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Best Threads: SPL Limits At Front Of House
Are there really any hard and fast rules about sound pressure levels or even accurate measurements?
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Editor’s Note: Here’s an interesting thread from the PSW Live Audio Board (LAB) forums. It’s lightly edited for grammar and formatting. Enjoy.

Posted by Jason
I’d like to get some opinions on standard front of house DB restrictions. I’m going from a smaller PA where I didn’t really need to enforce a dB/SPL limit to a new rig that can easily outperform the small rig.

I’m in a downtown outdoor environment and we have brand new high-end residential towers just outside of the venue. 

I see a ton of artist riders, but not many venue tech packs, as I’ve been off the road and at this same venue for 4 years now. It seems like I use to see 105 dB at front of house on the regular.

What does everyone recommend? 105, 100??? A,C weighted?

Reply by Nathan
I would say it depends on the length of the show. You can go louder for shorter. Quieter for longer. I’d go with NIOSH or OSHA limits. A weighted, when weighing SPL that damages human hearing, C gives unrealistic answers.

Reply by Ivan
Technically, A weighting should never be used above 80dB. C can give high numbers if people are used to using A. Basically it depends on what you can get away with.

On a city street, lots of vibrations can get into buildings through the structure, so they may not be able to “hear” it, but they can feel it. It is also not only the scale, but also the response time.  Slow and fast can give a wider or narrower range.

At one recent EDM show I did, the difference between A slow and C peak was 32dB. HOWEVER-when you look at the difference below 100Hz to above 200Hz, the difference was around 42dB.

So-once again- a simple single number does not give an accurate easy answer. So, it depends…

Reply by David
You do know they’re gonna put that on your tombstone, yeah?

Reply by Nathan
Then why are NIOSH & OSHA using it and their charts don’t start until 85 dB? Yes, I realize they are for a 8-hour work day using loud equipment. Yes, I know we assume no prior exposure during the day when we run shows. But it’s what we got.

If you metered things with C at an EDM/rock concert you would absolutely be way higher on the meter than the only published source of SPL restrictions we have. So to be inside the margin you would be forced to run things quite a bit quieter and the promoter/band might not be having you back.

Also, I’m not saying use the chart for peaks, I’m saying use it for an average level. If said concert is 1 hour, then the average level should be below 94 dBA which is pretty easy given how many lulls there are in music.

Reply by Ivan
OK, I was wrong. The upper limit for A is supposed to be 60 dB, not 80 dB.

Just because some people use it does not mean that it is proper or correct. I was simply stating the level of the original intended curves were. Here is another reference, if anybody is interested.

Reply by Jason
I’ve always been confused by people’s choice of A or C weighting. “A” makes sense to me, considering I’m more worried about what people are hearing as opposed to getting truly scientific data.

For example, I had a local guy who thinks he’s an audio guy post something on social media after a show at my venue. The headliner actually brought their own PA for that show, but regardless he was posting on social media that the show was 137 dB, even posting a picture of his phone app he says he calibrated in his studio.

He was using C-weight and was about 16 feet from 8 SB1000’s. Had he used A-weight, it would likely have been closer to 110 or lower, still too loud, but fairly normal in regards to concert audio.

I’m wanting to find a good compromise where I can keep the SPL at a reasonable level while at the same time not restricting visiting engineers into a unrealistic set of rules. I’m not worried about system protection, as I’ll have tons of headroom and the ability to clamp anyone down who may be pushing it too hard.

Reply by Tim
You’re trying to prevent problems with neighbors who have more political and monetary capital than your venue is willing to risk. Good luck, because if you fail, the City Commission will have your board reading a “nasty-gram” from a bunch of lawyers.

The easy answer is to use whatever SPL level was not objected to previously. If the old rig got no complaints at (arbitrary number for discussion) 95 dBA, slow, then use that until you feel more adventurous and/or have a better feel for the neighbors’ attitude.

As far as BEs… most of them get it when you tell them about the SPL limit. A few will scoff and a few will ignore it and you. I’ve worked a restored historic theater with a 95 dBA fast limit. The national acts simply ignore the theater director unless they’re already performing that way…  Others will do their best to accommodate the limit but they struggle.

The potential for over-limit use starts with booking. Ricky Lee Jones or the Man o’ War tribute?

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