The source SL is the sound pressure level expressed in dB referenced to 1 m away from the acoustic center of the sound source.
What determines the SL of a single organ pipe?
Can SL be related to something like the acoustic volume velocity or volume displacement? Is there a mathematical relationship of dependence between SL and one or more generalized source-characterizing parameters like these.
Can the SL for a given pipe be increased or decreased without making physical modifications to the pipe? How is SL then changed?
is there a good reference dealing with the SL from organ pipes? I cannot find one.
Thanks!
Ronald
Hi Ronald
Angel's advice surely is good advice.
Here are some online resources as well
https://newt.phys.unsw.edu.au/music/flute/
http://www.markshep.com/flute/Acoustics.html
As you were speculating - a main mechanism in flutes is the volume velocity (monopole) type source.
Flutes and organ pipes need a flow instability to trigger the volume velocity modulating mechanism.This is the function of the edge you blow across in a flute where, flow can either leave the flute or pass through the flute. Move this edge to a stable flow position and it becomes harder to generate a tone.
Hope this helps
Claes
Thanks so much for excellent responses. The reference that you provided Ángel is very interesting!...estimated 1% power efficiencies. My application is for generation of signals underwater, possibly using an organ pipe of sorts for narrowband low frequency signals, whose dynamics would first have to be roughed out in a regime of technical plausibility. Thanks again.
Ronald
Hi Ronald
As a sidenote, the efficiency of a loudspeaker in creating sound usualliy is about 0.5%, i.e. 5E-3. As a reference, most naturally occuring processes land in the ballpark 1E-5, so 5E-3 is not a bad efficiency.
Valves are reported to create sound inside of pipes with an efficiency varying from 1E-3 (a noisy valve at a poor point of operation) to 1E-8 (a very quiet valve).
However, the radiation factor tells us that resonant sound radiation has 100% effciency in radiating sound (discounting mechanical losses).
For radiation of structureborne sound this happens when the bending wavespeed exceeds the acoustic wavespeed, i.e. when so called coincidence occurs.
There are some honeycomb panel speakers (coincidence occurs at fairly low frequency for honeycomb) that use this principle and they achieve much higher effciency than ordinary loudspeakers. https://en.wikipedia.org/wiki/Distributed_mode_loudspeaker
A former collague of mine (Sven Tyrland) told me that he was able to get 50% efficiency and a very directional sound when using an matrix of many small speakers placed in a large wall without backing. Sven was very skilled and quirky - he told me that the trick was to mimic coincidence conditions.
If memory serves me correctly, I believe he mentioned phasing not being very fancy as he simply wired the speakers in serial/parallel to get a suitable impedance for the amplifier to drive.
This sound wall was used on discotheque and similar. He used it also outdoors and told me he was able to focus sound to very high sound pressure levels at long distance without any side disturbance, i.e. you could stand more or less next to it and have very high SPL in front of it.
So, perchance, if efficiency greatly matters - you might want to take a look at matrices of many small units spaced such that you meet the sampling criterion, i.e. exceed 4 speakers per wavelength?
Just my 2 cents
Claes
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