Compound Noise Issues in Sanctuaries
By: Aimee Sanford
Worship facilities are among the most common to seek out acoustical advice and treatment. This is because the goal of a worship service is to spread the word and create fellowship – usually with sermons and music.
If the sermon is unintelligible, if musical detail is lost in reverberation, or if there is distracting peripheral noise, the congregation will likely not be engaged, educated, or even enjoy the service.
Proper consideration of the architectural acoustics in a sanctuary can ensure delivery of the message and result in a delighted, inspired fellowship – prepared to go out and encourage others to join them at the next service.
The key to begin addressing the acoustics in your sanctuary is to identify the noise issue and its source. Not all acoustical problems manifest from the same architectural component, and solutions differ in product material and placement.
For example, Church of Christ at Mountain View in Winchester, Virginia, had an issue with background noise, sound intensity, and intelligibility. This was not, however, a cut-and-dry case of “you need more soft vs. hard surfaces surrounding the seating area.”
Sure, the hard surfaces surrounding the pews in the sanctuary caused some reverberation, which can muddle the audio from the speakers, but Tom Stephenson, a congregation member and mechanical engineer, who also happens to run sound for the church, knew this would not solve all of CCMV’s acoustical issues.
After a remodel of the auditorium a few years back, the sanctuary’s newly painted block walls created a long RT60, or reverberation time.
RT60 is the amount of time it takes for sound from a single source to “die” or finish reverberating so that it can no longer be heard. The longer the reverberation time, the less detail you can distinguish in sounds and the faster a little bit of noise can turn into an uncomfortable amount of noise – drowning out speech and music.
In addition, CCMV’s two projector rooms, located to the upper left and right sides of the stage are cube-shaped, with one open wall in each, facing the sanctuary seating area. The motor noise from the two projectors was reverberating around their cubed-shaped enclosures and being amplified before shooting out the openings into the large worship hall.
This resulted in the projectors being highly audible to seated guests, creating a noticeable change in ambient noise when the projectors were powered on and off. This was particularly bothersome at formal events like weddings when the AV system was being used to present a slideshow or create other audiovisual effects.
“When had programs or weddings in the auditorium and people wanted to show something on the projectors, we would have to keep them running throughout the service even when we weren't using them,” said Stephenson. “If we turned them off, it would get suddenly silent in comparison, because you can hear the projector fans so loudly in the auditorium."
Lastly, the cubic enclosures acted as amplifiers for any sound that entered them, as well, reflecting sound back out and creating “slapback” echoes.
This noise issue is different from traditional reverberation and is characterized by high frequency sounds that bounce between parallel surfaces or very open areas, creating clear, intense echoes of the original sound.
First, AlphaSorb Acoustical Panels were installed along the lower level, balcony facing, and second level to absorb sound and lessen reverberation from audio, sermons, and congregation chatter.
These fabric-wrapped fiberglass panels were named a Hot Product of 2008 by Religious Product News, are Class 1 Fire Rated, and come standard in any color Guilford of Maine FR701 acoustical fabric and in custom sizes up to 4' x 10' in 1" or 2" thicknesses. The 2” versions have NRC ratings of up to 1.15.
NRC stands for Noise Reduction Coefficient and is the most commonly used rating for sound absorbing treatment. The higher the NRC, the more sound a material absorbs when a wave reaches it. NRC ratings of 1.00 and higher mean the material absorbs all sound that comes into contact with it, thereby eliminating the possibility of reverberation off that surface.
While this treatment increased intelligibility in the auditorium, it did not eliminate the distracting noise emitting form the projector rooms.
To address this issue, treatment needed to be applied at the source. PolyPhon Polyester Acoustical Panels were installed on the three walls inside each of the two large projection rooms.
These polyester panels are a popular environmentally friendly option that are made from 100% polyester (60% PET-recycled fiber and 40% PET-virgin fiber) and are 100% recyclable. The 1” thick PolyPhon Panels have an NRC value of .75, meaning they would absorb 75% of the projector motor noise reflecting around the two rooms.
Polyester panels offer many environmental advantages over the traditional fiberglass sound absorption panel, such as:
• Formaldehyde free
This treatment prevented the buildup of motor noise before it even reached the congregation and ended the persistent slap-back echo.
Also, the panels in the projection room have made it possible to power the projectors on and off during services with no sound change in the auditorium.
The reverberation time was decreased by over a full second, and Stephenson was thrilled that some congregation members who used to use the church's hearing assistance Systems no longer require them.
Aimee Sanford is communications specialist with Acoustical Solutions Inc., based in Richmond, Virginia, www.AcousticalSolutions.com.