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SPL’s: Playing by the Rules

Steve LaCerra • July 2020On the Digital Edge • July 10, 2020

Most people like loud music, and part of the attraction for concertgoers is hearing their favorite artist perform at sound levels far exceeding what they can conjure up in their living room — whether it’s due to the limitations of their home audio gear or the limitations of their neighbors’ patience! As much as we’d like to have complete artistic freedom and be able to crank it up as loud as we want, sometimes that’s just not possible. There are more than a few scenarios where you might have to keep the SPL down to what venue management considers “reasonable.”

The bottom line is that it doesn’t really matter why there’s an SPL restriction at a venue. What matters is that, if you want to have a good day and be invited back to the venue next year (i.e., another paying gig), you need to play by the rules.

›› What Are The Rules?

To be able to play by the SPL rules, you must know the SPL rules. This is not as cut-and-dried as it may sound. I remember being in a situation where a club owner never cleared with local authorities the idea of erecting an outdoor stage in the parking lot, and was then surprised when the police came down on him like a ton of bricks after a show started. He came running up to me during the show screaming about the SPL limit. What SPL limit? There was no discussion of this at any point prior to the show. My reaction was, “Well, tell me how loud is too loud. Give me a number: 85 dB? 110 dB?” Heck, I can mix either way — though truth be told, the band was way loud on stage. He looked at me like I had three heads, because he had no clue. I’m not going to play the game of, “It’s too loud because I say so.”

That’s why it’s important that restrictions are clearly understood prior to soundcheck. You can’t observe the local speed limit if the town doesn’t post a sign. The measurement location is usually at front of house, which makes a lot of sense, unless FOH is at the side of the stage (shoot me) or at the back wall of the venue (easy to deal with). It’s amazing how many Radio Shack SPL meters are still in service for this purpose. They’re reasonably accurate, rugged devices, though they won’t help you with LEQ (see below). Make sure you have a way of lighting those meters during the show, because they’re impossible to read once the lights go down.

›› Weight a Minute

Any time you measure SPL, you need to be aware of the measurement weighting. Most SPL meters and measurement software permit (at the very least) A-weighted and C-weighted measurements — which display very different numbers under the same conditions. When an SPL meter is for to A-weighting, it responds primarily to frequencies ranging from 500 to 10,000 Hz, making it useful for determining noise levels. C-weighting extends the measurement range down to 32 Hz, making it more accurate for measuring music. That’s because the power of most mixes is concentrated in the bottom end. If you were to run pink noise through a P.A. system, an A-weighted measurement would be significantly lower than if you switched the meter to C-weighting. When I’m told that the SPL limit in a venue is 100 dB A-weighted I’m not that concerned, but if it’s 100 dB C-weighted, then I certainly want to pay careful attention to level of the P.A. as well as the band’s stage volume.

Some venues use a measurement called Equivalent Continuous Noise Level, abbreviated LEQ. This type of measurement averages brief peaks in sound level over a period of time, providing you with a margin of error. Depending upon the venue, the rule might be “do not exceed 105 dBA for more than 30 seconds,” which is very different from “do not exceed 105 dBA ever.” Typically, LEQ is performed over a longer period of time such as an hour (Fig. 1).

Fig. 1: The upper right hand corner of this Rational Acoustics Smaart Di v2 screen indicates it’s set to measure LEQ, A-weighted, over a time period of 60 minutes.

Most handheld SPL meters don’t perform LEQ, so you may see a computer at FOH running analysis software displaying LEQ information. Depending upon the software, the screen might flash yellow when you’re close to the limit, or red when you’ve gone past the limit. At one particular venue I’ve worked, if you exceed the limit by 5 dB, the screen goes black and an automated sledge hammer comes down on your head (just kidding). If you plan to watch your own meter during the show, run some noise through the system during sound check and see if there’s a difference between the house meter and your own.

›› Can Ya Turn It Down?

It can be difficult to stay in line with SPL restrictions but as you might imagine, the key is getting the band’s stage volume down to a manageable level. A long time ago, I had an issue at the RA Nightclub in the Luxor Hotel in Las Vegas. The manager never told us about an SPL limit, and when our show started, he came to me at FOH and asked me to turn it down. I did, but it was still too loud. (If I recall correctly, the limit was 95 dB at FOH. I don’t recall the weighting). I tried to explain to him that the stage volume was exceeding the limit regardless of the P.A., so I grabbed a handheld SPL meter and held it near the drummer on stage. The meter showed 105 dB C-weighted. At that point, I certainly wasn’t going to start changing monitor levels on stage (no one was using in-ears at the time). If we had known there was a restriction earlier in the day, we might have made some adjustments, but at that point, it was mostly out of my hands — so I directed him to the tour manager.

There are times when a venue says they have an SPL restriction, but they’re really more concerned that you don’t scare away the patrons or blow up their P.A. — and defining a limit gives them an out if you push the pedal to the metal. The bottom line? You have to play nice if you want the date on the calendar again next year, so it’s a smart move to make the house manager happy.

Some Reasons for SPL Restrictions

• Local ordinances regarding sound levels.

• Concern over damaging the physical structure of a landmark building.

• Occupational health and safety issues, whereby a venue seeks to protect patrons’ hearing either to avoid legal action or out of genuine concern that patrons may incur hearing damage.

• The demographic of a particular audience may not want to hear high SPLs.

• Interference with the ability for nearby vendors to communicate with potential patrons (like on a boardwalk).

• Consideration for neighbors comes in many forms. Sometimes it’s, “You can’t sound check until 5 p.m., because that’s the end of the work day for the city council next door.” It could be that sound spilling outside of the “bowl” of an amphitheater reaches some very testy neighbors who make trouble for the venue. In casinos, it may be a desire to prevent showroom noise from spilling into the gambling areas, which might impede gambling.

 

Steve “Woody” La Cerra is the tour manager and FOH engineer for Blue Öyster Cult.

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