Acoustical Considerations

The location of the organ and the acoustical environment of the room in which it is heard are at least as important as the organ builder's skill in determining the final results of an organ installation. Basically, the room in which the organ is played constitutes an essential part of its sound system, much as the sound board of a violin is an integral part of that instrument. Since the organ builder is only, in a way, adding strings to the sound board, his insistence on proper placement of the organ and on suitable acoustics may readily be understood.

So, in addition to the inherent tonal qualities that the organ must possess, two elements must be present: the room must carry the sound of the organ well and the placement of the organ must be favourable.

On the first element, the shape and height (preferably rectangular and high) of the room as well as the materials used play a most important role in the reverberation or the absorption of the organ frequencies which have a very large spectrum: from 32 to 8,000 cycles. Reverberation time should not be shorter than two seconds and should decay evenly within that spectrum. Projection of sound is assisted not only by height but also by the absence of obstructions and a favourable ceiling shape. Such architectural features as hammer beams, deep beams projecting down from the ceiling, towers or lanterns in the path of the sound, deep arches around the ceiling line, or sharp lowering of ceilings will impede good projection. It is generally easier to project sound in a high ceilinged building than in one which is low. We would add at this point that wall-to-wall carpet is among the worst enemies of good acoustics. If there must be carpeting, make it hard short twisted pile, with no underlay. Restrict as much as possible the surface where it will be installed and never put carpet in the organ or choir area.

The organ should speak directly down the main (longest) axis of the building. It should not be inside a fairly closed organ room. Organ placement very close to a large window can also bring problems of tuning instability because of possible temperature variations. HVAC outlets should never be installed inside the organ space or where they move air directly on the instrument. The organ should be situated close to the singers, preferably behind and above their heads.

We understand that the above information is rather brief and represents a somewhat ideal situation. We know that most pipe organs are installed in existing buildings with more constraints than described above. Therefore, because we are dealing in an important but complex matter, we urge consultation with an acoustician who has experience and recognized success in church work.

Copyright Casavant Frères 1997

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