Officer: Excuse me sir, do you have any idea how fast you were driving?
Me: Officer, I swear I didn’t know I was speeding.
Officer: The neighbors can hear you seven miles away, and that’s across two rivers, a Christmas tree farm, a football stadium and an asylum for unstable musicians. I’ll have to take you in.
Me: Please officer, don’t take me in. I need this gig. So… exactly how fast was I going?
Officer: 118
Me: 118??!!! That’s impossible. This thing can’t even squawk out a hundred.
Officer: Sir, you’ll have to come with me…
Yikes! But we’re talking 118 dB here, not MPH. SPL limits — I like to call them speed limits — exist at venues for a variety of reasons. The most popular answer to our survey is noise complaints from the neighbors, but there are other legitimate reasons for SPL restrictions. The venue might be a landmark theater and management does not want to risk structural damage that could result from excessive sound energy. There may be other venues in operation nearby such as might be found in a multi-stage festival, or a state or county fair, and the speed limit is intended to keep artists and patrons from disturbing each other during simultaneous performances (yeah, right). When a concert is held at a horse racing track, loud noise may scare the horses.
And of course, there is always the concern of hearing damage to patrons who don’t realize they might be hurting themselves — sorta like mandatory seatbelt use. That last one seems to be less of an issue here in the States than it is in Europe. In the U.S., I have never encountered an SPL limit for OSHA compliance (certainly not a bad idea), but if I recall correctly, it’s the Sweden Rock Festival that maintains an SPL limit to comply with government regulations for limiting public exposure to excessive noise. It’s probably not such a bad idea to limit your exposure to high sound levels, since this is your livelihood.
Regardless of the reason, the net result is the same: sometime you’re going to have to play by the rules and keep down the racket. Doing so is smart for legal reasons, for hearing protection and for keeping the gig on the calendar next year. If you can’t play by the rules, the venue may not invite you back. If the band loses the gig because you’re too loud, at the very least, you’ve lost a day or two of work next year. At worst you might be fined or lose your gig.
Where’s the Sign?
The first part of dealing with a sonic speed limit is knowing it exists. I love the surprise I get once or twice a year when I roll the intro at the start of a show and someone comes up to me and says “So-and-so told you that the limit is 95 dB here, right?” Umm…no, and you picked a helluva time to tell me. I try to make that question part of the advance, but most venues will let you know ahead of time. These are the things you need to know about noise restrictions: What is the specific SPL limit? Where and how will it be measured? What are the guidelines for the measurement? What are the consequences for exceeding it? Does the house tech have any suggestions for dealing with it?
An SPL measurement should be taken at the front of house mix position but that’s not always the case. Let’s face it —if the mix position is ten feet in front of the stage and the limit is 95 dB, you’re done before the first note. (This reminds me of a show I did in San Angelo, TX many years ago.) However, if that same 95 dB is measured at a mix position 200 feet from the stage, that really should not present a problem. Up next: How is the measurement made? The Radio Shack SPL meter is ubiquitous, dependable and reasonably accurate; and even when there’s no speed limit, you should know how fast you’re driving anyway. If you don’t have an SPL meter at FOH, you can’t know if you’re’ breaking the law. I’m always suspicious when I see a mic on a stand near the FOH desk, plugged into an interface and computer running audio analysis software. Did anyone calibrate the mic for an accurate measurement? Often not. Gimme back that Radio Shack meter!!! Some venues, such as the Pacific Amphitheater, have a measurement system that is very accurate, and I prefer it that way.
The Long and the Short of It
A venue may perform LEQ (Equivalent Continuous Noise Level) analysis, a long-term average noise measurement — so you get some grace regarding brief peaks and transients. In such a case the rule may be more of “do not exceed 102 dB SPL for more than X amount of time or we have a problem,” as opposed to “do not exceed 102 dB, ever.” You might see a computer screen at FOH that displays the measurement in real time, and the entire screen may flash yellow when you’re close or red when you’re over the limit, all of which is very helpful. Other venues literally have a sound cop — an officer who strolls past FOH periodically during the show with a handheld meter and checks your level. In that case you still need a meter at the desk during the show. If possible, run noise through the system during sound check to make sure that your meter agrees with the meter that will be used as the reference speedometer.
He Ain’t Heavy, He’s My….
Another piece of the puzzle you’ll need is the weighting of the measurement. SPL meters typically perform A-weighted or C-weighted measurements. A-weighting causes the meter to respond primarily to frequencies in the range from 500 Hz to 10,000 Hz (the human ear’s most sensitive range), traditionally making it more useful in measuring noise levels. C-weighting extends the range down to 32 Hz. This is more accurate for measurement of music because it increases the meter’s sensitivity to low frequencies. C-weighting was originally intended to mimic behavior of the ear at higher sound levels, but in practice, A-weighting is probably more widely used.
Why do you care about weighting? There are several reasons. First, you need to know the weighting for consistency of measurement. Secondly, for a given “volume” level of music through a P.A. system, an A-weighted measurement will be significantly different from a C-weighted measurement. The difference will be that the A-weighted SPL will probably be lower because it ignores the lower octaves — the frequency range where a lot of power exists in a mix. It’s much easier to maintain an SPL of 100 dB A-weighted than 100 dB C-weighted. If Sound Cop is using a C-weighted measurement, he may clock you at 105 dB while your A-weighted meter may show 97 dB. “I didn’t know” is not a valid defense.
Time Off for Good Behavior
I’ve mixed in many venues where the Sonic Speed Limit is initially laid down as a law, but relaxed later. A casino that I’ve worked for close to 15 years has an SPL limit of 98 dBA at front of house. The first time I mixed there, the systems tech explained the rules and kept an eye on me (and the meter). Of course, I heeded the rule. Over the next few years, I surmised that it was more about not being out of control and pissing off patrons who were gambling in nearby areas. That’s not to say that I abuse the privilege, but when I mix there, I’m politely reminded of the speed limit and not watched over, because the systems tech knows I respect him and the venue — and that’s part of why the gig remains on the calendar year after year. In other words, sometimes the rule is there to make sure you don’t get out of control.
Your efforts to heed the law will be influenced by the band’s stage volume, but keeping that to a manageable level is a discussion for another time. In the meanwhile keep yer eye in the rear view mirror.
