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MusingMuso

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But surely the metal expanding in both directions will make there even more room inside the pipe? However I guess that while the pipe will get longer (leading to a flattening of pitch) it will also become of wider scale (which due to increased end effect will sharpen pitch)?

 

But I think the main point is that pipe dimensions are not the dominant effect. The reduction in density of the air is far more significant, and therefore results in an overall sharpening of pitch.

 

JJK

 

I seem to remember from my Physics studies that it was basically the length of a flue pipe governed the pitch - not the volume of air inside it.

 

FF

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I seem to remember from my Physics studies that it was basically the length of a flue pipe governed the pitch - not the volume of air inside it.

 

FF

That was certainly my understanding, in which case the argument, if I've understood it, that the metal of a pipe would expand both inwardly and outwardly is irrelevant. I just don't understand why expansion of a metal flue would cause its tuning to go sharp.

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The frequency a pipe produces is proportional to the speed of sound divided by the length of the pipe. Increasing the speed of sound increases the frequency, because the waves get from one end of the pipe to the other in a shorter time.

 

The approximation that only the length of the pipe is involved is fine provided you are comparing the pitches of various pipes in a body of air that is all at the same temperature and pressure. Once you allow the temperature and pressure to vary, as it does from day to day, you have to take into account the effect of the speed of sound.

 

If, as the temperature rises, the proportion by which the speed of sound increases is greater than that by which the pipe lengthens, the pitch will rise. This will normally be the case, because the speed of sound increases by 3.5% between 0C and 20C, whereas a pure tin pipe will have lengthened by only 0.06%.

 

A pipe will expand in diameter by the same proportion it expands in length. Thus, to a first order approximation, its scale won't alter.

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The frequency a pipe produces is proportional to the speed of sound divided by the length of the pipe.  Increasing the speed of sound increases the frequency, because the waves get from one end of the pipe to the other in a shorter time.

 

The approximation that only the length of the pipe is involved is fine provided you are comparing the pitches of various pipes in a body of air that is all at the same temperature and pressure.  Once you allow the temperature and pressure to vary, as it does from day to day, you have to take into account the effect of the speed of sound.

 

If, as the temperature rises, the proportion by which the speed of sound increases is greater than that by which the pipe lengthens, the pitch will rise.  This will normally be the case, because the speed of sound increases by 3.5% between 0C and 20C, whereas a pure tin pipe will have lengthened by only 0.06%.

 

A pipe will expand in diameter by the same proportion it expands in length.  Thus, to a first order approximation, its scale won't alter.

Oh dear, many thanks for trying to explain. I did pass A-level physics, quite some years ago, but I think I'll have to go and sit in a dark corner now!

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I seem to remember from my Physics studies that it was basically the length of a flue pipe governed the pitch - not the volume of air inside it.

 

FF

 

In which case, how could one account for the fact that the longest pipe of the monster-sacled 'Flute' 16p on the Pedal Organ at Gloucester Cathedral is but thirteen feet in length, yet sounds CCC in just intonation?

 

I doubt that this rule apply only to metal pipes - (i.e., that of the pich being governed by the length of the resonator as opposed to the volume of air contained therein).

 

:)

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In which case, how could one account for the fact that the longest pipe of the monster-sacled 'Flute' 16p on the Pedal Organ at Gloucester Cathedral is but thirteen feet in length, yet sounds CCC in just intonation?

The width of the pipe also has a part to play in the physical explanation.

 

Paul

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The frequency a pipe produces is proportional to the speed of sound divided by the length of the pipe.  Increasing the speed of sound increases the frequency, because the waves get from one end of the pipe to the other in a shorter time.

 

The approximation that only the length of the pipe is involved is fine provided you are comparing the pitches of various pipes in a body of air that is all at the same temperature and pressure.  Once you allow the temperature and pressure to vary, as it does from day to day, you have to take into account the effect of the speed of sound.

 

If, as the temperature rises, the proportion by which the speed of sound increases is greater than that by which the pipe lengthens, the pitch will rise.  This will normally be the case, because the speed of sound increases by 3.5% between 0C and 20C, whereas a pure tin pipe will have lengthened by only 0.06%.

 

A pipe will expand in diameter by the same proportion it expands in length.  Thus, to a first order approximation, its scale won't alter.

 

 

===================

 

 

Yeah, yeah yeah!

 

This is all well and good, but it doesn't explain what happens when I blow into my hideously unattractive Maltese glass vase, which is apparently worth money for some strange reason.

 

It has bulbous base, a bit like a laboratory-flask, but sort of box-like, without being completely square. The neck is very narrow.

 

Obviously, being a vase, it is a stopped pipe.

 

The "thing" is no more than about 12" high, but when I blow into it, I'm getting a note of 8ft CC#; and the quality of sound is quite superb. I could quite easily live with a whole rank of these vases as a pedal Bourdon.

 

Have I discovered a new type of space-saver Flute?

 

MM

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===================

Yeah, yeah yeah! 

