Your ears are not a hundred percent reliable, at least when it comes to hearing loud sounds over long periods of time.

So, if you're running sound at church, that's why you need an SPL meter at the sound booth.

But which one do you choose? What settings do you put it on? And what are you looking for? If you're looking to buy a new one today, we'll answer all those questions.

Why can't you trust your ears to tell you how loud it is? 

There's a story about a guy who's driving home when it starts to rain. He turns on his windshield wipers and turns up the radio. It's coming down really hard, so he has to turn up the radio a little bit more.

When he finally gets home, he goes inside and goes to bed. The next day, he comes out to his car and thinks that somebody has broken in and cranked up his stereo. He thinks, "There is no way he had it that loud."

Temporary Threshold Shift

This, my friends, is the result of a temporary threshold shift. When we're in a noisy environment for a long period of time, things that don't seem that loud can actually be quite loud.

This can happen to you if you've been around loud machinery at work, and then show up at church for evening sound check/rehearsal. Temporary threshold shift is a phenomenon that happens when we're exposed to loud sounds. To protect our hearing from being damaged, our middle ear will adjust so that we have a higher threshold, or it takes more intensity to perceive sounds at the same level.

Usually, a temporary threshold shift goes back after a few hours or, in less fortunate cases, a few days. But your ear does recover over time. The problem is that you might be mixing right in the middle of one of those times, or mixing might create that temporary threshold shift.

You can get permanent hearing damage if you ignore the effects of temporary threshold shift and continue to expose yourself to too much sound pressure level. And that doesn't come back without a creative miracle.

So we must have a good grip on how loud things are and know how long we've been exposed.

Different People Mixing

Another reason you can't just use your ears and probably want an SPL meter is that different people are in the sound booth. Most likely, different people mix from week to week, and it can be challenging to get a consistent volume level for each service. You want to set the same general targets for how loud it sounds during service; the SPL meter can help you achieve this.

Communicating this general sound level with your team can help create consistent volume levels across every service. Remember: Consistency is key. 

What does an SPL meter measure?

An SPL Meter has a calibrated microphone inside that tells you how much intensity is happening at one particular spot, namely where that microphone is. It's calibrated to a certain number of joules per square meter, so it's the amount of energy on a flat plane in one place.

Different settings on your SPL meter tell you different things for different environments.

The first setting we'll discuss is the fast and slow speed. The fast setting will tell you the instantaneous peak of a specific measurement, averaged over about a quarter of a second. This setting is more sensitive to transients, like drums or acoustic guitars.

Slow weighting, however, averages it over about a second and sometimes a second and a half. It shows less emphasis on the transients and more on the “average levels” happening over time.

I have to put quotes on “average levels” because when we're talking about sound waves, sound waves are oscillating particles that are going back and forth. Because they're wiggling back and forth, if we take the average pressure of that, the average ends up being about zero.

The slow setting is more about the average levels and takes into account the transients, but a little less so. This is more like how our ears perceive sound. We will perceive levels on an average level much more than absolute peaks.

Weighting Network

Another thing we want to look at with our SPL meter is the weighting network. This determines what part of the frequency spectrum our SPL meter will focus on or what parts it will ignore.

Now, if you've watched my channel for any length of time, you've probably seen me use the Fletcher Munson curve.

This shows that our ears will perceive different frequency ranges at different intensities at different balances. The short story is that it takes a lot more low frequencies to be perceived at the same level as upper and middle frequencies.

Putting our SPL meter on the A-weighting network will filter out the lower frequencies to which we are less sensitive and focus more on the middle and upper frequencies to which we are more sensitive.

If we choose the C weighting network, it will include all the low frequencies at their absolute intensities, not at our perceived intensities.

So, if you're worried about how loud it is for people's hearing safety, I recommend using A-weighting.

If you want to get the overall energy and know what your subs are pushing relative to everything else, you could use C weighting, but I don't typically use it.

My brain just kind of works in A weighting for perception and reading the meter at the same time. 

There are other weighting networks, but they go beyond the scope of this blog, and I don't fully understand them. If you want me to do a deep dive into them, shoot me an email ([email protected]), and I'll see if I can do some research and make a detailed video or blog post about them.

Time-Weighted Averages 

Another way to measure intensity over time is to use time-weighted averages. This goes beyond what your simple handheld SPL meter will show you and requires a program like SmaartSPL that can gather data from a calibrated microphone and interpret that data in various ways.

With SmaartSPL, you could display a bunch of different SPL meters and numbers on the screen to give you a bigger picture of your levels and how long they have been at that range. You could show a 10-second average or a 10-minute average. Those are all factors that go into how long people have been exposed.

Many of our services are very short in the church environment, right? Typically, there are 30 minutes of worship. But some people have longer worship services, and that's awesome.

