The way we describe it is, an average audio system in a good room will work well, but a great audio system in a bad room will work terribly, all because of the physics involved.
We've all been to one.
Maybe you are even the pastor of one.
That church where people constantly complain about the sound system.
“I can't hear. It hurts my ears; It's not loud enough. It's too loud”—with both complaints often from the same service.
If you can relate to the above, then I'm sure you're tired of it. You may have gone as far as replacing the sound systemonly to receive the same complaints.
There's a good chance that your problem has little to do with your sound system. That's because what most people normally think of as their sound system is actually only half of their sound system.
The other half of the system is the room itself.
Unlike lighting and video, your sanctuary or auditorium plays a major part in the sound that reaches your congregation's ears. This aspect of the room is what's referred to as acoustics. And acoustics is one of the first things that gets removed from consideration when pricing out a building project. Unfortunately for those churches, they've also thrown-out the-consideration affecting half of their sound system as well.
So what types of problems might you experience in a room that has acoustics issues?
"Unintelligibly is the biggest problem people experience," states Brandon Pendley of Pendley Productions based in the greater Atlanta, GA area. "When sound starts bouncing off of walls, it creates long reverberation times and slap echoes. These make the spoken word especially hard to understand."
"Some churches think, we’ll just get a louder system," adds Colleran. "But the room is too reverberant to make out the words. So they buy another system, and have the same problem because the problem isn't the audio system, it's the acoustics of the room."
"The way we describe it is, an average audio system in a good room will work well, but a great audio system in a bad room will work terribly, all because of the physics involved," states Nick Colleran of Acoustics First, based in Richmond, VA. "And physics always wins."
More issues that occur with a room's acoustics include hot spots and dead spotslocations where certain frequencies are much louder, often resulting in shrill or painful tones.
"Hard surfaces like walls cause sound to bounce around the room, and when the sound bouncing off the walls and other surfaces meet up with the sound from the loudspeakers, this creates hot spots and dead spots," explains Colleran.
Additionally, bass often tends to build up near walls and especially near the corners of rooms. These are referred to as reinforcement spots. Dead zones can also occur in low-end frequencies, like bass guitar and kick drum. This is where the sound bouncing off the walls meets up with the direct sound from the PA system, but it's completely out of phase, and cancels that frequency out.
Marty Atias of ATS Communications shares one of his experiences. "In this particular church, the audio console happens to be placed in a reinforcement spot for bass. The bass sounds very loud when I'm at the console.
But when I step away, the bass isn’t that loud.
In some places you can’t hear it at allthe direct sound gets cancelled from the reflections. I’ll pump a low frequency sine wave, say 100Hz through the P.A. and walk around. It can be heard really loud in one seat, but three seats away it can barely be detected. These nodes' can be anywhere in the room. Move it up to 125Hz, and different seats are affected.
For the mix position, that’s a problem because I can’t trust what I’m hearing."
Colleran notes, "Cancellations will happen the same way at any volume. The sound tech may try to get the bass louder at those locations by turning it up, but that will have no effect. Instead of turning up the volume you need to add diffusion or absorption materials to the walls to reduce the reflections that are causing the problem."
One more problem is slap echoes that bounce off the back wall and come back to the stage. "If you’re getting an echo off the back wall," says Colleran, "the musicians and choir can’t keep time. Musicians might turn up their monitors too loud to drown it out."
"Additionally," adds Atias, "these echoes, and the louder monitors they encourage, will increase the chance of feedback and ringing from your microphones."
As you can see, acoustics issues can cause a lot of problems with the sound your congregation experiences. When a room has problems like this, it's frustrating for the congregation and can reduce your ability to retain congregants.
"It can be painful to sit in a service and try to listen," states Pendley. "It’s fatiguing and uncomfortable. People disengage. Or they just stop attending altogether. When there are a lot of echoes or reflections going on in the room, you can't concentrate on the message."
Are you wondering if perhaps some of the complaints you get are acoustics related? Try this little experiment that Colleran describes. Blow up a balloon and pop it. You’ll hear the reflections and echoes that impact the ability for people to hear the sound from the PA system. "No sound system can effectively lower the reverb time or echoes," says Colleran.
Many churches waste a lot of resources on trying to address acoustics issues via their sound system. "However, if you get the acoustics right," states Colleran, "you’ll have money left over for a better sound system."
Reverberation: The sound created in a space with hard surfaces where a sound persists for some amount of time after the actual sound source has stopped. This is a very pleasing effect (and often artificially added in) to music; it tends to make the spoken word very difficult to understand, especially if the reverb time is long.
RT60: When an acoustician discussed the reverb time in a room, they refer to it as RT60 time. This is the amount of time it takes reverberant sound to drop to 60 decibels below the original sound source.
Slap Echo: This is a distinct single echo, not a reverberation, of a sound source, usually caused by the sound bouncing back from a wall or other hard surface of a room.
Phase Interference: A change in tonal qualities of a sound when the original sound is merges with that sound after it bounces off a surface. When the bounce is completely "in phase" with the original sound, it doubles the perceived volume of that sound. When it is completely out of phase, it cancels out the sound and you hear nothing. The phase interference at any given location varies based on frequency. At any given seat, one frequency may be completely in phase; another can be completely out of phase.
Bass Build Up: The effect that usually happens at walls and corners where bass frequencies bounces off the walls and joins the original signal in phase, causing the bass to sound two to three times louder than it really is.