Here we present a portion of a chapter in the book “Sound of Worship” by Douglas R. Jones, published by Focal Press.
Noise is a problem that every church must deal with regardless of its worship style or form.
Noise is basically unwanted sound. It is important to realize that the definition of noise includes a subjective component. Noise is unwanted sound.
Noise can be any sound that intrudes on someone’s space. It can be sound that in another context may be deemed desirable.
Noise can originate outside a structure or from within. It can be a by-product of the congregation itself.
In any case, in all styles of worship we looked at in the previous section, unwanted sound will always be viewed as a hindrance.
Unlike other aspects of acoustics, noise control or abatement is very difficult and expensive to achieve after a building is built. If noise control is built into the structure or design it will not be nearly as costly.
There are two ways that noise, or any sound for that matter, gets into and propagates through a space. Unlike light, sound must have a medium for it to propagate. Sound will travel from its source through the air or through a structure, often both. Both airborne and structure-borne sound are easy to control in theory, but in practice both can be quite challenging, as every possible path must be accounted for.
With airborne sound, we must achieve virtually airtight conditions if we are to achieve isolation. Structure-borne sound requires mechanical decoupling of the source from the structure.
Consider the following scenario. The First Baptist Church is planning a new building. The design calls for a nursery to be built, as they often are in Evangelical churches, right off the back of the sanctuary. The worshippers in the sanctuary do not want to hear the infants crying—fussing babies would be considered noise to all present with the possible exception of the parents!
However, caregivers don’t want to miss the entire service, so a window is installed in the wall between the sanctuary and the nursery so the caregivers can observe the service and hear by means of a loudspeaker system installed in the nursery. After the dust settles from the construction, and services are held in the new church, a problem emerges.
The worshippers sitting in the back four rows can clearly hear the babies crying as well as the caregivers carrying on conversations in the nursery. The architect is stymied. The walls are appropriately filled with fiberglass insulation and the window was one of those fancy sound-proof ones. How could the noise be getting into the sanctuary? An investigation revealed three paths that sound could take.
One was around the glass. If a window is not fully sealed into the frame it will not stop airborne sound. The contractor had not been careful enough with the installation, figuring the trim would cover the gaps around the window.
The second path was under the wall plate. The plate was not sealed to the floor and the drywall was cut shy of the floor, leaving an eighth of an inch gap, covered, of course, by the baseboard. Vinyl baseboard does a good job of concealing gaps, but those gaps are all potential air leaks, and therefore sound leaks.
The third offending path was an electrical outlet placed in the common wall between the nursery and sanctuary.The electrician had used back-to-back electrical boxes to feed both rooms from one drop, resulting in a significant hole right through the wall.
It is very important to note that fixing any one of these flanking paths may result in virtually no improvement. Fixing any two might yield a minor improvement. All flanking paths must be found and sealed if airborne sound is to be controlled.
Other common paths for airborne sound include traveling over a demising wall that is not sealed to the deck, sound leaking through penetrations through walls (or floors or ceilings), for example penetrations to allow for sprinkler systems. HVAC ducts are often the biggest culprits. They can be very effective speaking tubes! Noise can also intrude into a space through the structure. Sound in the form of vibration will travel very efficiently through solids.
The speed of sound in air is approximately 334 meters per second (m/s) (1130 feet per second (ft/s)). The speed of sound in common building materials such as gypsum board is on the order of 3000 m/s.
The good news is that for acoustical sources of sound, the transfer of energy from air to structure is very inefficient. A crying baby is not likely to create enough acoustic energy for the sound to travel throughout the structure and cause a problem.
However, a simple box fan sitting on a wood floor can often be heard in the apartment below as the vibration is transmitted directly through the feet of the fan to the floor. Once the vibration is in the wood of the floor it will travel to the joists and then on to whatever is attached to the joists and ultimately to the whole structure. This is a much more efficient transfer of energy than is possible through the air. We only have to lift the fan off the floor by an inch or so to prove this.
Controlling structure-borne noise can require careful engineering and be a real challenge. We must either isolate the source from the structure, or isolate the “ receiving room ” from the structure. It is most often better to consider isolating the source rather than the receiver.
In the case of a church, it would be silly to acoustically float a sanctuary from the structure of the building to get rid of HVAC noise. Isolating the offending HVAC equipment is much more practical. If we were building a recording studio in a building situated in an urban area where the structure of the building was rife with vibration from all sorts of sources ranging from traffic to HVAC to elevators, the only practical solution may very well be to isolate the entire studio by building the room on isolators.