Today’s WFTD was brought on by today’s Tech Tip question from FC in NC.
“When I do live sound gigs I find that as the night wears on I seem to have to turn the volume up more and more to keep the energy level up and to just keep the volume the same. Sometimes people say it gets too loud, but I don’t hear it that way. Are my ears lying?”
YES, but there is more to it than that. There are actually many, many factors at work here. One of the more significant problems is a phenomenon known as Temporary Threshold Shift, which are your ears effectively turning themselves down for protection. All soundmen face this problem and it is very dangerous to your long-term hearing. A good way to help prevent volume runaway (as I call it) is to mix with earplugs and carry a SPL meter. I know, I know, ear plugs screw up the sound, you say. Well, there are actually some custom ones you can get that keep things pretty well in order (though they are not perfect). What I’ve always done, however, is use regular cheap ones and check the sound by pulling them out every few minutes. It’s amazing how fast you can learn to adapt to this (the brain is an amazing instrument). In concert with a SPL meter for objective measurement this works great. If you absolutely refuse to wear ear protection at least use a SPL meter to keep track of the volume.
There are other factors that may cause you to turn up the volume over the course of the night. Alcohol has the same affect on your hearing senses as it does the rest of you. Just say no to that. When I was playing I would have instantly fired any sound engineer drinking on the job. This is totally unprofessional and, more importantly, unsafe.
Sometimes turning one or two instruments up in a mix (for a perfectly valid reason) will result in some other instruments being covered up a bit. The solution is not to come behind yourself and turn these other instruments up too. You need to keep track of where you are in the mix and if you turn something up you should remember to turn it back down when it is no longer the focus. I can’t tell you how many times I’ve seen soundmen end up at the end of a night with all of the individual faders on their board almost all the way up while the master fader is relatively low. That’s a clear sign of a soundman that let it get away from him. Even if you can’t hear what you are doing this should at least be a visual clue. It’s easier said then done, but try not to let the instruments fight each other. EQ them so each has its place. Sometimes you can turn up a guitar for a solo by simply adding a little upper midrange to the EQ and not touching the volume at all. You just have to remember to take it back out once the solo is complete. Keep track of where you are and try not to mix by always turning something up. Sometimes it is appropriate to turn three things down instead.
Sometimes you really do have to turn up the volume over the course of a night just to keep it the same. As a room fills up with people, or dancers pack onto the dance floor (in front of the PA), they will absorb sound. If you intend to keep the volume close to the same in the back of the room you will have to turn it up some to compensate for this. It also sometimes becomes necessary to add a little top end (high frequencies) to the house EQ. As the speakers in the PA heat up their impedance will rise a little bit. This makes them less sensitive and will result in more power needing to be applied to reach the same volume, at which point they heat up more, and so on…
There are other factors that contribute to this phenomenon, but your own ears are usually the big variable. Use objective measuring techniques (SPL meter) and trust the measurement.