DbA Sound levels for youth gig night

[Simon Lewis]

Am I correct in thinking the weapon of choice from the HSE is LA8EQ (sp?) ie Leq a-weighted over 8 hours for the daily dose?

 

The measure is L_EP,d i.e. the A weighted Leq calculated over 8 hours. Even if the actual exposure is more or less than 8 hours, you normalise it to 8 hours.

 

Since an Leq is a time weighted average, unless the sound measured is fairly constant, the Leq is likely to be less than the instantaneous A weighted reading.

 

Is there any rule of thumb between the two?

 

You can calculate Leq from a number of steady sound pressure level measurements (SPL1, SPL2, SPLn etc.) for a known duration (t1, t2, tn etc.): In reality, these would actually be a series of short term Leqs that characterise a particular work activity.

 

L_EP,d = 10 log ((10^(SPL1/10) x t1 + 10^(SPL2/10) x t2 + 10^(SPLn/10 x tn) / 8)

 

Let's say that a sound engineer is exposed to 80dB(A) for 2 hours, 88 dB(A) for 3 hours and 55dB(A) for 3.5 hours. Even though the total time is 8.5 hours, we will calculate to an 8 hour exposure

 

 

L_EP,d = 10 log ((10^8.0 x 2 + 10^8.8 x 3 + 10^5.5 x 3.5) / 8) = 84.2 dB

 

 

TBH, I don't have any serious concerns about the levels being bandied about for this event. I rarely push the rig over about 100dB(a) and generally mix around 95dB. I'm just trying to make sure that I'm arguing for a policy which is healthy but also pragmatic

 

What I didn't put in my last post was the effect of keeping the exposure to ~94dB. Everything falls back almost within conawr:2005 ;-)

 

Hope this helps, and sorry I can't post stuff from equation editor!

 

Simon