15, 2019, 3:52 PM · The air (cavity) resonance is strongest at one note, but is fairly spread across several, especially if the f-holes are large.

The most common wolf tone is centered on one strong note, either side of the open A, vibrating strongly in the lower left zone of the top plate; but if it is as high as C/C#, it may conflict with the octave of the air resonance, causing instability.

Edited: July 15, 2019, 4:56 PM · For many years I've been aware of an interesting resonance on my old violin (that's the 14-1/4" one), and it's apparently not related to the cavity resonance. No matter how strongly I play the 880Hz A on the E string it still does not sound quite as powerful as it should when compared with the G and B either side of it, played equally strongly.
I
've realised what is happening. This particular old violin is very resonant, and when the 880Hz A on the E string is played (in tune!) it excites the A harmonics, also at 880Hz on the open A and D strings. The A I'm playing on the E string is evidently losing some of its energy to those harmonics on the A and D strings. The answer is simple: if I want a strong tone out of the E-string A then I lightly touch the A and D strings with my index finger just above the nut, and the E-string A now sings out as it should.

That E-string A also sings out if the A and D strings aren't quite in tune and so not producing the 880Hz harmonic - I tried the experiment.

I don't get this effect with the E-string A on my Jay Haide, but then it is not a violin quite in the same class as my old one.

The string set currently on my old violin is Warchal Amber, which are very stable under most conditions, but I've long been aware of the E-string A losing a little of its power no matter what strings I've used. Now I know why.

Andrew Victor mentioned in another post recently that he places a little square of chamois between the E-string and the nut to alleviate the metallic sound of the open E. I've tried it and it works like a charm. The open Amber E now sounds as smooth as the fingered F or F#. Thank you, Andrew, for that tip! I've also rubbed some black pencil lead onto the chamois so that its dazzling presence is now no longer noticeable ;)

July 15, 2019, 4:53 PM · Does one typically mute the strings when measuring the cavity resonances?
Edited: July 16, 2019, 6:19 AM · @Adrian "The most common wolf tone is centered on one strong note, either side of the open A". Yes, I've noticed for a while that I have to be careful when playing Bb or B. I'll check out the G more closely in a minute.

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