This issue of FRONT of HOUSE is focused around the house of worship market, an area where I have a large amount of personal experience. From volunteering at my own small church, to being a hired gun in large mega churches, the majority of my hours logged behind a mixing console have been in the church setting. As a result, I have direct experience in this area, which may make this article rather contrarian to what is usually composed regarding church sound.
This article examines the issue of intelligibility, a topic that comes around every time the house of worship market is in focus. The typical article on intelligibility in a trade magazine is summed up in the following manner, “use directional (i.e., large) loudspeakers, and aim them directly at the audience to minimize room reflections.” While this advice may be firmly grounded in physics, it is hardly practical in the real world of church sound. While mega churches end up in the magazine, the vast majority of churches are smaller, and many are extremely visually sensitive to a “flying junkyard” of large boxes above their stage. Big directional speakers are often not viable in real house of worship environments, and articles that espouse them as the preferred course of action are a disservice to pro audio practitioners looking to grow into the church market.
Churches Don’t Care
Another truth from the trenches is that churches do not care about intelligibility. Or rather they may think that they care about understanding the words in speech and music, but the majority of their sonic decisions are driven by aesthetic, musical, or other sensibilities. I have never been hired to “make the pastor sound clearer,” but have come in many a time to mix music when the church volunteers got in over their heads. Similarly, while I have used the speech transmission index (STI) to put numbers to a problem, I have not been able to sell it pre-emptively as a number that matters during the course of design.
So what then? Are churches doomed to forever have muddy, unintelligible singing and speaking? I think the answer to this question is a resounding “no.” First, the recent trend in church environments is towards smaller, more intimate spaces. Large churches are increasingly developing multiple smaller campuses as an alternative to a single large “mother ship.” All things being equal, these smaller rooms will naturally have denser and shorter decay profiles. This decay characteristic tends to promote the clarity of speech and intimacy of congregational singing.
Further, most new church spaces that I have been around share more in common with performing arts centers than any other type of structure. The owners of these spaces are more tolerant of using soft goods to break up problem reflections. The best acoustic designs even highlight these elements in a visually appealing manner to make them part of the space’s architectural motif. Next, the available acoustic treatments have never been better. Products like ICC’s K-13 spray treatment, Owens-Corning SelectSound blankets or MBI Lapendary panels bring new flexibility acoustically and visually to bring rooms back in line. Finally, the available pattern control from digitally steered column speakers has improved the capabilities of directional control in a tall, thin form factor.
The Basics
Fundamental to intelligibility is the concept of masking, which I discussed more extensively in last month’s column. Masking, summarized briefly, is the brain’s ability to discern certain sounds in the presence of other sounds. Fundamental to masking is the concept of signal to noise ratio. In the presence of broadband noise, how much louder must a certain signal be before it can be understood clearly over the noise that exists? Noise can have far reaching sources. It can be the sound of the crowd, the fans in a dimmer rack, the rumbling of the HVAC system, or the notes played by the band obscuring a vocal melody line.
While there are numerous subtleties in determining intelligibility, in broad strokes human speech is obscured by the presence of too much outside information (noise) in the bands between 150 Hz to 600 Hz, and 2 kHz to 4 kHz. If you have too much unwanted sound (or not enough wanted sound) in these ranges, problems will occur. This rule of thumb will guide the rest of our discussion.
Win the Easy Battles First
The typical church technician is just like everyone else in pro audio, they want their mixes to be clear and compelling, they need to keep their bosses happy, and they like fancy new gear just as much as anyone else. They need their congregation to understand both speech and music, while keeping complaints to a minimum. Whether you are the church tech or an outside integrator, sometimes the social proof of helping attack small, inexpensive issues gains the church’s trust when considering larger projects.
A basic win achievable in most church environments is facilitating improved microphone technique. Improved microphone technique is helpful from three standpoints. First, it improves the potential acoustic gain (PAG) available to the sound system. This allows the operator to boost the overall level of the speech signal from the sound system before the onset of feedback. This increased level improves the signal to noise ratio of the speech against the background ambient noise.
Second, improving microphone technique insures that the vocal presenter is closer to the microphone, and here the inverse square law becomes your friend. Since the ambient noise sources are far away from the microphone relative to the vocalist, the amount of ambient noise picked up by the microphone falls off in proportion to the amount the vocalist is picked up. This means that the signal being fed to the sound system contains proportionately less re-amplified noise, and more of the desired speech or singing.
Finally, the improved microphone technique usually serves to favorably increase the balance of consonant (high frequency) sounds to vowels (lower frequency) that the microphone picks up. Generally this increased high frequency energy at the microphone from the vocalist will improve intelligibility.
Improving microphone technique has taken several different forms for me over the years. It has been a simple admonition towards the singer(s) to “leave lipstick on the grill.” Other times it has been re-ordering the location of musicians on stage to provide separation between loud sources and quiet singers. In another case, it was showing a presenter (who liked to use a handheld microphone) video playback that showed how they unconsciously let the microphone drift down to waist level over the course of speaking. It has been convincing clergy to switch from a podium microphone to a lavaliere, or headset microphone.
