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A natural Aeolian organ pipe


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A strange title? Yes, partly because I couldn't think of a better one. There is such a thing as the Aeolian harp which emits sound of its own accord when the wind caresses its strings. and it was a similar effect which my wife and I came across yesterday while out walking on the South Downs.

 

We heard a distant, eerie yet compellingly beautiful sound as we approached a gate. It got progressively louder and it turned out to be generated by a gatepost made from a closed steel cylindrical pipe about four feet high and a few inches in diameter. It was pierced by three pairs of opposed holes at the top, middle and bottom which were presumably there to allow wires to pass through when performing its usual role as a fence post.

 

As the wind speed increased the pitch of the note rose abruptly by a fifth, and it dropped when the wind died away. We heard it emitting three separate notes at different times, an interesting demonstration of mode-switching. The timbre was that of a rather loud stopped diapason.

 

It was a fascinating example of organ pipe physics at work, and I intend to go there again to make some measurements of the pipe and also to record its sounds. It is also interesting that natural phenomena such as this (but generated by wood rather than steel tubes!) might have suggested simple wind instruments, and thus organ pipes, to our ancestors way back in pre-history.

 

CEP

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By extension, anyone who has transported organ pipes on a roof rack will tell you that it is a good idea - to say the least - to arrange them so that the feet face backwards, so as to "avoid a symphony on the M4" as one person put it.

 

Elsewhere, some pipes were being transported and met with an accident somewhere remote up in the hills. One got wedged by a gate-post and the place acquired a reputation for being haunted because of the unearthly sounds which could be heard when the wind blew.

 

When thou from hence away art past

Every night and all

To whinny muir thou com'st at last

And Christ receive thy soul.

 

Lyke Wake Dirge (Poem of the Yorkshire Moors, as set by Benjamin Britten et al)

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Loved the pun David (extension ... )

 

Maybe 'my' gatepost was actually the long-lost organ pipe you described?

 

The gate in my message was only a few hundred yards away from a nice old church with a not quite-so-nice organ (a very early Allen digital with a couple of small speaker boxes wedged high up in the chancel roof).

CEP

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Along the lines of organ pipes and cars, I remember a previous car I owned had a sun roof which, when open and travelling at certain speeds, produced quite a powerful and deep pedal organ note inside the car. It was hard to specify a distinct pitch, but I swear it was within the 32' octave.

 

How to produce a 32' pipe no longer than the interior of a small car! It brought to mind those 'cubes' I've read about.

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Along the lines of organ pipes and cars, I remember a previous car I owned had a sun roof which, when open and travelling at certain speeds, produced quite a powerful and deep pedal organ note inside the car. It was hard to specify a distinct pitch, but I swear it was within the 32' octave.

 

How to produce a 32' pipe no longer than the interior of a small car! It brought to mind those 'cubes' I've read about.

 

Yes, I've experienced that with an open car window. The enclosed air in the car acts as a Helmholtz Resonator. Other examples are bass reflex (ported) loudspeaker cabinets, and the ocarina wind instrument.

 

But car-sized organ pipes, while not being particularly long, would take up a lot of soundboard room!

 

CEP

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Yes, I've experienced that with an open car window. The enclosed air in the car acts as a Helmholtz Resonator. Other examples are bass reflex (ported) loudspeaker cabinets, and the ocarina wind instrument.

 

But car-sized organ pipes, while not being particularly long, would take up a lot of soundboard room!

 

CEP

Ah, but where there are height limitations... !

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