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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 in
by 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 agoEnergy 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 agoMy 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 agoSound 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 agoFrom 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.
- CarVac 11y agoBowed instruments get around the attack/sustain tradeoff by having continuous energy input, so the attack strength can be sustained for the duration of a note. 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.
- CarVac 11y agoEnergy conservation doesn't come into play, because unlike on a plucked instrument, the bow is there continually supplying vibration. If more of it gets emitted, then more of the bow's energy goes into vibration instead of friction. 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.