Planning Space for Pipe Organs: Acoustics

Planning a room with good acoustical properties is important, not only for the pipe organ but for all music (instrumental or choral) and the spoken word. To insure the desired results, it is often wise to retain the services of an acoustical engineer. Look for one who understands the requirements of successful musical acoustics as well as clear speech intelligibility. Seek out one who has demonstrated that understanding in church buildings you can visit.

It is important to plan for a room that has pleasant, responsive, resonant acoustical properties. An even reverberation time of 2 - 3 seconds with the building half occupied is a practical goal. While it is possible to build a successful instrument in conditions less favorable than this, it is not the most desirable situation. One general rule to achieve this is to allow a minimum of 250 cubic feet of volume for every person. A room should be equally responsive in all frequency ranges.

The acoustic response of the room is determined initially not only by its cubic volume, but also by its shape and its materials. A rectangular plan with high flat ceiling is best. Sidewalls which are too low not only reduce cubic volume but force undesirably low positioning of the organ pipes.

Hard reflective surfaces (floor, walls, and ceiling) will promote better sound reflection. Choose all finish material carefully. Sound absorbing material (pew cushions, carpet, etc.) should be avoided. Floor surfaces of hardwood, concrete, tile or marble are most desirable. Walls of stone or smooth brick are ideal. Generally, the more solid the material, the better the results. Ceilings should also be hard surfaced. Porous materials should be avoided. If such material is desirable for visual reasons, it should be sealed with a polyurethane sealer. It is especially important to provide rigid materials near the choir and organ areas. This will contribute greatly to the total effect of the room. Sound diffusion, the desirable, even distribution of sound throughout a room, is in part created by architectural details such as pilasters, beams, moldings and reveals. Irregular wall and ceiling surfaces also promote sound diffusion and should be incorporated into the design of a room if possible.

Remember the following points in planning a good room: Plan for responsive acoustics with a natural reverberation. Surfaces (floor, walls, ceiling) should be constructed of solid, hard, acoustically reflective materials with sound diffusing elements. Avoid sound absorbing materials. Minimum cubic volume = 250 cu. ft. per person.