By Brad Madix
Ed. Note: We sent the linked article to a couple of A-list engineers who sent us some great stuff. Thanks to Brad Madix for making sure I did not make a total idiot out of myself by confusing the 6 dB number that represents a doubling of actual SPL with the 10 dB number that represents a doubling of perceived volume. Here is more of what he had to say on the subject.
Hi, Bill. Very interesting article!
Regarding your article, I was interested in the OSHA link, as it conflicts slightly with what I’ve seen from them before, but the basic formula remains the same. I’ve written about this before, somewhere, I don’t remember where. Anything 85dB or below is fine regardless of exposure time. At five dB increments, exposure time is limited, as the table shows, with a limit of 105 dBA of 1 hour. The CDC has a table also which is somewhat more limiting (exposure times are halved at 3dB increments). I’ve tried to split the difference, myself. I use 4dB increments, but really this is just me walking that fine line between two huge bureaucracies.
I would hasten to point out that both of these tables are designed for “continuous noise” and do not apply very well to music. In fact, I often do very long LEQs of Rush shows, and we are rarely over 100dBA, and we were usually closer to 97-98dBA. However, these are three hour averages. At any given moment, we are likely to be over 105dBA, but we are probably more often under 95dBA. I’m willing to bet that if engineers did A-weighted LEQs across their entire shows, they’d be surprised at how quiet they actually are. Not that they’e especially quiet, just that 2 hours of continuous 102 dBA is very, very loud.
One way that gear may be helping things is that we are getting better and better at spreading SPL evenly throughout venues. So while it still might be 102dBA at FOH, it’s now closer to 102dBA up by the stage (and you’re less likely to be getting killed by subs, more of which are likely flown) and it’s probably more like 102dBA past FOH as well, as PA’s are zoned so that we can throw further.
Another story regarding politics: I had a manager complain to the PM on a tour that we needed more PA because the people at the top of the arena weren’t dancing. Management figured that had to be because it wasn’t loud enough. To be fair, it was a very large building (AA arena in Phoenix), but it was plenty loud, trust me. We picked up delays in LA (we were going to anyway, for Staples) and kept them for the rest of the tour. The additional gear required the addition of a truck to the tour along with an additional sound technician. The additional sound tech required the addition of a bus, so suddenly all of the busses went from totally full to seven or eight each, after reshuffling. Everyone went from “coffin” to “condo” in touring lexicon.
I initially argued against the extra PA (what was I thinking?) It just struck me as unnecessary. Then I decided that I didn’t want to be the first FOH guy ever to argue against more PA… plus I got a bigger bunk. While I was batting it around, however, I decided to call the Promoter Rep in Phoenix and ask him if we got any complaints the night we were there. As it turns out, there were about a dozen-and-a-half… All that it was too loud!
It turned out that the manager who decided we had to have more PA never actually went up to the 400 level where she thought people weren’t dancing enough. I also later found out the manager had a hearing problem. Anyway, we got the PA, and flew it every day. Every day. Whether we needed it or not.
For what it’s worth.