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Don’t let your multipurpose room sound like a train station

Planning helps churches create better acoustical conditions in multipurpose rooms.

By Richard A. Honeycutt

Churches often complain about the noisiness of their existing multipurpose spaces. While optimizing the acoustics of a single space for multiple functions poses a challenge, careful planning in the design phase or during a renovation can enhance the room’s acoustics.

Common uses for  multipurpose rooms include the following:

  • Fellowship meals
  • Meetings, with or without featured speakers
  • Worship with hymn singing
  • Dramatic and/or musical performances
  • Recreation

While no single set of acoustical conditions is ideal for all functions, we can control certain ones. An important consideration for sound control is background noise from outside, adjacent rooms, the HVAC system, or from the occupants. These extra sounds can make the room uncomfortable.

Another consideration is reverberation time (RT): The time required for a sound to decay to inaudibility. A long RT causes sound to linger, contributing to overall noise and the harder it is to be understood while talking.

Speech intelligibility

Both background noise and RT affect speech intelligibility. During fellowship meals people prefer privacy between different table conversations, which technically is low intelligibility. During large meetings, everybody wants to understand the facilitator, which requires high intelligibility.

Related to speech intelligibility is acoustical strength, or room gain, defined as how much louder a sound is within the room than that same sound would be outdoors.

Echoes are another acoustical challenge. Echoes are related but not identical to reverberant sound, or sound reflected repeatedly, producing a continuous jumble of sustained noise. Echoes of individual words are recognizable as words; whereas, reverberation is not recognizable as the individual sounds.

Despite the common misconception that acousticians
 do nothing but recommend absorptive wall panels, a skilled practitioner will use several strategies to meet the acoustical, aesthetic, and budgetary goals of the church.

Noise is most easily controlled at the design stage. A common source of excess noise is HVAC systems. If these are designed appropriately, choice of equipment and layout can provide noise control. Improving HVAC noise levels after a room is built will entail more limited choices and higher costs. The best solution for a given room depends upon the room and system design.

Noise from external sources is also best controlled at the design stage, by proper room layout and optimum wall, ceiling, window and door design.

Reverberation time

Reverberation time depends upon the volume of a room and the acoustical absorption of its surfaces. Ideal RT varies from about a half second for a meeting or  lecture to about two seconds for traditional worship. The combination of traditional worship and concert use with fellowship meals and lectures create conflicting requirements for RT. Contemporary or Gospel worship styles work well with RT similar to the target values for lectures, meetings, and eating functions. There are a few good electro-acoustical solutions to provide variable RT in a room but the cost may be prohibitive.

For both amplified and unamplified speech the background noise level, reverberation, and sound level of the desired speech control the intelligibility. For unamplified speech, reflective surfaces in the room near the person speaking help to support the speech sound level, and thus improve intelligibility. This is why a reflective ceiling helps people to understand what is said in large meetings and dramatic presentations. A reflective shell above the stage area is helpful for unamplified speech and vocal or instrumental music. If reverberation control is achieved by placing absorptive materials on the upper walls, a reflective ceiling may be used, achieving good conditions for unamplified speech without excessive reverberation.

For amplified speech, a well-designed sound system is necessary. Normally, this will consist of a single speaker system mounted high and in front of the audience, although some rooms need one or two line array speakers that spread the sound horizontally.

The preferred acoustical strength ranges from low for a dining function to high for open meetings. One solution is designing the room to have low strength for peaceful dining, then adding a good sound system with a wireless handheld microphone for open meetings.

The importance of unamplified sound

For some performance and worship styles, natural unamplified sound is important. Even when amplification is used, it is not fool proof: Johnny may forget to turn on his wireless mic during the Christmas pageant, or Sally’s wireless mic may fail just before her only line. In these cases, good strength is needed to help t hem project sound acoustically. Good strength is also needed for hymn singing. Most people feel uncomfortable if they hear only themselves singing. A reflective ceiling makes others’ singing audible. Where a reflective ceiling cannot be used, a good sound-system designer can lift the choir in the sound system so that the congregation is encouraged by the choral sound.

Echoes cause problems mainly when they occur over 1/20 second after the original sound, and when the echo is as loud as the original sound. In a 120’x 80’ x 36’ multipurpose room, a sound from the stage requires about 106 milliseconds to travel to the back wall, then about 100 milliseconds  to return to the ears of a person seated on the front row. This is a delay of about 1/5 of a second, well over the 1/20-second limit. Unless the back wall is covered with acoustically absorptive material, or acoustical diffusion, which breaks up echoes by scattering the reflected sound, the echo can be annoying and/or distracting.

If you are planning a multipurpose room, get a competent acoustical consultant involved at the schematic design stage. Avoiding problems is much less expensive than correcting them later. You can negotiate with your architect whether the consultant’s fee will be included in the architect’s charges or will be billed directly to the building owner.

If you have problems with an existing room, most consultants can offer a proposal tailored to the scope and difficulty of the work. The consultant does not “fix” the acoustics. They analyze the acoustics of the room and makes appropriate recommendations. A general contractor usually must be engaged to make any changes in the room. If HVAC noise is a problem, an HVAC contractor may be needed. Once a consultant provides estimates of the costs for each noise-control modification, you can decide for which steps you will request bids from contractors.

Richard A. Honeycutt is principal consultant, EDC Sound Services, Lexington, NC. www.edcsound.com

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