Is It Loud Enough!!!


What is a Good Listening Sound Level for Speech in a Church?


From the JdB Church Sound Series


Recently I read a recommendation on the web for a loudness level for speech in a church. The suggestion was between 75 to 78dB. I sent an e-mail back to that person to confirm their suggestion. The person was positive that every system should be that loud or louder.
To be fair, I know nothing about this person. I did not ask how he arrived to this number range. I have no idea as to how he measured the sound level of a minister speaking in a sanctuary. Also, I did not ask if he measured his minister speaking in a small room like an office or living room. However, are there are a few assumptions we can make?
If a person makes such a statement, by what criteria were they made? Was an accurate meter used? Was he measuring the signal within 3 feet of the PA speaker he was hearing from or was he measuring from a comfortable distance from the speaker system as a typical listener would be? Does the sound system have so many speaker sound sources that the sound coverage in the church is so uneven that sound levels change 15dB from one place to the next? Did he take measurements from more than 1 place? Did this person check any audio books or even an Encyclopedia Britannica or other reference book to see what they say?
Like I said earlier, I know nothing about this person, nor do I want to make fun of him personally. However, a statement was made and since it was public, it should be challenged. Is he right or wrong? How could you confirm if what he is saying is true. When in doubt, ask for a second opinion. Ask a couple of audio stores and contractors. If that is not enough. Check reference books and audio books like Sound System Engineering by Don Davis or Architectural Acoustics by David M. Egan. If you canít trust these people, then you probably donít believe much of the Bible or what is to follow either. There are also many equipment manufacturers that also provide guidelines and info that would tell you what loud is.

(Electro-Voice has a series of papers called the PA Bible.
To order it, send them a letter requesting the PA Bible Series.
There is a $2.00 fee.
The address is E.V. Inc. 600 Cecil St. Buchanan, MI. USA. 49107.
This the best series on audio and acoustics for learning audio basics.)
If this is not enough, you can do what I did. I went to my Baptist Church and brought 2 Sound Level Meters. One is an Audio Source meter and analyzer, the other unit is a Radio Shack SPL meter. (The Radio Shack meter is one of those gems that pro audio people know is a good product for the money and very accurate in itís operating range. But! They donít publicly admits itís quality because of the many other products that Radio Shack sells than end up in places that some Radio Shack executives agree that those products where not meant for such an applications.) Before going to church, the Audio Source meter was calibrated. At the church, the first thing I did was measure the back ground noise in the church before people arrived. The meter said 30dB. When the ceiling fans and accent lights are on, the room noise increased to 45dB. (For the Techs, we call this value NC, but we used the meters un-weighted or as RTAís. Therefore this was not a true NC value. However, it is a value and test that anyone with the RS meter duplicate.)
This is when things become interesting. Normally, during a church service, all ceiling fans and florescent accent lights are turned off. Under these conditions, we normally set sound levels to an average of about 60 to 65dB. Sure enough, on Sunday morning, that was the average for the first 20 minutes of our ministers sermon. Since ceiling fan controls are next to me, I started to turn them on, one at a time. Within a few minutes, all five ceiling fans were on at a slow speed. A few minutes, I turned on the accent lights. While turning on the fans and lights, I had to increase the average sound level at the mixer. When I check the meter, the new SPL level was now averaging around 70 to 73dB.
What does this illustrate? Generally, it is accepted that good hearing in a church occurs when the signal is 25dB above the noise. Signal being the person speaking, or the amplified voice and noise being the noises in the room and noises within the sound system. (This also includes echoís and long reverb times. Many audio people do not take reverberation into their noise studies and often recommend expensive speakers systems that have excellent dispersion control at the sacrifice of sound quality. Then when the sound system is finished, the church is still not happy and a few years later, the sound system is replaced again and again and...)
If our friend who made the statement is working with a sound system or an acoustical space that is noisy - letís say around 45 to 50dB, then his statement is correct. If this person is a sound contractor and says that all of his systems have to be operated in this range, then he should be avoided. Chances are, his sound system design or connection method is creating a noise problem.
If the church is this noisy, then you have to fix the problems. You have to determine if the noise is mechanical or passive. Mechanical noises are generally from ceiling fans, all lights with transformers, air conditioning and heating systems, washrooms, nurseries, children playing in another parts of the church during service, street noise, airplanes, trains, office phones, digital watches with alarms and candy wrappers. Well, the candy and watch problem is rather touchy to deal with, but the other noise problems can be fixed. Typically. A church empty and all of the mechanical systems working at their maximum load, the sanctuary should have a rating of NC 35 or lower for good listening. When a church is full of people, the average noise will increase 5 to 7dB during a sermon and that is normal.
If the church has a passive noise problem such as - so much reverberation that the signal and noise of two people talking at 10 feet is less than 25dB, then killing some of the reverb time will be most helpful. In fact, if you read about church acoustics in other books, then recommend reverb times of 2.3 seconds or less as an average. My book goes a little further and breaks this down into denominational types. If your church has a reverb time longer than 2.3 second, have someone do about 20 to 50 ETC or Energy Time Curve measurements with a TEF or MLSSA. If the energy reflections in the first 100 milliseconds is greater than -20dB,(If your sound contractor doesnít know what this means, teach him. Youíll be doing everyone a big service.) then there is a room problem that should be fixed. If your church is square, you may notice a similar problem regardless of the RT60.
There are many other variables to consider as well, and those are outlined in my book. Meanwhile, my test at the church was not over. After all of the noisy fans and lights were on for about 5 minutes, I started to turn them off, but the volume of the sound system was kept high. Sure enough, within 2 minutes, an usher and elder of the church asked me to turn the sound system down. Hurrah! I said to myself. Once again Joe blow public has come to my rescue. I keep telling people to trust their hearing. Your hearing is way more accurate than any test instrument. All test equipment can do is translate what we hear into something you can see and nothing more. Once you can see a problem, then you can use Laws of Physics and proven mathematical equations to solve the audio or acoustical problem. Trust your ears!

Conclusion

The average listening level in a church should be 25dB above the noise of the room. Typically, if the church noise levels are under control, good listening levels are generally in the low 60dB range. In some churches, the room noise is so low, that a PA system is not needed for speech or a good listening level of 55 to 60dB is OK, (but this is so rare.) If you have to always drive your sound system higher than 68dB, chances are you have a noise problem that needed to be address.
One more thing. Since many church populations have a high number of people with hearing problems, background noise becomes a greater problem. Generally I use the following as a guideline. If more than 60% of the church members or over 60 years of ages, increase the signal to noise (S/N) ratio standard from 25dB to 30dB. This allows many older people with minor hearing losses to hear better without driving the sound system harder and offending others with average hearing abilities. If these people continue to complain, then they will need a personal hearing impaired system of some kind.

Some statements and Specs have been blanked out under the understanding that it is part of the "intellectual Knowledge" guidelines and were not part of the original article. Such knowledge has value and can be purchased through investing in the book ""Why Are Church Sound Systems and Church Acoustics So Confusing?"Info on a book on Church Sound System & Church Acoustics

Back to THE LEARNING CENTER

Church Sound Network
63 Lockerbie Avenue, Toronto, Ontario Canada M9N 3A3

For questions or comments, our e-mail address is - jdb@jdbsound.com

Copyright (c) 1996 JdB Sound, Acoustics.