In the past 10 years, churches in the northern hemisphere have enjoyed an unprecedented boom, partly as a result of a re-emphasis in traditional values in light of the chaos plaguing society, millennial fears, and an upswing in spiritual and religious beliefs.

As a result of this growth, new churches are sprouting almost overnight in new and formerly un-reached communities; older facilities are undergoing extensive renovations and rehabilitation to bring them up-to-date with existing codes, advancing technology, and dynamic worship emphasis.

As an acoustical consultant and bi-vocational minister, I have often been asked what are the most important considerations going into the design of a facility, be it an existing facility or a new construction? The answer to this question covers a broad spectrum of issues such as:

* Site Selection and Location
* Acoustics vs. Worship Emphasis and Music Style
* Facility Use and Architectural Design
* Mechanical Noise & Vibration Control Site Selection and Location

For new constructions, the actual site selection and location of the building in relationship to its surroundings can be crucial from the standpoint of environmental noise. For instance, a worship building that is located along a major interstate highway, airport, or industrial hub may require additional sound isolation measures that include "beefing up" the building envelope design that would in turn impact project cost.

Typical mitigations may include heavier roof concrete slab, sound isolating drywall ceiling assembly below the roof construction, corresponding wall construction in the form of grouted masonry units, concrete, brick, or some combination thereof, acoustical glazing, etc.

Acoustics vs. Worship Emphasis and Music Style
Prior to any design, the project team should possess a clear understanding of the worship emphasis and music style of the church. While the contemporary church is mostly based on the models set by either Willow Creek or Saddleback Valley Churches, and are upbeat in their music style, many mainline denominations remain fairly traditional or blended in nature.

Churches where the primary emphasis is in the spoken Word or where music is purely reinforced, require a space that is not reverberant. Traditionally oriented churches where organ music, choral presentations, and orchestral music are jointly emphasized will benefit from higher reverberation time in the order of 1.60 to 2.0 seconds for warmth and envelopment.

Note however that speech intelligibility and optimal sound systems, conditions deteriorate past 1.70 seconds. Since 99.98 percent of all churches in North America employ some form of sound reinforcement system, the generally accepted acoustic measure is to design the worship space based on one of the criteria above.

However, this reliance on sound reinforcement has resulted in perceptual mismatch where live choral and orchestral performances appear artificial in large spaces. One solution to this problem is the use of Electronic Architecture that consists of an array of small loudspeakers and microphones carefully obscured in the architecture and controlled by sophisticated software to simulate sound reflections and reverberant time length.

The direct and secondary reflected sound paths in close proximity of the stage are picked up by microphones and are then processed, amplified and transmitted through the concealed loudspeaker system to simulate late or early arrivals, depending on the program mode it is set to.

With this system, the space is thus "programmable" with the ability to be set to symphony, speech, or music modes at the push of a button. Cost for this elaborate system is typically prohibitive and ranges from $100,000 to $400,000. Lastly, since the delineation between traditional style worship service and theatrical production is becoming increasingly vague, perhaps future church designs should incorporate variable acoustics systems that are widely used in multi-purpose performing art centers around the world.

This system would enable the room to be physically "tuned" according to its presentation mode. For example, during an organ recital the room would possess a longer reverberation time in excess of 2.0 seconds, whereas in sermons or A/V presentations, the room reverts back to a "dead" space with reverberation time of 1.50 second or lower.

The method by which this is accomplished includes retractable heavy velour drapes (32 oz./sq.yd.), reverberation chambers with operable doors similar to the Meyerson Symphony Center in Dallas, sliding acoustical panels or sound reflecting panels, etc.

Facility Use and Architectural Design
In order to optimize available resources, many churches such as 2nd Baptist Church's Excitement West in Houston resorted to a large hangar-type multi use space that can be partitioned into several quadrants for Sunday School, Worship, and Gymnasium use. This concept is problematic at best since issues regarding sightlines, sound isolation, acoustical treatment, sound reinforcement capabilities, video, and day-to-day logistics are often compromised.

Note that this statement does not preclude the possibility of all relevant issues being addressed and integrated into the overall design. The bottom line dollar cost often dictates which system is value engineered out of the project with a measurable impact associated with it.

For example, in medium to large venues of 2,000 seats and above, maintaining adequate sightlines to the stage and presentation screens are priorities. This requirement alone, dictates that the floor slopes down toward the stage and possibly raised riser seating along the perimeter of the space will be necessary. Compounding this design criterion with programming requirements for divisible rooms via operable walls, sound and video systems design, storage issues, etc., would grossly limit the optimal design criteria for the multiuse space and dramatically add to project cost.

With the increasing popularity of 90-degree, fan-shaped floor layout, consideration must be given to room acoustics beneficial for both natural sound projections from the stage (e.g., choir and orchestra) and congregational singing. Narrow floor layout of 70-degree or less provides a heightened sense of warmth, intimacy, and envelopment in music.

Another method in achieving sound projection and diffusion is through the use of articulated wall design in the form of radius or geometric panels that reflect sound throughout the space.

In addition to sound reflection and projection, control of reverberant energy build-up and flutter echoes are accomplished by treating two adjacent wall elevations with opposing parallel walls. Treat with sound absorbing materials, similar to fabric-wrapped fiberglass panels, or other acoustically rated products such as Tectum panels, spray-on cellulose, perforated wood or metal panels with fiberglass backing, etc. Too much or too little treatment can impact room performance.

We therefore recommend that the church and its design representative hire a qualified acoustical consultant who would provide a thorough acoustical analysis and determine treatment locations, impact on reverberant energy control, type of product, etc.

Mechanical Noise & Vibration Control
One remaining, often missed element in design planning is the impact of the building ventilation system. In many existing facilities, including several churches in which I have ministered or provided consultation in, mechanical equipment, noise impact, speech intelligibility, critical listening and comfort are often overlooked.

Typical problems include, a) proximity of mechanical units and transmitted noise through wall, ceiling-floor assemblies, b) duct borne fan noise, c) excessive airflow velocities and turbulence, d) structure-borne noise and vibration, etc. Careful planning and expert consultation is the key to ensuring that the mechanical system performs unobtrusively. Otherwise the cost associated in retrofitting existing systems is exponentially more restrictive.

Typical background noise criteria for churches range between NC-20 to NC-30. Noise Criterion or NC is a single number rating system that is based on a series of curves of known octave band sound spectra compared against a measured spectrum to determine the NC level of the space. In conclusion, if you are in the process of planning a new facility or renovating an existing one, we recommend enlisting the services of a reputable acoustical consulting firm such as those listed with the National Council of Acoustical Consultants at http://www.ncac.com or phone (973) 564-5859. ·

Paul L. Tan is a senior consultant with the Dallas-based consulting firm of Pelton Marsh Kinsella. He has nearly fifteen years of acoustical consulting experience from around the world. Notable projects to his credit include Central Christian Church, Saddleback Valley Community Church, Richardson Performing Art Center, American Airlines Learning Center, and the Monona Terrace Convention Center