Concerning pipes and sound

[Lausanne]

And just to add even more to Colin's accurate description of why a candle would not be extinguished at the top of a flue pipe: the sound wave in the pipe is a stationary wave. The air particles are moving backwards and forwards in the direction of the pipe length but are not flowing far enough to extinguish a candle flame. in other words, air is not constantly blowing out of the top of the flue pipe (in a reed it is, but that's probably going to be Stanley's next question!). Another way to think of sound waves is as slight increases and decreases of air density. The sound waves then travel away from the top and mouth of the pipe in all directions there is air, but the air is not flowing towards the listener, your ear just detects the changes in air density.

It is hoped that the original experiment was performed with a pipe placed horizontally with its mouth facing to the side, so the candle flame would always be at right angles to both the direction of flow of air at the mouth and the direction of the sound wave's amplitude at the open end of the pipe.

I'm glad somebody mentioned the obvious sound absorbing properties of wood, particularly lanterns. There are two main material properties that govern sound reflection:

1. The rigidity - so that as little energy is lost from the sound wave in moving the wood/plaster panel or window as it reflects.

2. The surface roughness - this has the effect of sending some of the sound waves off in different directions resulting in destructive interference.

Then of course there is the shape and size of every possible part of the building, fixed and moving which effects how far different sound frequencies travel. This just highlights the overriding importance of the building on the sound of any organ.

But still so many churches just love their thick wall-to-wall carpet - hence we make the tubas even louder!

[Rowland Wateridge]

Professor Wilkes’ notes on “The production and control of sound in organ pipes” run to eight pages with numerous diagrams and technical data all beyond my comprehension, but there is an illustration of the candle experiment.  The open flue pipe is shown in the vertical position.  At the top of the pipe, the candle is held horizontally, i.e., at 90 degrees, with the flame positioned centrally above the open end, and somewhat below that there is a cardboard collar positioned around the body of the pipe.  The candle remains lit.  The candle is then held vertically with the top of the flame level with the lower lip of the mouth, and the flame is extinguished.  I stress that this is the diagram, and to the best of my recollection this was the orientation of the pipe and candle during the experiment.  The venue did not have a pipe organ, and after this length of time (22 years) many of the details, for example, how the pipe was blown, are now hazy to me.  There is data not only about reeds but also different members of the reed family.  How to interpret those details is now totally beyond my recall, and so these comments may not be particularly helpful.  It’s clearly a complex subject.

In most basic amateur or lay terms, Stanley’s question was about emission of sound from pipes, not necessarily the same thing as production of sound, I assume.  Further elucidation from you or Colin Pykett would be welcome.

[Colin Pykett]

I don't think I can add much to what I said previously, but would like to emphasise should there be any doubt that in no way was I intending to slight or criticise Professor Wilkes.  In fact his lecture sounds very interesting and I wish I had been there to enjoy it.

[Stanley Monkhouse]

Thank you all. I'll ponder the responses. I'm not sure that all my questions are answered, but I'm not sure they will ever be. Over the years, I've read that screen organs with soundboards running N-S project sound down the nave better than those with soundboards E-W. Where's the evidence? I've read about reflected sound as opposed to direct sound - which implies that the sound is predominately from a small area of the pipe circumference which might be so in flues but not reeds. I once read that the high pitched Great mixture at Durham introduced in Conrad Eden's day helped the sound to reach down the nave bringing the rest of the Great with it. This sounds like poppycock to me. A great deal of what is written about rebuilds/restorations falls into the genre of self-justification, especially when written by the consultant concerned - whose hearing may or may not (as mentioned earlier) be defective. I remember Mr Clutton waxing lyrical on the different approaches he recommended at Ely and St Paul's back in the day, and thinking that he sounded like a snake-oil salesman. It's all very entertaining. 

[Lausanne]

On 24/06/2020 at 00:44, Stanley Monkhouse said:

 At Southwell, by no means high or wide, the old HNB organ on the screen was hopelessly inadequate in the nave, despite the Great then being on the west side and Swell shutters opening west. This was said to be part of the reason for the installation of the separate organ in the nave triforium. It was also said (Ken Beard I think) that the lantern swallowed up the sound. And yet the lantern at Southwell is puny compared to say that at Ripon where there is not the same problem. And at York and Lincoln the lanterns are gigantic, yet the organ sound penetrated the enormous naves, though not well, better than at Southwell, IMO. Type of stone? Southwell, York and Ripon all have wooden nave roofs. (I'm talking of York organ 1960 to 2019). 

