Why Violins Have F-Holes
openculture.com
openculture.com
The holes in acoustic string instruments are not there to "allow sound to escape". Sound radiates in all directions from the surface of the instrument, although the frequency balance may change from point to point. Consider drums, for example. A drum may be completely sealed, yet still work and still make sound.
The purpose of soundholes is tuning the resonant frequency of the acoustic chamber. Google Helmholtz resonators for the theory and math if you like. The area and depth of the port alters the resonant frequency, which is largely a function of volume.
Acoustic guitars usually have large, circular holes. When recording acoustic guitars, you should never point the microphone at the soundhole! You'll get a dull, woofy, severely unbalanced sound. There are many mic techniques to deal with the frequency issues, but the most common is a microphone along the neck, aimed backward at the neck/body joint. That wouldn't work if the sound just escaped from the soundhole, as the article implies.
If I put my hand near the f-holes on my cello while I play, I can feel a shocking amount of airflow in and out of the body.
The sound emitted by the holes is indeed unbalanced because that's dominated by the resonant frequency of the instrument, but that's a large part of what gives the instrument such acoustic power.
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Additionally, it does make sense that the sound is more efficiently emitted by narrow holes with lots of edge area: it's like the skin effect in electrical conductors at high frequencies, where most of the current flows near the surface of wires, rather than in the bulk.
I think the F shape has a lot more to do with limiting mechanical stress points for cracking. A round hole with the same area as the f-holes would weaken the top and create changes in how the soundboard vibrates. It's different on a flat-top acoustic guitar, where bracing rather than carving governs the strength of the top, and bracing also limits the valid locations for soundholes.
Beyond that we operate on a logarithmic scale when it comes to sound, what sounds slightly louder to us can be heard over much larger areas.
Admittedly, guitars are different from violins here, but... with a guitar, there's a pretty fixed amount of energy transmitted when a string is plucked. This energy may radiate quickly or slowly. In other words, there's a tradeoff of attack and sustain. An exaggerated case it the banjo. A banjo is loud, but has little sustain. An unplugged Les Paul electric makes little acoustic sound, but sustains for many seconds. Within the narrower world of acoustic guitars, small-bodied guitars tend to be apparently louder, but not as rich as large-bodied guitars, due to this attack/sustain tradeoff.
80 decibels, ~= 0.001 watts of energy. https://en.wikipedia.org/wiki/Sound_energy_density_level
PS: And yes most home speakers ~1% efficient. https://en.wikipedia.org/wiki/Loudspeaker#Efficiency_vs._sen... At scale they can get into the 20% range, but even that suggests guitars are probably not that efficient overall.
My cello is particularly resonant, and in hindsight (is this confirmation bias talking?) has very little sustain on pizzicato (plucking) compared to my cheap, less-resonant student cello.
On the other hand, with a guitar, the more efficient a radiator it is, the louder it is but the less it sustains, because each pluck imparts a fixed amount of energy to the instrument.
Also, my violin teacher had a couple of superb (and very expensive) old violin. And there was a lot of variation in the shape of the f from instrument to instrument. Different f-holes give different "character" to the sound but the impact on the power was really limited.
That's why violin mutes, which allow a violinist to practice quietly, attach to the bridge...to reduce the transfer of vibration to the chamber via the sound post and bass bar...
F-holes are simply one element of the whole violin, a part that contributes to an elegantly refined proportionality...
although I am not sure about the rest of your comment, this is not true, for the most part. Most drums will have some hole in them (usually either somewhere on the side or the entir bottom) to let air go in and aout of it as the drum heads resonate. of course they would still make sound with out these holes, it changes the sound quite drastically :)
Still, it gets across the idea that sound doesn't come out of the hole, but rather radiates from the entire instrument.
(This is elaboration on the point, not disagreement.)
I realize that this is how people conventionally think about it, and on the surface it's only subtly different from the real explanation, but the result is that it makes you think about the evolutionary process in a fundamentally incorrect way.
I think this is a big part of why people fail to understand how emergent systems pop up all over the place. It leads to the mistaken idea that, for example, being able to design a new economy is just an engineering problem, and we can just paste together what seems to work with our own bright ideas, and get something functional out the other end.
