Re: Line array for 1500 cap venue
126dBC is inappropriate and irresponsible as you have damaged peoples ears and thats even too loud for people with hearing protection.
The 126dB is C-weighted SPL, a difference of about 25dB at 63Hz and 16dB at 125Hz from A-weighting, thus the 13dB to 18dB lower A-weighted levels. That's also the peak levels with the average levels being lower and I'm guessing those are more a "we were typically around 117dBC/104dBA during songs" than an actual TWA, LEQ or other statistically derived average.
Since A-weighting is actually based on human response at normal speech levels and not at concert levels, someone who understands SPL weighting can often play around with the frequency content to get greater perceived loudness for a given overall A-weighted SPL level. Conversely, a system optimized for speech intelligibility may exhibit higher A-weighted SPL levels than might seem associated with the perceived loudness.
Of course, the punters in the front rows are absorbing another 10+ dB over the position of your meter.
Unfortunately, if you are not the only act, and you have also done a sound check, and been around a loud load in, you have already subjected yourself and the audience to levels that exceed OSHA's exposure level, and around 10 dB louder than the NIOSH levels.
Exceeding those levels statistically cause hearing damage.
With around a 50 dB noise induced hearing loss at 4000 Hz, I'm one of those fucking statistics.
All about "good n' loud".
dBA Slow
OSHA (1998)
90 for 8 hours
92 for 6 hours
95 for 4 hours
97 for 3 hours
100 for 2 hours
102 for 1.5 hours
105 for 1 hour
110 for 1/2 hour
115 for 1/4 hour
NIOSH (1998)
85 for 8 hours
90 for 2.5 hours
95 for 47 minutes
100 for 15 minutes
There are many misunderstandings regarding the noise component of OSHA and NIOSH and much of that seems to stem from the fact that OSHA and NIOSH both address long term noise exposure in the work place, i.e. repeated exposure by employees over multiple 8 hour periods. NIOSH and OSHA don't address anything other the exposure over an 8 hour period and the charts presented are actually expressing how to relate shorter exposures during that 8 hour period to the allowable 8 hour 'dose'. In other words to be compliant you have to meet not only the criteria for any directly relevant shorter time period but also all of the guidelines for any longer periods as well. Thus that chart is not saying that a 105dBA TWA for 1 hour is acceptable but rather that it is allowable only if you also meet a 102dBA TWA for 1-1/2 hours, a 100dBA for 2 hours, 97dBA for a 3 hour period, 95dBA for 4 hours, 92dBA for 6 hours and a 90dBA TWA for an 8 hour period, all of which relate to the 90dBA, 8 hour noise exposure 'dose' that is allowed.
OSHA and NIOSH also do not actually limit the source noise levels, only the resulting exposure. That could mean reducing the source levels but it can also involve active measures such as hearing protection or administrative measures such as limiting the time one is exposed. For employees it is quite common to have source levels well over those allowed and to employ active and/or administrative measures to reduce their exposure, that is a bit more challenging to apply to an audience of non-employees that can come and go as they want and can use noise reduction measures or not as they please.
Also often overlooked is that OSHA actually has a lower SPL level criteria that does not require active measures but that does entail having to establish a hearing monitoring program. If I recall correctly that relates to a 85dBA 8 hour dose.
The point is that while perhaps better than nothing, it is really difficult to directly apply OSHA or NIOSH to concerts or other events except in relation to the exposure of employees over an 8 hour time period. And the related information is often misunderstood and misapplied in trying to do so. Of course the irony in even trying to relate OSHA and NIOSH to concerts is that they address noise, which is unwanted or undesired sound. That may be an accurate application in some cases but some may not like that their performance being considered noise.