I feel that all your questions were answered by Colin most specifically, but perhaps you might accept a little more acoustics relating to how the lantern at Southwell manages to 'swallow' sound. As sound radiates in all directions, only that travelling in a direction through the relatively low arch on the other side of the crossing will be heard in the nave. The sound that hits the wall either side and above the arch will be reflected both into the east and west transepts and up into the lantern. As the dimensions of the crossing are both low and narrow, the sound will make several reflections before just possibly finding a direct path back into the nave and have lost most of its energy.

[Christopher Brown]

Part of the problem at Southwell compared with some others mentioned is the acoustic asymmetry of the building. Apart from the crossing you have a long dry nave on one side and a more intimate and reverberant chancel on the other. If you did manage to voice an organ on the screen to have impact in the nave it would then be intolerably harsh in the choir. Lincoln, York etc still have the issue of the organ being off centre, but because the buildings themselves are relatively symmetrical the organist and organ builder between them can overcome the difficulties well enough for a single organ to be viable

[John Robinson]

7 hours ago, Christopher Brown said:

Part of the problem at Southwell compared with some others mentioned is the acoustic asymmetry of the building. Apart from the crossing you have a long dry nave on one side and a more intimate and reverberant chancel on the other. If you did manage to voice an organ on the screen to have impact in the nave it would then be intolerably harsh in the choir. Lincoln, York etc still have the issue of the organ being off centre, but because the buildings themselves are relatively symmetrical the organist and organ builder between them can overcome the difficulties well enough for a single organ to be viable

Yes, the same problem was mentioned quite a while ago with regard to York: the organ being loud enough to fill the nave would be overwhelming in the choir.  I think it was probably Francis Jackson.

I don't doubt the great man's words, but organs need not always 'roar', surely?    I have often thought, and of course I stress that I am no organist or expert, that it must be possible to select appropriate stops to handle a nave full of people, yet to choose fewer stops to accompany a smaller number of people in the choir.
Of course, if both choir and nave are used concurrently, the problem may be more difficult, but how often is this actually the case?  I understood that (at York anyway) services and recitals are usually held in the choir OR the nave.

Am I mistaken?

[ajsphead]

7 hours ago, John Robinson said:

Yes, the same problem was mentioned quite a while ago with regard to York: the organ being loud enough to fill the nave would be overwhelming in the choir.  I think it was probably Francis Jackson.

I don't doubt the great man's words, but organs need not always 'roar', surely?    I have often thought, and of course I stress that I am no organist or expert, that it must be possible to select appropriate stops to handle a nave full of people, yet to choose fewer stops to accompany a smaller number of people in the choir.
Of course, if both choir and nave are used concurrently, the problem may be more difficult, but how often is this actually the case?  I understood that (at York anyway) services and recitals are usually held in the choir OR the nave.

Am I mistaken?

How wonderful if this was the case in the UK. Unfortunately many of our instruments in larger buildings simply do not possess the ability to roar down the main axis of the building and flood the space with sound. Our European and U.S. brethren seem to be far less regularly afflicted. It's always possible to use fewer stops, but once you've maxed out barring the Tuba that's about it.

[Christopher Brown]

21 hours ago, John Robinson said:

Yes, the same problem was mentioned quite a while ago with regard to York: the organ being loud enough to fill the nave would be overwhelming in the choir.  I think it was probably Francis Jackson.

I don't doubt the great man's words, but organs need not always 'roar', surely?    I have often thought, and of course I stress that I am no organist or expert, that it must be possible to select appropriate stops to handle a nave full of people, yet to choose fewer stops to accompany a smaller number of people in the choir.
Of course, if both choir and nave are used concurrently, the problem may be more difficult, but how often is this actually the case?  I understood that (at York anyway) services and recitals are usually held in the choir OR the nave.

Am I mistaken?

I think you're broadly correct. It's a question of degree - York will never be optimal from every listening position but it can be satisfactory given careful design and appropriate handling by the organist. The additional problems at Southwell mean a single organ is pretty much doomed to fail, hence the constant changes over the years and eventual bowing to the inevitable!