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General Asylum General audio topics that don't fit into specific categories. |
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In Reply to: RE: Too loud... posted by Todd A. on February 19, 2015 at 13:32:09:
I'm talking at a normal level Now for 16 seconds:Here are some measured dB levels for that 16 Seconds:
63.3dBA Leq (Equivalent Average) This is the parameter that is used for the 8 hour Average limit for the workplace at 85dBA!
Note: It takes levels averaging at 85 dB for months or years to produce hearing loss - individual's mileage may vary. This measurement also uses an A-Weighting Filter on the signal before the measurement. The A-Weight network a crude adjustment of the signal so that it may numerically be compared to how loud to humans the signal appears to be. C Weighting is another filter used on the signal. It is essentially a flat bandpass filter with -3dB points at 40Hz and 8kHz with 2nd order slopes69.7dB LZeq this is the unweighted measured average over the 16 seconds (no A-Weighting applied). This the engineering measurement in dB ref to 20 micro Pascals of the pressure variations at the microphone.
89.0dBZ Peak - this is the unweighted maximum peak level of my voice talking. think off peak as the excursion inward or outward of your eardrum (or a microphone diaphragm). The peak to LEQ ratio expressed in dB is called the crest factor of the signal. Note that in this case - My Voice talking - the crest factor is almost 20dB. With voice or music this is a reasonable crest factor. In modern recordings you usually find the level compressed to between 10 to 13dB (sometimes even less). The effect of this compression is to make the production seem louder - and louder is better.
This level compression also makes it "safer" to play back on lower quality playback equipment a 20dB variation is a 10 to 1 ratio where a 10dB variaton is only 3.16:1. A 2.83 Volt signal from your amplifier might produce 85dB at your listening chair (pretty loud - but nowhere near live concert levels. - that same amplifier has to be able to pass 28.3 volts unclipped for a 20dB crest factor signal vs. only 9 volts or so for a 10dB crest factor.
Another way to think about this is that your power amplifier - when playing back most signals is wasting a lot of power capability - or is clipping a bit depending on the signal or playback level.
73.7dB LAFMax or 76.9dB LZFMax is the RMS averaged signal with an exponential RMS averaging time of 1/4 second ("F" is for "Fast".) This corresponds well to the loudness of fluctuating signals and is pretty close the dynamic behavior of the famous VU meter used in recording devices. Cheap sound level meters (not the expensive one I used) allow you to select FAST or Slow, and maybe Peak.) This one measures just about everything automatically.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius
Edits: 02/20/15
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Follow Ups
- One dB is not the same as another dB - BigguyinATL 14:42:20 02/19/15 (1)
- Thank you... - Todd A. 15:13:27 02/19/15 (0)
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