Acoustics for Worship Spaces
Acoustics for Worship Spaces
Summary of this essay
- Two understandings of worship: participating and observing
- Absorbent materials, especially carpet, discourage congregational participation
- Scientific measurements and acoustical consultants
- Using microphones
- Suggestions for building materials
Music in Worship
There are two understandings of worship. The first sees God as the audience, with congregation, choir, and clergy as participants. It emphasizes objectivity, group participation, natural acoustics. The second sees the congregation as an audience to be convinced, taught, moved, or entertained. It emphasizes subjectivity, individuals up front, solos, applause, the word "I", and electronics.
The ideal acoustic varies with the understanding of worship. However, the fact of the matter is that most services involve both understandings of worship, and the room should be designed for both participation and clarity.
Auditorium or Worship Center?
An auditorium has only one acoustical function, and that is to project music produced on stage so that the audience can hear it clearly. A room used for worship, on the other hand, has two acoustical functions. The first is identical to that for auditoriums: to project the sound produced by the choir, soloists, instruments, and preacher. The second function is to provide an atmosphere which encourages and supports congregational singing. Both acoustical goals must be met if the building is to be successful for worship.
Congregational singing is the most important church music, and the most important function of the organ is to lead and inspire the congregation in singing. For the congregation and organ to do their jobs well, they must have a suitable acoustical environment.
Acoustics suitable for worship are different than those for a living room, fellowship hall, or shopping mall. Carpet, for instance, can make a living room intimate and a fellowship hall quiet. But that same carpet in a worship room is as harmful to singing as an open window is to air-conditioning.
Individuals want to join in singing if they feel the company of their fellow worshipers. Individuals will not participate if they feel conspicuous and alone. It is important, therefore, that surfaces near the congregation be non-absorbent so that individual members can hear the rest of the group singing.
Padded pew backs, padded walls, drapes, and carpet should be avoided. Even the carpet in aisles hurts the transmission of sound from one side of a congregation to the other. It also interferes with the congregation’s hearing of the choir, as the aisle is one of the main channels of sound from the chancel (stage) down the length of the building.
Aisle carpet may cover only a small portion—say 15%—of the total floor area. However, that 15% is a very important 15% for reasons of sound transmission, because people already cover the other 85% of the floor. Carpet under the pews is sometimes advocated as a way to provide the same acoustics whether there are few people or a large crowd. The choir and organ may sound the same whether the floor under the pews is covered by carpet or by people, but the carpet will inhibit congregational singing.
When we sing we produce aural, sonic energy. It is counterproductive to have that energy absorbed. To sing in an absorbent room is as frustrating as to look at pictures in a room painted black. To sing in a live room is to experience the same joy which worshippers experienced during all the previous centuries when the great hymns were written.
Individuals are more likely to join choirs if the room is acoustically suitable for their work. They won’t sing if they can’t be heard. The choir’s effect is greatest when its music sounds best.
A choir needs solid, stiff walls behind and at each side, a hard floor underneath, and a hard ceiling above. Also, a congregation can hear a choir better if the floor, walls, and ceiling between the choir and congregation are not absorbent.
Lively rooms and lively music encourage young people; dry rooms intimidate them. Recording artists recognize the importance of ambience to sound: they add synthetic reverberation to their recordings.
Children and parents feel uneasy in a room where each sound seems exaggerated due to the absence of background sounds from the congregation.
It is hard to hear a preacher whose energy is absorbed rather than radiated. It is artificial, and finally discouraging, to hear the voice only through loudspeakers. It feels more natural, and our response to the words is greater, if we can hear the natural voice. A preacher needs solid walls, floor, and ceiling.
For acoustical advice, a church should turn first to a well-trained church musician who has actively listened in a variety of buildings and who knows how to encourage congregational participation. A church may also want to employ an acoustical consultant. The consultant will attempt to provide acoustics which fit that church’s understanding of worship. It is important, therefore, that the church think about and verbalize its goals to the consultant. The consultant should not tell the client what is needed separate from specific worship goals.
Most acoustical consultants work in industry, such as designing sound-deadening for noisy machines. It is important for a church to find a consultant who is knowledgeable about music and the psychology of congregational participation.
Beware the expert who says there is one ideal acoustic for all uses or who is selling sound equipment.
