ICEinLAVA's Domain

Acoustic reinforcement is our primary task as sound system operators. But to the layman, we are perceived as the dispensers of loudness. To him, our job is to make the performance memorable and worth the ticket, not just background noise. With all the new technology available to us, I believe we sometimes get lost in technical abstraction to the detriment of the ticket buyers.

To make the point, let us go back a half century and peek at the loudness chart that the physicists Fletcher and Munson created (see chart). Most of us mix for Sound Pressure Levels in the 80 to 110dB region. Note that at these levels, the human ear response is pretty flat up past one kHz, but needs a little less from two to five kHz, and some help beyond 10kHz. But if you are buying loudspeaker Digital Signal Processors these days, you are given the lecture, “flat is good,” and that is the goal of our SPL measurement gear. If you take this to its logical extreme, everyone should be complaining of excessive presence and not enough sizzle in the highs.

To cite an anecdote, a television listener was complaining of how awful a rock concert sounded coming out the TV in his living room. He telephoned a soundman friend who was watching the same show at home, and got the response, “turn it up, loud!” Sure enough, the concert was a direct feed from FOH, where the band engineer was bathed in +100dB SPL. This instance is rare now that televised concerts usually get a feed to a remote truck with an audio engineer mixing at living room levels. But it goes to show you that loudness is a perception game.

The point to take with you is that the gear can be optimized to be flat response, time-aligned, and capable of delivering great volume. But you, the Front-Of-House engineers, are responsible for taking the mix to those ticket holders and making it sound great, not just look pretty on the metering.

Too Much of a Good Thing

Last month, Paul Freudenberg provided information on inverse square law effects on measured SPL, and OSHA’s workplace limits on SPL durations. The challenge is to make use of this knowledge while mixing the show. For example, my usual club FOH position is about halfway in the room, with the stage or dance floor at one end. Typically the closest seating to the FOH speakers is two “halvings” towards the stage from the FOH position, or about +12dB SPL more than I measure at the console. This means that the closest seated patrons hear more than twice the loudness I do during the show. So the nagging question is, “could I stand the loudness if I were seated in front?”

That is why metering SPL is a good technical guide to remind you of the nagging question. Of course OSHA is not likely to shut down the performance, but they might give you and the venue employees a stern lecture on day after day exposure, and how wearing ear plugs is a good habit to start. In monitoring SPL, choose the C-weighted scale, as it best fits its purpose at levels of 85dB and beyond. C-weighting is flat from 80Hz to three kHz to match up with the Fletcher-Munson curves at louder levels. The A-weighted scale is intended for quiet readings typically in the zero to 55dB range, and has the 300Hz and down information filtered out to match the Fletcher-Munson curves at low SPLs. There is a B-weighted scale to handle the intermediate SPLs, but it is rarely used.

A-weighted SPL meters are more likely to be used by law enforcement officials when checking into disturbance calls. Many communities have evening restrictions on nuisance levels, such as no more than 60dB SPL, A-weighted, at 100 feet from the offending source. This also should be a factor in your loudness judgments inside thinly walled clubs or outdoor gigs.

The Neighbors, The Lawyers

This modern, litigious society is no longer laissez-faire about loudness and how the youth are ruining their hearing. “So sue me, baby” is no longer a light-hearted quip, but a reality in the live entertainment business. We have tobacco lawsuits, fast food lawsuits, and soon we’ll have concert lawsuits. I find it more than amusing that the lawyers are trying to curb the true cause—things that the producers are marketing and the consumer desires. Whether it is concerning soothing cigarettes, tasty burgers, or a loud, exciting concert, the notion that personal responsibility moot offends me.

Let me cite a couple of related examples creeping towards litigation. One sound guy I know lives a couple miles from the Rose Bowl, and if conditions are right, he can hear concerts in his backyard. What about the folks who live closer? In the 1920s when it was built, the nearby residential neighbors could expect to hear the Saturday afternoon roar of a football crowd and a marching band. But do today’s Rose Bowl neighbors have the right to complain if a rock concert is held in the same venue under reasonable SPL and time-of-day restrictions? Residents can and have gone to both the city and the courts to stop shows but I say, if you bought a house in that neighborhood, you chose your fate, and you just have to live with No Doubt cranking it out at 50dB SPL on your lawn at 10 p.m. Now 50dB SPL is half the loudness of a quiet conversation; but if you do not appreciate the particular genre of music and like to sleep with the windows open, you have a problem.

The other example is the debate in my area about a proposed amphitheatre being built on a former garbage landfill facing into a Mississippi river wildlife refuge. The landfill will not be suitable for other residential development. Opponents cite that the noise will disturb the habitat of the refuge. I say this is a perfect amphitheatre spot—not only are there no human neighbors, but the river bottom wildlife will be disturbed less than one percent of the time because of the seasonal use and the few shows per year. If the deer population can’t handle an occasional Ted Nugent concert, I know Ted has a solution to that problem, without activists engaging the services of lawyers. I find the location also ironic, as it is just a couple miles from the Telex—EV, Midas, Klark-Teknik—plant, equipped with a two-story anechoic test chamber so quiet you can hear the blood flowing near your cochlea.

So beware of the gaze of the law professionals, as they see excessive loudness as a vice to be controlled. Like the other precedents of tobacco and fast food, the “low hanging fruit” will be first to be sued. This will likely be event promoters, venues, sound companies, and speaker manufacturers. A couple of future scenarios can be envisioned. One is that FOH console operators will be forced to sign SPL responsibility forms indicating that they shall not exceed a specific reference level or they will be liable to loudness lawsuits. Another scenario could entail DSP SPL monitoring at multiple locations and some kind of limiter/governor circuit taking control of the mix loudness from the console. The industry has spent nearly a century developing ever more efficient loudspeakers. Now those same manufacturers have to shore up their legal defense funds, and teach us users to keep our patrons safe from hearing loss.