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This article is fundamentally wrong. The holes in acoustic string instruments are not there to "allow sound to escape". Sound radiates in all directions from t

by beat 11y ago

This article is fundamentally wrong. 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.

CarVac 11y ago
I don't think it's entirely wrong, at least for violin-family instruments. 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. ... 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.
- beat 11y ago
  The air is flowing because it's a tuned resonator, not because it's making sound. That's how the tuning port works. Sound does come out of the hole, but only incidentally. Its value is tuning the chamber, not releasing the sound. The sound would be radiated regardless, conservation of energy and all that. 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.
  - Retric 11y ago
    Energy is conserved, but you may end up with heat instead of sound. Also, sound near an object behaves differently. As you stand further back you get constructive and destructive interference between different parts. 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.
    - beat 11y ago
      My unscientific opinion as a guitarist is that thermal loss isn't a dominant factor. Most of the energy put into the instrument is converted to sound. 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.
      - Retric 11y ago
        Sound contains far less energy than you might expect. 80 decibels, ~= 0.001 watts of energy. https://en.wikipedia.org/wiki/Sound_energy_density_level 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._sensitivity 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.
        beat 11y ago
        From experience, an acoustic guitar is about as powerful volume-wise as 1/2 to 1 watt electric guitar amp with a moderately efficient speaker. And there just isn't a whole lot of energy transmitted from a guitar pick to a string. Whatever the efficiency is, there aren't wide variations in acoustic guitar volume that can't be explained by the attack/sustain tradeoff.
- LukaAl 11y ago
  When I was learning violin, I used to mess around with my violin to understand how it worked (it was a very cheap one). One of the things I noticed was the covering the holes with paper changed a lot the tone of the instrument but very little the power of it. 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.
  - Outdoorsman 11y ago
    One of the things I noticed was the covering the holes with paper changed a lot the tone of that instrument but very little the power of it. 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...
Outdoorsman 11y ago
Agreed...the top and back plates of a violin radiate the majority of the sound...air circulating within the violin contributes much less... F-holes are simply one element of the whole violin, a part that contributes to an elegantly refined proportionality...
- Outdoorsman 11y ago
  If you'd like to experience (hear) the subtle variations between two violins that are, proportionally, almost identical--that is, they're "tuned resonators", listen to this exchange between Ali Bain and Nicola Benedetti, two very talented violinists, discussing their instruments... https://www.youtube.com/watch?v=zgDNSDadqos https://www.youtube.com/watch?v=zgDNSDadqos
TheSoftwareGuy 11y ago
> A drum may be completely sealed, yet still work and still make sound 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 :)
- deleted 11y ago
  [deleted]
- beat 11y ago
  Yep - I was exaggerating to make a point a bit. Although there are folk drums that are totally sealed (African talking drums, for example), the drum kit toms and snare that most people think of as "drums" are vented. It's not really the same as a tuned resonator like a violin, though. The vent is just there to ease pressure and keep the heads from choking on the attack. Still, it gets across the idea that sound doesn't come out of the hole, but rather radiates from the entire instrument.
elihu 11y ago
I don't think that's quite right. Half of the vibrating surface area of a hollow stringed instrument is on the outside, and half is on the inside. If you close up the soundhole, you'll lose quite a bit of volume just for that reason.

by beat 11y ago

CarVac 11y ago

I don't think it's entirely wrong, at least for violin-family instruments. 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. ... 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.

beat 11y ago
The air is flowing because it's a tuned resonator, not because it's making sound. That's how the tuning port works. Sound does come out of the hole, but only incidentally. Its value is tuning the chamber, not releasing the sound. The sound would be radiated regardless, conservation of energy and all that. 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.
- Retric 11y ago
  Energy is conserved, but you may end up with heat instead of sound. Also, sound near an object behaves differently. As you stand further back you get constructive and destructive interference between different parts. 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.
  - beat 11y ago
    My unscientific opinion as a guitarist is that thermal loss isn't a dominant factor. Most of the energy put into the instrument is converted to sound. 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.
    - Retric 11y ago
      Sound contains far less energy than you might expect. 80 decibels, ~= 0.001 watts of energy. https://en.wikipedia.org/wiki/Sound_energy_density_level 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._sensitivity 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.
      - beat 11y ago
        From experience, an acoustic guitar is about as powerful volume-wise as 1/2 to 1 watt electric guitar amp with a moderately efficient speaker. And there just isn't a whole lot of energy transmitted from a guitar pick to a string. Whatever the efficiency is, there aren't wide variations in acoustic guitar volume that can't be explained by the attack/sustain tradeoff.
LukaAl 11y ago
When I was learning violin, I used to mess around with my violin to understand how it worked (it was a very cheap one). One of the things I noticed was the covering the holes with paper changed a lot the tone of the instrument but very little the power of it. 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.
- Outdoorsman 11y ago
  One of the things I noticed was the covering the holes with paper changed a lot the tone of that instrument but very little the power of it. 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...

Outdoorsman 11y ago

Agreed...the top and back plates of a violin radiate the majority of the sound...air circulating within the violin contributes much less... F-holes are simply one element of the whole violin, a part that contributes to an elegantly refined proportionality...

Outdoorsman 11y ago
If you'd like to experience (hear) the subtle variations between two violins that are, proportionally, almost identical--that is, they're "tuned resonators", listen to this exchange between Ali Bain and Nicola Benedetti, two very talented violinists, discussing their instruments... https://www.youtube.com/watch?v=zgDNSDadqos https://www.youtube.com/watch?v=zgDNSDadqos

TheSoftwareGuy 11y ago

> A drum may be completely sealed, yet still work and still make sound 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 :)

deleted 11y ago
[deleted]
beat 11y ago
Yep - I was exaggerating to make a point a bit. Although there are folk drums that are totally sealed (African talking drums, for example), the drum kit toms and snare that most people think of as "drums" are vented. It's not really the same as a tuned resonator like a violin, though. The vent is just there to ease pressure and keep the heads from choking on the attack. Still, it gets across the idea that sound doesn't come out of the hole, but rather radiates from the entire instrument.

elihu 11y ago

I don't think that's quite right. Half of the vibrating surface area of a hollow stringed instrument is on the outside, and half is on the inside. If you close up the soundhole, you'll lose quite a bit of volume just for that reason.