Organists usually ask for a long reverberation time because it enhances the effect of the organ. Preachers, though, usually want a short reverberation time, as reverberation is associated with garbled speech. The fault, however, is usually not too long a reverberation time but a pronounced resonance at a single frequency. The goal should be to build a room which has an even response to all frequencies and which has no resonant points.
There is a technical detail to be observed at this point: most buildings reverberate more at low frequencies than at higher ones, and it is these low frequencies which are most helpful in supporting congregational participation.
Speech intelligibility and amplification are improved by placing a solid surface behind and above the speaker (preacher). We see from pictures of very large buildings built before the time of electronics that pulpits always had a solid wall behind and a canopy above. They were never free-standing, distant from a reflective back wall. It is more important to have such reflective surfaces than it is to have the speaker close to the listeners. All of these considerations apply equally to singers.
Lay persons hear only about half of what acousticians measure. That is, if an acoustician says a room has 4 seconds reverberation, the ordinary person would say the same room has about 2 seconds, based on what is actually heard with the ears. The reason for the difference is the way reverberation time is measured.
Reverberation time (R.T.) is defined by acousticians as the length of time it takes a sound to decay 60 decibels. 60 decibels above the background noise level of a building is a very great amount. Acousticians fire a pistol or burst a balloon to generate a sound 60 decibels above the background noise level. Such a sound is roughly 2 times louder than a hand clap, and the R.T. measured or estimated by an acoustician is roughly 2 times greater than what we as lay persons hear.
Electronic devices are not nearly as sensitive as human ears. We can clearly hear the negative effect carpet has on congregational singing, but that effect is impossible to measure electronically.
What a Church Should Ask For
- Hard and stiff floor, walls, and ceiling;
- No carpet, drapes, or "acoustical" ceiling (when this term is used to mean a sprayed-on absorbent material.)
- Hard and stiff walls behind the organ, choir, and preacher.
- Organ and choir located on the central axis of the building and singing directly toward the congregation.
- Organ pipes placed in a free-standing wooden case with the largest ranks on the front and the smallest ranks behind.
- Respect for the musician’s position as a person knowledgeable about sound. The church’s music is, indeed, sound of the highest order and importance, and its musicians deserve the greatest respect.
Microphones and Public Address Systems
The goal for acoustics in the worship space is for communication, both music and speech, to be as natural—as human and genuine—as possible. Since electronic amplification, no matter how well done, adds artificiality, it is good if the room is planned so as to require little electronic assistance. An important way to lessen the need for amplification is to provide solid, hard, reflective, non-carpeted surfaces beneath and behind the choir and preacher. These help to reinforce and project sound to the congregation, as does a solid, reflective ceiling.
Speech augmentation requires a different kind of sound system than does music reproduction. For speech, only the middle and high frequencies need to be amplified. Music reproduction—tapes and CDs—requires amplification of all frequencies, which calls for different speakers and different equalization.
To Make Amplified Speech Sound Natural
- Place speakers near the pulpit so that the congregation hears sound coming from the direction of the pulpit.
- Use "notch filters" so that amplifier does not amplify those frequencies at which the room is resonant.
- Amplify only the mid and high frequencies, the ones important to clarity of speech.
- Do not amplify the choir. It always sounds artificial. Also, accurate amplification would require many microphones.
Ways To Improve Non-Amplified Sound
- Solid (stiff, firm, non-absorptive) floor between preacher and choir and congregation.
- Solid wall behind choir. Helps to project sound toward congregation.
- Solid wall behind pulpit.
- Solid ceiling above choir and pulpit.
Suggestions Regarding Building Materials
Walls must be stiff if they are not to absorb the long wavelengths of low frequency sound. Use two layers of 5/8" sheetrock instead of one. Use wide studs closely spaced—the taller the wall, the wider the studs. Thin (¼") wall paneling should be glued to 1" material. Otherwise, it absorbs low frequencies.
Foot noise is not a problem on solid floors such as those of masonry, but it often is objectionable on suspended wood floors which act like a drum head. Rather than install carpet, make the floor solid: use two layers of underlayment instead of one; install fiberglass insulation board between the floor layers; place the joists closer than normal.
If carpet is inevitable, use thin, tightly-woven carpet without padding.
Suspended ceilings absorb a great deal of sound. The rough surface absorbs high frequencies; the fact that the panels are small (2′ x 4′) and loose means they absorb low frequencies. That is good for a supermarket. It is fatal to group singing.