[1] Freaks and Geeks
So evolution is an optimization process. On a constantly changing landscape.
And this is getting away from the central point, but there's also much debate (at least at the level I'm reading; maybe it's solved by now for those in the field) about how traits can support a community at the expense of the individual - like with old humans losing the ability to procreate.
https://en.wikipedia.org/wiki/Kin_selection
tl;dr: those in the community have almost the same genes as you, so helping them is almost as beneficial as helping yourself.
The only thing evolution does is favor one adaptation over another. At that point in time, a particular mutation/adaptation may work out better (though frequently due to pure chance), so it survives and gains inertia. Inertia is a very powerful thing; it's why we have a lot of big companies that don't seem to do that well, laws that don't make much sense, etc. Once something is in place, it's hard to change it. The same thing is true of evolution. It does not always result in the most optimal configuration, or even frequently.
There's plenty of examples of things in the human anatomy which are actually terrible "design" choices, but when viewed through the lens of evolution, make sense. A famous example is some nerve (I forget the name now) that takes a ridiculous and non-sensical route, but when you look at the history of how we evolved, it makes sense that it got stuck there because of what came before. It's like that with a lot of human technology too; train tracks, for instance, weren't spaced at their current spacing (gauge) because it was the optimal design choice (esp. not now with modern trains and cargo sizes), they did it because technologies and tooling and infrastructure that came before made it easier to use that gauge than to switch to something different. If we could change things, it'd make more sense to increase the standard gauge on most railways, but there's too much inertia and it'd cost too much.
Folks on HN might like to check out the work of Joseph Curtin, a MacArthur grant recipient from my hometown. He publishes acoustic research and makes world-class instruments (i.e. mid-to-high five-digit prices). http://josephcurtinstudios.com/
It's interesting that pre-electronic instrument design was pretty much all about increasing loudness.
Instruments with a sweet tone quality, but lacking in volume, are a tough sell, and will often be modified to bring out more sound. With the exception of a few museum pieces, the Strads have all been modified over the years to make them louder, with longer necks and shorter ribs.
I suspect the cello edged out the viola da gamba because of volume.
https://www.youtube.com/watch?v=I8MUgwiZULw
It uses re-purposed printer carriage with stepper motor to generate electricity. With very low latency, the pulse of power boots a synthesizer and powers the audio amp.
> increasing loudness.
Intriguingly, it hasn't been a continuous upgrade, like computers, etc. There was at least one major stratum in this evolution when patronage for music shifted from the church to the court. With larger audiences required to financially support the music, instruments went through a major shift of amplification to use more metal parts, etc.
I also like your idea of continuing to optimize the designs. Some people are also trying different materials like carbon fiber! One issue with the simulations is that people don't comprehend the structure of wood perfectly. It's only recently that researchers have realized the importance to the sound of the wood being a non-continuous material and actually comprised of long, irregularly-shaped grains. Most of the papers I've seen are analyzing instruments and trying to figure out what the salient features are of the design.
One more caveat is that it still has to be easily buildable. The current design is excruciatingly difficult and slow.
So one thing this illuminates for me is how much instrument design is like biology :)
No major piece of a violin serves just one purpose, and all of the pieces interact. What a glorious mess.
Precisely...
I found that a very helpful when understanding the design of these instruments.
When Gibson made a signature model he asked to remove the f-holes to reduce feedback:
> The most noticeable differences between the Lucille and the Gibson ES-355TD-SV on which it is based are the "Lucille" script on the headstock, the maple neck, and the lack of F-holes on the top. King requested that, to reduce feedback, there be no F-holes.
https://en.wikipedia.org/wiki/Lucille_%28guitar%29
There's a very good song by him talking about Lucille:
One of the big reasons for the different style of top is that a bowed violin string produces much stronger vibrations than a plucked guitar string, so the body of a guitar must amplify the sound much more than the body of a violin.
One possible problem here is that the appreciation for classical music is not exactly on the rise and really high quality violins have limited applicability elsewhere. It's a matter of time before there will be more quality violins than violinists (and most of them will live in China where there is a fairly large continent of classical performers, and their numbers are actually on the rise).
I'm fun at parties.