Which settings should I use on the REW SPL Meter to understand danger levels to my ears?

2012 Views 4 Replies 3 Participants Last post by JohnM, Oct 7, 2015

mstang1988

Discussion Starter · Oct 6, 2015

I have REW running on my Mac (OSX Yosemite). I have a umik1. For whatever reason LZpeak never goes above 100.6db. I'll hit it at -25db or 0db (with my ears plugged). Should I be using LAFmax? Even if I crank up the volume to 0db I still don't hit > 100.6db for LAFmax which I would expect adding 20db to the graph below. Is there a limit here in REW or the UMIK?

Full system details 5.1:
Anthem MRX-510
Rotel 1091 Monoblocks for mains (500w RMS at 8ohm)
Rotel RB-1085 5 Channel for center and surrounds (100w RMS at 8ohm)
Infinity PS-12 Subwoofer (300W RMS)
RTi12 Mains (90db sensitivity)
CSi5 Center
RTi6 Surrounds

Seating: 11ft from mains and center, sub
Surrounds: 5ft from seating position
Room: 13'9"x19'x9'
Treatments: 6 rockwool 80 panels on back wall (two in the corners as bass traps).

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Wayne A. Pflughaupt

· #2 · Oct 7, 2015

I’m a bit confused here. The title to your thread indicates that you want to know at what point sound pressure levels become a danger. But the post indicates that you’re wondering why you can’t get a test signal to play louder than 100.6 dB. :huh:

Regards,
Wayne

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JohnM

· #3 · Oct 7, 2015

The maximum input level the UMIK can measure depends on the input volume setting. If the UMIK is from the last couple of years, the maximum input with the input volume set to 1.0 is about 100 dB, above that the mic will clip. When input volume is 1.0 the mic actually applies 24 dB of internal gain, if the input volume is lowered to the point it applies 0 dB of gain the maximum input level would be about 124 dB. The 0 dB setting on a Windows 8.1 machine is 0.52 or 52%, but you can see the setting more easily by setting the input volume control to show dB instead of percent by right clicking on the volume control on the Levels tab of the input properties.

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mstang1988

Discussion Starter · #4 · Oct 7, 2015

Wayne A. Pflughaupt said:
I’m a bit confused here. The title to your thread indicates that you want to know at what point sound pressure levels become a danger. But the post indicates that you’re wondering why you can’t get a test signal to play louder than 100.6 dB. :huh:

Regards,
Wayne

I should have been more clear but typing late at night when I typed it I didn't make a lot of sense. Ultimately I have seen charts for safe hearing levels but two things are preventing me from comparing my listening levels to that data:

The value(s) to use when comparing to exposure charts
The levels on my mic seemed like they may not be working correctly due to the 100.6db issue so I wanted to make sure I was using accurate data

The post above solves the mic question, now the further question is which values from REW to use when comparing to exposure charts.

Is it peak, max, etc.

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JohnM

· #5 · Oct 7, 2015

The safe levels depend on how long the exposure lasts, a level that can be tolerated without harm for a short time could cause permanent damage if it continued for a longer time. The 'equivalent sound level' takes account of the varying levels of sound over the measurement period to provide a number that takes account of the overall 'dose' of sound, so typically LAeq would be the figure to monitor. Over an 8 hour period the maximum Leq figure for the UK is 85 dBA, for example. This paper from Bruel and Kjaer explains the various terms and their relevance.

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