Don't Fear the Sweeper: Audience Scanning in the US

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Apr. 28, 2010 — You're standing in a field with a thousand or more of your close friends, the ground beneath your feet quaking in time with the bass emanating from a thunderous sound system. A cone of light appears, a solid green sweep generated by a nearby laser. It expands rapidly and envelops you and your friends in its preternatural glow. The green gives way to a wash of other colors; the cone shrinks to a thin plane, slices of fog dancing through it. From somewhere above, a puzzle of light descends to meet you. Individual beams search you, play around you, involve you.

Laser light displays that incorporate audience scanning have a proven safety record. Still, they are rarely seen in the US. (Photos courtesy of the International Laser Display Association. Used by written permission. All rights reserved.)

The history of audience scanning — in which lasers are beamed into a crowd during a show or display — can be traced back to the early days of lasers in rock concerts. Patrick Murphy, executive director of the International Laser Display Association (ILDA) points to Blue Öyster Cult shows in the mid-'70s as some of the earliest instances of the practice. During the band's Agents of Fortune tour, a lighting engineer would shine a laser — a raw beam — onto Buck Dharma's guitar. Dharma, naturally, would then aim it at the audience as he played. (Music sociologists, who already think of the electric guitar as the ultimate phallic symbol, would have a field day with this one.)

Shows incorporating audience scanning — at discos and raves, for example — are a bit more sophisticated today, and a bit less reckless. Audience safety is now actually a concern. Still, by and large, you won't find the shows in the US. This is partly due to regulations put in place in the wake of the Blue Öyster Cult concerts, among others.* To attribute it to these alone, though, would be a mistake.

The fact is, Murphy said, regulations are largely the same the world over. The reason we don't have audience scanning in the US is twofold: First, the regulations are more strictly enforced here than elsewhere. But also, there's the general culture of litigation and safety precautions in the States. Many who stage laser light shows choose not to incorporate audience scanning because they fear the potential legal and public relations ramifications of an injury claim.

That's not to say that audience scanning isn't possible within the Maximum Permissible Exposure (MPE) established by the FDA. It is, but the effect at these levels is relatively dim. At the same time, the increased beam divergence produces "fuzzy" beams with soft planes and cones of light. The displays therefore can come across as less exciting to those attending the shows.

To address this, and to create conditions favoring use of audience scanning, ILDA has proposed a new category of audience scanning show allowing up to 10 times the current MPE under specific conditions. These would include safe show content, accurate measurements of the beam, cautionary warnings to the audience, and increased liability exposure. In conjunction with this, ILDA would ban audience scanning at any level above 10 times the MPE.

Murphy hopes that laser light show companies and venue operators will agree to these changes. "If they understand the reasoning behind 10x, then they may be willing to 'bend the rules,' " he said. "Given that the rules are too often broken by laserists who don't understand or don't care" — shows in Europe routinely use levels 10, 50 and even 100 times the limit — "even just bending the rules is an improvement for safety." Of course, venue operators will also have the option of staying within the established MPE.

He emphasized that, despite the fact that so many audience scanning shows exceed the MPE, an average of only 2.5 incidents per decade have been reported in the past 30 years for shows using continuous-wave lasers; during this time, at least 110 million people have attended the shows. (Injuries have been reported for displays using pulsed lasers — at a 2008 festival outside Moscow, for example (See: Wrong Laser Aimed at Crowd). Using pulsed lasers for audience scanning violates all kinds of regulations, though, and flies in the face of common sense.) Even conservatively accounting for 90 percent underreporting, he said, that would be only 75 incidents over three decades.

"I don't want to get cocky — people need to do shows safely, and to know what powers they are putting in the audience — but in terms of adverse vision effects being reported by audience scanning laser show attendees, it's pretty amazing that [the injury rate] is so low compared to other entertainment activities. For example, in three decades there have been 216,000 injuries and 132 deaths from amusement park rides in the United States alone."

Ultimately, ILDA would like to change the regulations. They hope to begin talks with the Center for Devices and Radiological Health at the FDA, to find ways to reduce the burden of variances on regulators as well as on laserists, while maintaining public safety. "We will do what we can," Murphy said. "We understand FDA and CDRH have some more pressing issues, where there are actual or potential public health concerns much, much larger than laser light shows."

*Eric Bloom, Blue Öyster Cult's singer, recalled in a interview: "OSHA sent a representative to several shows for several weeks, measuring the light during sound check, making reports. At the end of our tour, our lasersist (sic) went to Washington to meet with a panel and was presented with reports on why we couldn't use the lasers anymore…It was too dangerous. There are apocryphal stories out there. Someone said to me, 'I heard you got sued for blinding some guy.' But that never happened." The band was eventually allowed to resume its laser light displays, though without the audience scanning effects.

An interesting aside: A 1977 issue of Billboard magazine noted that David Infante, the laser physicist hired by Blue Öyster Cult to design its laser light show, whose company was outfitting the still-unopened Studio 54 with a laser light system, had recently fired back at critics of the new lighting concept — emphasizing the stringent guidelines put in place by OSHA and the recently launched State Laser Commission of New York. At the same time, noting the possible misuse of lasers by lighting manufacturers, he recommended that club operators check the reputation of the manufacturer from whom they are considering a purchase and consult with either OSHA or the State Laser Commission of New York as to the design, power and application of the system.

Published: April 2010
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications light can be considered to cover the nonvisible portion of the spectrum which includes the ultraviolet and the infrared.
Audience scanningBlue Oyster CultBoasConsumercrowd scanningDavid InfanteDifferent WavelengthsDisplaysGaryGary BoasGary Boas BlogILDAInternational Laser Display AssociationLaserslightMPEMurphyOSHAPatrickPatrick Murphypulsed lasersRussiashow

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