 

This is all well and good, but it doesn't explain what happens when I blow into my hideously unattractive Maltese glass vase, which is apparently worth money for some strange reason.

 

It has bulbous base, a bit like a laboratory-flask, but sort of box-like, without being completely square. The neck is very narrow.

 

Obviously, being a vase, it is a stopped pipe.

 

The "thing" is no more than about 12" high, but when I blow into it, I'm getting a note of 8ft CC#; and the quality of sound is quite superb. I could quite easily live with a whole rank of these vases as a pedal Bourdon.

 

Have I discovered a new type of space-saver Flute?

 

MM

 

No not a new kind of flute, Compton used cubes for example.

The principle is that of the Helmholtz resonator, example an 'ocarina'.

 

These links might help:-

 

http://www.phys.unsw.edu.au/~jw/Helmholtz.html

 

http://physics.kenyon.edu/EarlyApparatus/R..._Resonator.html

 

Good fun playing with bottles and water to get different pitches!

 

David W

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No not a new kind of flute, Compton used cubes for example.

The principle is that of the Helmholtz resonator, example an 'ocarina'.

 

These links might help:-

 

http://www.phys.unsw.edu.au/~jw/Helmholtz.html

 

http://physics.kenyon.edu/EarlyApparatus/R..._Resonator.html

 

Good fun playing with bottles and water to get different pitches!

 

David W

 

=====================

 

 

Well, you learn something new every day!

 

This means that every organ could have a 32ft rank of earthenware pots, including house organs.

 

I can well imagine that bottles and water can be fun, but why on earth should anyone wish to use water?

 

MM

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It's been done:

 

http://www.petersontuners.com/news/bbo/index.cfm

 

I think they use mineral oil - which doesn't evaporate - instead of water... but it must work on the same principal.

 

I might be displaying gross ignorance here but when Mozart wrote for "glass harmonica" wasn't that effectively the same principle?

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I might be displaying gross ignorance here but when Mozart wrote for "glass harmonica" wasn't that effectively the same principle?

 

No, that was a series of rotating glass bowls, working on the same principle as stroking the rim of a wine glass with a damp finger!

 

A shame that this instrument is not used any more - it is a very haunting, yet pleasing sound.

 

John

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No, that was a series of rotating glass bowls, working on the same principle as stroking the rim of a wine glass with a damp finger!

 

A shame that this instrument is not used any more - it is a very haunting, yet pleasing sound.

 

John

 

 

===========================

 

 

I've always said, that if people must make digital combination organs, this is one sound which should be included.

 

A Sonata for Glass Harmonica and organ sounds a wonderful idea.

 

MM

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Yes - so this is surely therefore directly connected to the cubic capacity of the pipe in question (with regard to the volume of air)?

 

====================

 

But what about altitude, barometric pressure, and relative humidity?

 

I don't really want to know, I just want to give Nick Bennett mathemtical grief!

 

B)

 

MM

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Yes - so this is surely therefore directly connected to the cubic capacity of the pipe in question (with regard to the volume of air)?

 

====================

 

But what about altitude?

 

Surely, the higher the pipe, the more the effects of altitude?

 

I don't really want to know, I just want to give Nick Bennett mathemtical grief!

 

And when he's done that, perhaps he might consider the effect on humidity of the adiabatic lapse-rate on terraced werkprinzip layouts.

 

B)

 

MM

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.... and in English, that would be?

 

.... B)

 

Actually MM, I have never been in Gloucester Cathedral when it was hot enough for this to have an effect. In addition, since most of the soundboards are positioned at the same height (only the GO being on two levels), there seems to be little difference in the pitch/tuning relative to the altitude of the pipe-work (and consequent temperature differential).

 

However, the tuning of at least one instrument of my acquaintance is directly related (so it would appear) to the humour of the Verger - and whether or not there have been any lesbians present in the building during the previous twenty-four hours.

 

B)

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However, the tuning of at least one instrument of my acquaintance is directly related (so it would appear) to the humour of the Verger - and whether or not there have been any lesbians present in the building during the previous twenty-four hours.

 

B)

 

==================

 

Be very careful "S".....I used to have stand-up rows with Peter Tatchell in London; usually whilst shopping in the Asian-owned deli.

 

I told him I didn't approve of naming and shaming people, but I could turn nasty!!

 

B)

 

MM

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.... and in English, that would be?

 

.... B)

 

B)

 

==================

 

The adiabatic lapse rate, is the rate at which water vapour is shed and precipitation ensues as altitude increases, due to the cooling of moist air.

 

In other words, if it's snowing on your kronwerk, it's probably just foggy around your brustwerk, or vice versa, in which case you may well expect there to be thunder and lightning.

 

MM

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  • 2 weeks later...
Guest Andrew Butler
However, the tuning of at least one instrument of my acquaintance is directly related (so it would appear) to the humour of the Verger - and whether or not there have been any lesbians present in the building during the previous twenty-four hours.

:lol:

 

Do they generate heat, or have a refrigerative effect? :lol:

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