Basic acoustical knowledge lets you interact with the consultant, sound contractor and Architect to assure that the acoustical requirements of your worship space are satisfied.
The worship space has clearly evolved over the ages from the intimate synagogues predating the dawn of Christianity to the grandiose edifices of the medieval cathedrals, to present day Protestant, evangelical and electronic ministries, which utilize acoustic / electronic contemporary music, dynamic preaching and the audio/video media.
Each of these worship spaces requires quite different architectural acoustics. Most notable is the difference between the short reverberation times in spaces stressing speech intelligibility and the long reverberation times in spaces where music is fundamental to the service.
Acoustic Needs Have Changed
While acoustic instruments like the pipe organ and piano are still in use, new electronic organs, synthesizers and other contemporary musical instruments have become more and more commonplace in worship services.
These changes pose acoustic challenges. While the highly reverberant acoustics of the cathedral were well suited to the organ and Gregorian chants, many modern day parallel sided, flat-walled worship spaces cannot satisfy the requirements for speech intelligibility and music performance without appropriate acoustical treatment.
Congregation Needs Have Changed
In addition to changing musical sources d performance requirements, the nature and size of the congregation has changed. Many modern worship spaces have incorporated aspects of the sound stage, video and audio recording studio, theatre, and concert hall. Fusing all of these new techniques into the worship space is a formidable task.
The modern day worship service involves the active participation of the pastor, the performing musical group, and the congregation. 'Each Participant experiences a unique set of problems.
You may have difficulty in hearing yourself preach due to inadequate acoustic reinforcement or monitor system. Or conversely, strong acoustic reflections from your monitors could cause squealing feedback.
A poor acoustical environment makes it difficult for choir or band members to hear themselves and other performers, leading to pitch problems and a poor sense of ensemble. It may be a problem for the choir to synchronize with the organ or other musical accompaniment. This is usually caused by time delay problems resulting from poor positioning of the performers and/or disproportionate sound levels.
Poor intelligibility of your presentation may be caused by slap echoes of the sound system reflecting off the rear wall of the sanctuary. This is usually aggravated by a focusing or curved rear wall. Poor sound projection into the sanctuary results in an inadequate musical support level which discourages congregational participation.
The solution to these problems requires electronic modification of the sound reinforcement system and acoustical modification of the materials covering the walls, floor and ceiling. When someone mentions the term "acoustical material", unfortunately, most of us think of sound absorbing substances. These materials absorb or attenuate sound by converting the acoustical energy into heat. But consider other forms of acoustic modification.
The walls, ceiling and floor in your worship space are flat or curved surfaces that offer a second type of sound modification called reflection.
Reflective surfaces essentially redirect sound and offer little absorption. They operate on a principle similar to that which occurs when a billiard ball bounces off a cushion. You may remember this principle from high school physics-the angle of incidence equals the angle of reflection. This type of sound scattering is called specular reflection. Since there is very little absorption the reflected energy is comparable to the incident sound.
If the scattering surfaces are concave or curved, the sound can actually be intensified or focused at certain positions in the room.
Now for the last ingredient. Imagine the intricate interiors of a cathedral or concert hall. These environments are appointed with statuary, parapets, chandeliers, and protuberances of every size and shape. These surfaces do not absorb or reflect sound, but rather diffuse or distribute sound. They scatter sound arriving from any direction in many directions instead of just the specular direction.
But, because of increasing building costs and seating requirements, flat concrete, dry wall or cinder block surfaces have become all too commonplace. The result is poor acoustics and an ineffective worship space.
Is there a modern method to distribute the music and spread "the word"? The answer is yes.
When a surface is configured to contain a series of depth variations based on certain number theory sequences, they scatter sound uniformly in all directions.
This is a constructive way to control reflections because sound is not absorbed or removed from the space, it is merely uniformly redistributed.
It is very important for you and your musical director to be aware of these acoustical fundamentals to intelligently discuss your needs with sound contractors, acoustical consultants and architects.
In this first part of this continuing article, I have identified some of the acoustical problems facing modern worship spaces. I have briefly described the general characteristics of absorptive, diffusive and reflective surfaces available to solve these problems.
In the next article we will examine specific properties of acoustical materials and begin discussing how these surfaces are used and ,abused.
Dr. Peter D’Antonio is an Acoustical Engineer with RPG Diffusor Systems Inc. Largo MD.
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