In between mixing FOH for (and tour managing) Blue Öyster Cult, our ace correspondent Steve La Cerra comes up with some highly utile — and always entertaining — writings on audio basics in his “Theory & Practice” column, found on page 57. A couple weeks ago, we chatted about a topic for this month’s entry and decided that something about gain structure and dynamic range would be appropriate. After all, these are two fundamentals that play an essential role in achieving good sound, yet sometime cause confusion when mixing (pardon the pun) reality with theoretical abstracts.
Simply put, the dynamic range of an audio system or component can be defined as the difference between the level of the din of noise and the maximum level achievable. In a non-amplified, all-acoustic performance, this is range between the threshold of hearing and the maximum SPL’s the performer or ensemble can muster. This can vary depending on the venue’s noise floor, reduced by air handling systems, ambient noise and even audience sounds, such as the guy with the crackling candy wrappers sitting next to you. Another factor is the distance from the listener to the source — the closer you are, the greater the achievable dynamic range.
In terms of electronics, one of the simplest cases of defining dynamic range may be a condenser microphone that is capable of capturing 140 dB and the self-noise of the onboard mic electronics is 26 dBa, then that unit’s dynamic range is 114 dB (140 – 26 = 114).
If only life were so simple and we could always live in a theoretical vacuum. Unfortunately, before we can translate that 114 dB into a playback, there are a lot of other steps along the way, and the sum of those parts — like it or not — will reduce that figure considerably. Essentially, the final dynamic range of any system is determined by the weakest component in the audio chain.
The human ear responds well to dynamics — to a degree. Listening to a widely dynamic classical piece, such as Igor Stravinsky’s “Firebird Suite” with a top orchestra in a great venue can be impressive, in terms of experiencing a widely variable range of levels, from a gentle pianissimo to a pounding fortissimo (or even ƒƒƒƒƒ). But listening to a recording of that same piece over a car stereo while driving through city traffic (or on the freeway) in a convertible will certainly yield less favorable results. And in that case, less dynamic range would be an asset.
The same applies to live sound, where beyond electronics, we have all sorts of dynamics and noise floor challenges. As an interesting aside, JJ Jenkins, one of our contributing writers, recently mixed a one-off with The Chambers Brothers. The setup and sound check went fine, then a few minutes after the doors opened, a woman came up to complain about the “loud buzzing” from the sound system. Surprised, he and the woman walked up to the P.A. speakers and heard no noise, although there was noticeable thumping and clattering coming from a large air conditioning duct. As that visible person standing out in the middle of the house, we typically get blamed for everything, but at least this time, it wasn’t audio’s fault.
While we would all like to have a punchy, dynamic show that takes the listener on an auditory thrill ride, it isn’t always possible. There is no shortage of acts in every genre who draw audiences that scream, whistle, talk, holler and sing loudly throughout a show (thankfully, texting isn’t so noisy) to the point where an ambient level — even before the P.A. kicks in — exceeding 100 dB is easily measureable. I imagine The Beatles’ first USA tour is a good example of this phenomenon.
A Little Irony
Here’s where the real irony sets in. The maximum occupational noise levels set by OSHA limits 100 dBA sound level exposure to two hours a day. And for NIOSH, the 100 dBA recommended max is less than 15 minutes of exposure per day. So theoretically, a promoter or sound provider could face liability for participating in a loud-audience performance even if the P.A. was not powered up.
Let’s hope that never happens, but maybe there is a moneymaking opportunity for someone to invent some “cone of silence” style devices that could automatically lower from the ceiling to envelope fans who are obnoxiously noisy. Perhaps something like that might make a technology debut at this month’s PLASA, LDI or AES shows. If so, I might be the person to send in a contribution to a GoFundMe campaign.
Bring on the Parnelli’s
Speaking of shows, the votes are in and the annual Parnelli Awards (sponsored by FRONT of HOUSE and PLSN) takes place on Oct. 24, during the weekend of the LDI show in Las Vegas. It’s the place to be for pros in every phase of the sound reinforcement and event production industry, so if you’re interested in attending, go to parnelliawards.com and snag a few tickets soon, as past years were complete sellouts. Besides, it’s an evening of fun, including a cocktail reception with ample opportunities for networking, the ceremony itself and the not-to-be missed Parnelli After Party. Hope to see you there!
For George Petersen’s introduction to the Oct. 2015 issue of FRONT of HOUSE magazine, go to: https://www.youtube.com/watch?v=g1ZmRegTkdw