I don't think everybody has to conform to a cookie-cutter image of what worshiping and gathering on a Sunday should be.

However, if you're in one of those churches where worship lasts about 30 minutes, you don't have to be terribly concerned about damaging people's hearing with noise exposure until you're getting into the 92 to 95 dB SPL range.

There are a lot more details that go into this. Here are the NIOSH exposure recommendations for different SPLs and the times.

NIOSH Time Weighted Average Limit Recommendations: For each 3 dBA increase in noise level (measured in SPL Slow, A-weighted), NIOSH recommends reducing the exposure duration by half.

85 dB-A - 8 hours

88 dB-A - 4 hours

91 dB-A - 2 hours

94 dB-A - 1 hour

96 dB-A - 30 minutes

99 dB-A - 15 minutes

Read more here: https://www.cdc.gov/niosh/topics/noise/noise.html

But if you're in one of those churches where you really like to push it, which is fine, you must also be aware of yourself and how it is affecting you. During soundcheck or rehearsal, if you're exposing yourself to too much noise you can end up damaging the only window you have to enjoy and mix music.

I don't want that for you, so please be careful how much noise you're exposed to and really track this stuff down.

Where does the SPL meter fall short?

In essence, the SPL meter cannot judge tone. We could make something very harsh, very unpleasingly thin, and nasally piercing, and that would not measure as high on the SPL meter. Alternatively, a big, full mix with lots of low-end support could measure louder but feel much more comfortable and less damaging to your hearing.

You have to watch the meter for a minute to know where you're averaging. Even though we set it to a slow speed, it's not entirely accurate in every single number it hits.

I try to take note of the average numbers that I'm hitting during a big chorus and maybe where it peaks the most, but I'm not worried so much about those peak levels as I am about the average levels I'm hitting.

Try Mixing in Quiet Moments, too.

A simple SPL meter also doesn't tell you how long you've been loud. One of the things that I recommend if you're mixing and you want to mix loud is to make sure that you're mixing in quiet moments as well. It's going to take coordination between the sound team and the worship team to create dynamic arrangements—and don't just stay at a “10” the whole time.

They come down for a little while so you can have some contrast, and people's ears can catch a break. Also, unless you get an SPL meter that's precisely calibrated, I would use these as a guideline and a consistency tool rather than an absolute this is a “precise safety” tool.

Companies do sell calibration devices, but those can get pricey. Some less expensive SPL meters don't even allow you to have a trim function to set the SPL or whatever it is when you're calibrating it. 

Which one should you buy?

If it were me, I would make sure I'm reading a lot of reviews - and reviews from people who are using it the same way that I am.

I care about airplanes, trucks, and other such things, but not as much as music. I want to read reviews from people who are using the SPL meter for music.

If you're in a climate-controlled church environment, I would go for one that's a little bit more repeatable in its results rather than being absolutely accurate and calibrated to something.

Of course, you don't want it to be way off. You should have some idea of whether or not it's close to something that's actually calibrated.

Now, speaking of calibration, you might wonder, “Can I just download an app for my phone?” 

I don't mind if you do that, but please know the limitations of your phone's microphone.

It's not meant to pick up low-end, even though you're kind of ignoring low-end with your A weighting. It's also not really meant to capture transients, even though we're kind of not trying to capture transients. But your phone's microphone probably has a bunch of dead skin cells and lint in it from being in your pocket.

Why would you trust your mixing decisions to something set up like that?

I personally wouldn't.

You can if you want. But if you come up and show me your phone SPL meter, I won't pay much attention to it.

Here are some of the best SPL Meters for churches I would recommend.

SPL Meter Recommendations

Extech 407730 Digital Sound Level Meter - https://amzn.to/3RFY4xC

This one from Extech is really solid, and I like that it has auto-ranging.

Galaxy Audio Check Mate - CM-130 and CM-140 SPL Meters - https://sweetwater.sjv.io/3eWRNA

There are a couple of Galaxy Audio ones. These two by Galaxy Audio are available at Sweetwater, and I like the more expensive one because its range is a little bit more useful. I don't like having to set the range that I'm in in the different parts of the worship set. I just want to turn it on and know that I'm good to go without having to hit one more extra button.

ERICKHILL ES100 Sound Level Meter - https://amzn.to/4ai5C0Y

Another budget option is the Erickhill ES100. It's got other features like temperature and humidity. I suppose you could watch the temperature and humidity go up as people come in after the service starts rather than what it's like during sound check. But if you're not setting up things where you're time aligning your speakers, it might not be a feature that you need.

So, if you buy a new SPL meter, which one will you grab? Don't forget to make sure it has A weighting and slow. That's really what you need to know.

I pray this blog post blessed you. Remember: It's all about the low end; avoid the sound tech solo, and nobody leaves church humming the kick drum.

Stay frosty, Sound Ninjas,

James