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Last week Lee sent in a question about acoustic treatment in church situations. He asked “What measurements do I need to take? What’s the critical information you need in order to help us with an acoustic design church solution?” Okay with churches you have two issues. One, you have to have speech intelligibility because the church’s product, so to speak, is the spoken word. What is the other churches product? The other churches product is music. There is usually always some kind of music live through the PA or choir. So we have speech and music.

So we have to be able to hear the spoken word and then, when the choir comes in, to provide emphasis for the spoken word. So we have speech and music that we have to get right in one room and that’s really hard.

Speech intelligibility and music in one room

If you look at the graphs you get a tiny amount of space on the graph to hit your target reverberation times and other variables. It’s not easy. We forget about the speech in the beginning and just try to get the room down to a point where music sounds good and then we work on speech later.

Music is all about lowering the reverberation times. We’re in churches that have 4, 5, 6 second reverb times even at low frequencies whereas the ideal is one and a half. So we’re four times out of ideal, each one hundred percent increase from ideal costs money and materials and square footage within the church to resolve and this is always the trade-off in the church.

How do you get the most treatment in there that costs the least amount of money and has the largest impact?

You have to satisfy those three variables. So we have a program with our churches where we supply the analysis, spec the units out and we have church members build them. It’s a wonderful system because labor is the most expensive part of any acoustical build. The materials are not that expensive compared to labor but when you need a lot of them they can get expensive. So we spec-in all the materials, we get them in our economy of scale prices here locally in the Phoenix area and then we meet with the church members and we have our plans, our drawings and then we meet with the woodworkers within the congregation who are going to build the product.

They build it under our supervision and install it. It also saves the church a lot of money as they just end up with material costs and a small design fee from us. So it’s a nice process that works.

Reverberation times are the key thing that you have to look at

So if you’re asking for a measurement, a single measurement that will tell a lot of the issues then look for the reverb time. To measure for reverb time and frequencies, send me the information and I’ll put it in our database and compare your numbers to ours and advise from there. We’ve got a lot of churches in there. I can save you time, I can save you money as I’ve already done the building you’re doing so let’s use the date for all our benefits.

What do they use to measure the reverberation time, what tools?

Well you have to have a driver or a speaker that’s capable of producing 80 to 85 dB of energy, dB SPL of energy within the room and you have to have a measurement microphone and the appropriate software. For the reverberation time you can download free software, for that.

Wizard probably is the cheap software that was designed by a British engineer, he just gives it away, it’s incredible stuff. You’ll need a measurement microphone, I’m sure he could suggest the measurement microphone that’s compatible with his software. Always stick with the engineer who designed the software’s recommendation he knows the software inside and out.

So if the designer of Wizard says ‘buy this microphone’ then buy it, don’t try to shortchange it. It’ll be a hundred bucks at the most anyway. You’ll also need a laptop but that’s it and then you know, if you get that equipment and then you get the room, call me and I’ll tell you where to do the test. I’ll tell you where to locate everything so you get the best results.

In Summary

If you would like your room acoustic issues analysed for free by me then please fill in the form here and I will be happy to take a look for you.


Dennis Foley

I am an acoustic engineer with over 30 years’ experience in the business. My technology has been used in Electric Lady Land Studios, Sony Music of New York, Cello Music and Films founded by Mark Levinson, and Saltmines Studios in Mesa, Arizona, along with hundreds of others.

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