One particularly witty pastor who I worked with regularly said that switching to a headset from lavaliere made him feel like a pop star, and he would hum a couple bars of “Papa Don’t Preach” for sound check the first few weeks on the new headset. Thankfully he also listened to recordings of his sermons, and never second-guessed the headset microphone upon hearing how much clearer the recordings became.
The cost of improving microphone technique can range from “free” to “reasonable,” depending on the existing equipment and state of proper use. Related improvements focused on improving the source sound include coaching speakers to annunciate, tweaking a singer’s monitor mix, or providing a confidence monitor to help a presenter feel more comfortable on stage.
System level Improvements
Moving beyond microphone technique, there are multiple system level approaches that can be used to improve intelligibility. Tearing out the existing sound system and replacing it with a new, high directivity replacement is the sledgehammer technique, so let me instead suggest some more subtle approaches:
Re-aim the existing sound system: I have never ceased to be amazed at the diversity of incorrect aiming approaches in installed systems, even among systems which having aiming tools available. A discussion on aiming is an entire article (or three), but ignoring the complications in execution, it remains an extremely effective course of action.
Add fill systems: Is the main system being asked to do too much at either the front or the back of the room? High frequencies muddy at the back, or mid-bass of the main system bleeding all over the stage? Ask the main system to do less! Aim it to cover the majority of the room, and supplement it with smaller, quieter, more affordable fill systems at the extremities.
Measure the system at the lectern — The interactions of multiple speakers in clusters cause a myriad of side lobes that appear far off the primary axis of coverage. As a system commissioner, I place a measurement microphone at the location of the speaker (or lead vocalist) to make sure that the processing applied to the array doesn’t cause troublesome lobes to appear at this location. In the absence of multiple speakers in a cluster, looking for lobes from individual speakers at the lectern is still a good idea to provide a baseline for equalization.
In many churches, the existing installed system components are completely adequate, as long as you don’t expect them to hang the moon. I have been amazed at what replacing tired diaphragms, re-aiming, and adding some fills can accomplish to freshen up the music reproduction and improve the clarity of speech. These kinds of upgrades can be more easily completed on the Sunday to Sunday (or Thursday rehearsal) typical of most active churches.
Churches have become gun shy of pro audio companies in part because so many have heard a sales rep tell them, “you can’t possibly have good performance with what you have now, it needs replaced with [pet product] to make things great.” Supplementing, rather than swapping, might be just the necessary angle to close an upgrade and subsequent service contract for your firm.
Blank Sheet Scenarios
Of course supplementing or freshening the existing system isn’t always the best approach. Sometimes the existing system is decrepit, contains components that are broken and/or can no longer be serviced, was wrong for the application, or the client wants to start anew. During the extended era when many churches switched from more liturgical music and instrumentation to a more modern collection of instruments, starting from scratch was extremely common and often prudent. So, if one is going to start from scratch, either with the system or the room, how should the professional approach this to insure maximum intelligibility?
One overlooked area, and personal pet peeve, is the relative level of background noise inherent in church spaces. This noise is normally dominated by the HVAC system in modern buildings. The acoustics textbooks suggest a background noise level of around NC30 for house of worship spaces, but I have been in spaces that were NC60. The incessant background rumble from corners cut in the HVAC system hurts intelligibility every single week. The life of an acoustician can look more like that of a mechanical engineer designing air handling systems than anything familiar to those in pro audio. Poorly designed HVAC systems also contribute substantially to the operating budget of churches, both in cost of energy to run and in heat losses through the installed components. Over time, I have had the luxury to work in two rooms that were extremely quiet and the difference is pronounced. And of course a quiet room is also good at keeping the sound from leaking out to adjacent properties during services.
Another practical suggestion is to not hang speaker clusters directly over locations critical for speaking or singing. If you are not skilled in measuring for side lobes and do not have vocabulary to address them within the array using processing, it is best to avoid the potential problem spots. Often it is easier to move the lectern or vocal microphone position, of course.
A related suggestion is to be aware of the effect that prosceniums, balcony lips, and catwalks can have on the acoustic environment. These apparently small architectural features can be devastatingly effective in creating strong discrete reflections that wreak havoc with intelligibility on stage and in the audience. Judicious application of a product like the K-13 spray-on cellulose acoustical treatment on the exterior of these features can reap big gains in knocking down strong discrete reflections that make processing speech difficult.
Final Words
One thing that I hope to convey to the readers of FOH is that you do not necessarily need to hang giant speakers, or cover the walls with acoustic paneling, to gain intelligibility in the church environment. Certainly these approaches have been used, but often as a matter of last resort in environments where pre-emptive approaches might have prevented such more drastic measures. A holistic approach that addresses sources, microphones, speakers, acoustics, and ambient noise will combine to make sure that word and song is heard clear and crisp.
