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 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 can't trust these people, then you probably don't believe much of the Bible or what it is to follow either. There are also many equipment manufacturers that also provide guidelines and info that would tell you what loud is.
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If this is not enough, you can do what I did. I went to my Local Church and brought in 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 it's operating range. But! They don't publicly admit it's quality because of the many other products that Radio Shack sells than end up in places that some Radio Shack executives I have meet 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. Therefore this was not a true NC value. However, it is a value and test that anyone with the RS meter can 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 62 to 69dB. 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 turn them on, one at a time. Within a few minutes, all five ceiling fans were on at a slow speed. A few minutes later, 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 I was trying to do was set the level to be 20 to 25dB above the noise. This was all done with the minister permission. To make sure I was not putting my own spin on things, I had other church members who assist in running sound to do the same adjustments while I was turning the background noise up and down. Again, all of the sound techs were trying to mix the speech to be 20 to 25dB above the background noise.
What does this illustrate? Generally, it is accepted that good hearing in a church occurs when the signal is 25dB above the noise. You can do this if the noise is below 45dB or NC35. Signal being the person speaking, or the amplified voice and noise being the mechanical noises in the room and noises within the sound system. )
If our friend who made the statement is working with a sound system or an acoustical space that is noisy - lets say around NC 45 to 55, then his statement is correct. But that only amplifies the problem that the background noise is much too loud and at those levels, long term listening becomes very uncomfortable. I have meet people who avoid churches that run speech at those levels.
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 15dB, then killing some of the low frequencies of the reverb time will be most helpful.
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 an elder of the church asked me to turn the sound system down. Hurrah! I said to myself. Once again laypeople were speaking up and have 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 or quantify and nothing more. Once you can see a problem, you will better know how to solve the audio or acoustical problem. Trust your ears!
The average listening level in a church should be 20 to 25dB above the noise of the room. It is that simple. Typically, if the church noise levels are under control, good listening levels are generally in the low to mid 60dB range. In some churches, the room noise is so low, that a PA system is not needed for speech for a room of about 500 to 800 people(this is typical in well behaved rooms.) If you have to always drive your sound system higher than 70dB as an average level for speech, 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 are over 60 years of ages, increase the signal to noise (S/N) ratio standard from 15dB to 25dB. You can only do this if all background noise is below 40dB. 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?" which is now out of print
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