Top 5 Acoustical Issues for Churches

You can have the best sound system in the world, but it won’t matter if you don’t address these issues.

Through awe-inspiring architecture, transcendent musical moments, congregational singing, thoughtful sermons, and times of introspection and prayer, churches strive to share the message and hope of the good news, positively impacting the lives of the individuals gathered there for worship. The single most important purpose for any worship service is to unite the congregation in worship, and communicate the message.

But what if a skillfully played praise song isn’t moving people because they are focused on how harsh or loud the PA sounds in the space? What if the congregation can’t understand the words of the sermon due to excessive echo? In many churches, the acoustical environment can be the difference between someone receiving the message or leaving unfulfilled.

Even with the world’s best sound system, the quality of sound will be limited by the physical space in which the system is being used. Room acoustics can either help or hinder—either assist you with communicating the message or act as an obstacle.

Here are the top five acoustical issues that affect the performance of a worship space and, more importantly, ways they can be solved. By addressing some or all of these problems, you can ensure your church’s message is being communicated effectively.

1. Excessive Reverberation

Reverberation Time (RT) is defined as the amount of time (expressed in seconds) that it takes for sound to decay by 60 decibels (dB). Typically, having a long RT, on the order of 2.55 or more seconds, will result in music lacking clarity and speech being difficult to understand. Think of big cathedrals, which may have RT in the 6- or 7-second range, which sound amazing for choral music or organ, but are very difficult when it comes to intelligibility of speech. For speech applications, the target RT is typically shorter than what would be best for music applications. Since most worship services blend both speech and music, it is important to select a target RT that both improves speech intelligibility and aids the worship experience through song.

RT is frequency dependent. The size/shape of the room and the surface materials involved (carpet vs. tile, concrete vs. drywall, padded chairs vs. wooden pews, etc.) all have a dramatic impact on the RT across the frequency spectrum. In some rooms, the low-frequency RT might fall between 2–4 seconds, while the mid-/high-frequency RT could be in the 1–2-second range. This imbalance can cause a room to sound too “boomy” or “muddy” and make it difficult to communicate effectively.

Solution: Proper selection of absorptive, reflective, and diffuse surfaces in a room will help to bring the RT to an acceptable level. Attractive, fabric‐covered fiberglass panels that visually blend into the walls will help absorb acoustic energy and will bring the RT down, while diffusion elements scatter sound to reduce harsh reflections and retain some liveliness in the room. A common approach is to absorb energy that is reflecting off the rear wall and to scatter or diffuse lateral reflections from side walls. The thicker the absorption panels, the more effective they will be in the lower-frequency range.

At a minimum, 2″-thick panels should be used, but some rooms require additional low-frequency absorption, where 4″ panels and barrel diffusers are needed. The more absorption added, the more controlled or “dry” the room will sound. Be careful not to add too much absorption, because speech intelligibility could actually get worse in some areas, and the congregation could be less likely to participate in singing due to the fear that everyone around them will hear their voice. For best results, it is recommended that churches consult with a professional before purchasing acoustical treatment to ensure the correct materials are used and that they are placed in the most effective locations.

2. Slapback or Flutter Echo

Distinct echoes can be a distraction for the congregation as well as for those presenting on stage. Humans perceive the original signal plus the reflected energy (called early reflections) that arrives within approximately 70 milliseconds (70/1,000ths of a second) of the direct sound, instrument, or voice as the same sound. We are not able to differentiate a reflection that happens rapidly after the direct sound—we just think that is what the source sounds like.

When a reflection arrives at your ear more than 70 milliseconds later, the brain hears that reflection as a separate sound source. If the rear wall or balcony face is left untreated, these reflections, known as slapback echo, can often be heard while clapping, speaking, or hitting a snare drum on the stage. Since sound travels at 1130 feet/second, if the rear wall or balcony face is more than 30 feet away, you are likely to hear distracting echoes reflecting from the back of the room.

Flutter echo is defined as a rapid series of echoes originating between two parallel surfaces. You may have heard this before if you have stood between two parallel, reflective surfaces and clapped your hands. It sounds similar to a ping-pong ball bouncing back and forth. This type of echo can be very distracting.

