The Persistence of Sound
By: Marlayna Glynn Brown
Your worship facility is the environment in which you transmit word, song and music to evoke mood, enhance worship and elevate the spirit.
These sounds aren't simply what you hear from your electronic sound system, but a direct result of the entire acoustical environment – reverberation, early and late reflections, echoes – all influenced by the shape, surfaces, furnishings and even what is behind the walls and ceilings of your facility. A major part of the acoustical environment is the "noise signature" of the space, which includes the sound the building systems generate as well as the sound the outside environment transmits inside.
Reverberation is the persistence of sound in a particular space after the original sound is removed. The environment's reverberation should be long enough to ensure that music sounds natural, but short enough to ensure that your spoken message is clearly delivered to the recipient. More important than reverberation is the timing of early reflections as heard by worshipers. Excessive reverberation, however, can be a major challenge for many worship facilities and the wrong type of correction, a disaster. Excessive reverberation, combined with high background noise and the wrong sound system speakers, equals a major disaster.
Unlike the spectrum of color where two or more sources can mix and create another pleasing light, sound from two speakers or sounds from one speaker but delayed through reflection or reverberation do not merge into one. Both original components can be distinctly audible, and a third sound can appear that can be bad or good. The genius lies in orchestrating a proper combination of sound.
A challenge exists then in creating a proper acoustical environment for your worship facility while balancing the proper reverberation time with early reflections to enhance and support the spoken word, electronic music, congregational singing or choral performance.
These different types of sound are most effectively delivered with different reverberation. For example, the spoken word requires a short reverberation time to ensure that each word reaches the ear of the worshipper clearly, without running into the next spoken word. Contemporary worship services, with amplified electronic musical instruments, also generally sound better with shorter reverberation. Yet pipe organs, often used in traditional worship, as well as congregational, and choral singing sound best with longer reverberation times. The challenge of the acoustician is to balance all of these needs and define the proper reverberation time with the proper amount and timing of beneficial reflections and properly integrated with the correct sound system.
Fast forward to 2006, when St. Mary's Cathedral experienced the completion of its restoration, and you are transported to a bustling city serving a metro population of more than one million, along with the accompanying din of air conditioning, heavy downtown traffic, lots of activity from night clubs, state offices and a very busy university.
The restoration—the end result of providing high speech intelligibility, clear music reinforcement and reproduction in this high reverberation facility—was a challenge Ken Dickensheets, the principal consultant of Austin-based Dickensheets Design Associates, undertook by first evaluating the noise levels within the Cathedral.
He discovered that the noise from the Cathedral's HVAC system, combined with the exterior traffic noise from the busy street, was excessively high. This combination of noise contributed to a major problem already in existence in the old Cathedral. The worshipers could not understand the pastor even from as close as 20 feet away. The low dynamic range, combined with the noise masking the speech, made it difficult, if not impossible, to understand the spoken word. More contemporary music used at folk masses was simply jumbled.
Dickensheets first addressed the problem inside the Cathedral by working with the mechanical engineer to modify the HVAC system to reduce the HVAC noise to a reasonable level. Noise and vibration control is a specialty offered by qualified acousticians, requiring a familiarity with both physics and mathematics. HVAC noise, as well as the interfering street noise, was reduced by almost 20dBA.
Next, Dickensheets designed a sound system that produces a high level of direct to reverberant sound energy (sound that is more direct) by utilizing a steerable line array to keep sound energy focused at the seating and away from the rear wall and ceiling. This sound system designed was particular to the Cathedral to both address the reverberation problems and to provide an unobtrusive appearance to blend with the restoration work.
The system, in combination with the reduced noise levels, now allow for worshipers to hear and understand the content of the services.
Using an Acoustical Consultant
The experience of many churches has shown that acoustical consultation, and the follow-through recommendations that are implemented, cost much less during design and construction than the cost of corrections and modifications after move-in. For instance, corrections to noisy mechanical systems to reduce noise levels to that required for worship often cost 10 to 15 times the amount that would have been spent if taken care of during the design phase. Acoustical corrections can range from thousands of dollars to tens of thousands of dollars and noise corrections can cost much more.
Regardless of the situation, an experienced, independent acoustical consultant will play a pivotal role in helping your church achieve the best results through a proper design that is centered on the needs of the project.
The overall desired result must be considered in combination with other physical needs of the building and the impact that such changes will have on things such as fire codes, facility maintenance, room lighting, heating and cooling, and so forth. For this and other reasons, it is important that the consultant be well versed and experienced in many areas. It is also important that he be independent; that is, not tied to any manufacturer as is the case of a contractor. The consultant must be able to make recommendations based upon what you need, not what he sells.
If your facility is not yet designed, an acoustical consultant can ensure that the results will be ideal. If your facility is not yet built, an independent acoustical consultant can help identify the severity of problems that will most likely occur, along with design solutions. If your built facility is experiencing sound problems, an acoustical consultant can suggest improvements to improve your sound situation, hopefully without requiring that everything be thrown out.
Marlayna Glynn Brown is the director of business development for Dickensheets Design Associates, www.dickensheets.com, in Austin, Texas.