One of the issues that sound engineers deal with on a daily basis is that of hearing conservation. In the United States, advocates for employee safety such as OSHA (Occupational Safety and Health Administration) and NIOSH (National Institute for Occupational Safety and Health, have set very specific guidelines for avoiding hearing loss due to exposure to loud noise. And let’s face it: Many sound engineers work under constant conditions of “loud noise.” Research by such organizations has produced a plethora of data regarding hearing conservation, some of which refer to the amount of time a person can be subjected to loud noise without damaging their hearing.
As an example, NIOSH research has produced a recommended exposure level (“REL”) of 85 dB, A-weighted as an eight-hour, time-weighted average. According to their studies, exposure to noise at or above this level or length of time is hazardous to long-term hearing. NIOSH publication number 98-126 Criteria For A Recommended Standard: Occupational Noise Exposure, Revised Criteria 1998 features a chart of maximum safe ex-posure times versus dB levels. An increase of 3 dB SPL above the 85 dB REL essentially requires the exposure time to be cut in half. So, if you are monitoring at 88 dBA, your exposure time should be no longer than four hours; at 91 dBA exposure should not exceed two hours.
It’s not hard to see that by the time we reach real-world concert SPLs, the REL can be calculated in terms of minutes: At 105 dBA, exposure should be no longer than four minutes and forty-three seconds. Any longer, and you risk your hearing.
This Danse Macabre is relatively easy in the studio. When mixing with band members in the control room, I have run into complaints that the control room monitor level is not high enough. Too bad. I kindly explain that I cannot work for an extended day at louder levels. I also show them where the volume knob is, as I stroll out of the control room and into the lounge while they listen at ear-plastering levels.
Unfortunately, we cannot do this at a live performance. The audience at a typical Justin Timberlake show is probably screaming at an SPL of at least 100 dB, and you have to pump the PA above that din just to hear the band (or track, or whatever).
I’ve used many odd “techniques” to deal with this problem over the years: mixing shows with foam ear plugs, mixing shows with custom-molded attenuators, mixing shows with no plugs. Then there are the silly variations: mix the first 10 minutes of the show without plugs, put plugs in for five to seven minutes, then take one plug out. Start the show with both ears open and then put plugs in alternate ears every 10 or 15 minutes for the duration of the show. An annoying game, and a distraction to the mixing process, but I’m really not getting paid enough to damage my hearing, thank you very much. I swear one of these days, I’ll mix a show where there’s a 1/4-inch stereo jack at every seat, and we tell the audience to bring their headphones because there won’t be any PA.
Over the past 15 or so years, musicians have become hip to the fact that the personal monitor can help them avoid exposure to loud noise. When implemented properly, the ear is sealed from ambient noise with a tight-fitting plug. The plug has a small built-in driver through which we can send a mix, but since the ear has been sealed from outside noise, the level of the audio signal sent into the ear can be made very low, thus preserving the hearing.
Recently, Sensaphonics (www.sensaphonics.com), a company specializing in custom personal monitors, introduced a product called the 3D Active Ambient personal monitor system. The 3D (patent pending) differs radically from other PMs because it was designed to solve a problem that many performers have expressed regarding PMs: the feeling that they are isolated from the audience and other performers when their ears are plugged. It’s not hard to understand. Many IEM engineers have juggled chainsaws to solve this issue, placing audience mics in the house or at the front of the stage and feeding them into the ear mix, or perhaps sending the entire house mix back to the ears.
The 3D Active Ambient System solves this problem by incorporating subminiature, precision-equalized microphones into the earpieces, allowing the listener to hear ambient sound with the correct directionality and natural sound quality. When a person wearing the 3D Active Ambient System moves their head, the mics move with them, preserving correct directionality relative to the environment. Plus, the performer has the ability to balance the amount of ambient sound against the “direct” feed of the monitor mix.
And therein lies the interest of the front-of-house engineer. How about using the 3D Active Ambient System to seal one’s ears off from the raucous din of the room — the high SPL — but then open up the ambient feed so that you can hear the house sound via the ambient microphones, but at a safe volume level — anywhere from unity gain down to -24 dB. Or turn the ambient mics off (a simple toggle switch), so you can check the solo bus in isolation. Brilliant!
With a tool like the 3D, you can still hear the room, naturally and acoustically, so the quality of the mix is not affected. But now, you can adjust the ambient level like a volume control for the room. You could mix an eight-hour show every day without risk of hearing damage.
Now that’s technology at its best.
Steve “Woody” La Cerra is the front-of-house engineer and tour manager for Blue Öyster Cult. He can be reached via email at Woody@fohonline.com.