Solution: Slapback echoes are normally addressed by adding absorption material to the offending surfaces—typically the rear wall and balcony front—which directly face the front of the stage. Flutter echoes can be handled with absorption or diffusion that can be chosen depending on the impact the selected acoustical material will have on the overall RT of the room. If you are in the process of building a new facility, choosing a fan‐shaped room design (where the room is wider at the rear of the room than at the front) will help reduce flutter if the side walls are angled at least 6 degrees each.

3. Stage Volume/Resonance

When a musical band is added to a worship service, the noise from the instruments onstage can be problematic if not controlled properly. Sound sources can reflect off the stage walls, ceiling, and floor and bounce back into the congregation. This can result in the sound being too loud or harsh and can cause issues for the sound engineer as the stage noise fights with the PA system.

Stages are often built so that the area below the stage is hollow. Guitar amplifiers, drum kits, subwoofers, and other vibration sources can vibrate the stage and cause a resonance that can enhance certain frequencies. This hollow, resonating cavity is essentially like having another kick drum in your system that doesn’t have a fader assigned to it, so you cannot turn it down. A loud and resonant stage can also make it difficult for musicians to hear their instruments clearly, which can lead them to want to turn up or play harder.

Solution: Moving toward a quiet stage concept (using in‐ear monitors, drum shields, electronic drums, etc.) is a way to reduce stage volume and is highly recommended. If a quiet stage is simply not in the cards, it would be beneficial to use absorption panels to reduce reflections from the front and wing walls of the stage. The stage resonance issue can be tackled in a few ways. Adding insulation material inside of the hollow cavity will limit the ability for it to resonate. It is similar to adding a pillow inside of a kick drum. Another step you can take is to cut out vibrations at the source by decoupling amps, subwoofers, and drum kits. Isolation platforms placed underneath these vibration sources act like shock absorbers to limit the amount of energy that gets into the hollow stage.

4. Frequency Imbalance

Some rooms may reflect lots of low-frequency energy while absorbing high-frequency content, resulting in a bass‐heavy, muffled sound. In other rooms, the low-frequency range may be thin and lacking while the high-frequency energy seems too loud. Some of this is dependent on the sound system, but the room itself plays a big role in how balanced the sound is.

For example, a room that has concrete walls, a carpeted floor, and a drop‐tile acoustical ceiling will seem unbalanced because concrete doesn’t flex with low-frequency waves. Combine this with the fact that carpet and ceiling tiles absorb mostly high-frequency energy with little effect on low frequencies, and you have the perfect recipe for an unbalanced room that struggles with speech intelligibility and musical clarity. Swap out the concrete walls in this scenario for standard drywall, and now this room performs in a vastly different way.

Solution: Choosing surface materials that absorb sound energy evenly is crucial in the design phase of a room. For existing spaces, using the correct amount and distribution of absorption and diffusion panels can help to bring the room back into balance. For the room mentioned above, it would make matters worse to add 1″-thick absorption panels to the room, because that would increase the high-frequency absorption without affecting the low frequencies. A combination of thick absorption panels and barrel diffusers (which scatter high frequencies while absorbing low end) can boost low-frequency absorption, and some of the ceiling tiles could be swapped out for diffusion to bring life back to the room.

5. Sound Isolation

Exterior noises such as traffic, sirens, airplanes, weather, etc., can distract the congregation and take their focus away from the message. The noise isn’t always coming from outside the building. Nearby nurseries, bathrooms, and common areas can also contribute to the problem.

Solution: Sound isolation is difficult to address after a building is constructed, because the solution often requires construction (adding mass and decoupling). If you are building a new facility, it is important for the walls, ceiling, and floor of noise-sensitive rooms to be properly designed to mitigate noise. If you are selecting a location for a new building, spend some time to understand potential noise sources that are nearby. Are there active train tracks close by? Is this property in the flight path for a major airport? Location is everything when it comes to isolation. Another thing to consider when planning a space is the location of noise-sensitive rooms in relation to each other. Having air locks or vestibules between common areas and the worship space can minimize noise leakage when someone enters or exits the room. Try to place the nursery or youth rooms on the other side of the building.

Addressing the acoustical issues in your worship space can seem like a daunting task, but there are professionals who are willing to help and tools that are cost effective and aesthetically pleasing. Clear, intelligible sound is possible with the right plan and execution. Once these acoustical issues are solved, it will be much easier to communicate the message.

This article first ran on Sweetwater.com. Used by permission.