On 2007-10-04, Don Pearce wrote:
Just done something similar on my DAW. I've also created an A curve.
Made a chunk of white noise and compared the average noise levels.

Flat -19.44dB
A wt -21.7dB
468 -12.59dB

So that is a 19dB difference. I only eyeballed the filters, so I could
be a bit out. This is all a bit odd. I can see there being differences
between two subjective curves purporting to be of the same thing, but
19dB? Something smells nasty.

[Noting Don's correction from 19 dB to 9 dB]. May I ask if this
comparison is relevant?

Weighting curves are relative. AFAICS you just can't compare the absolute
audibility of A-weighted noise with ITU-R 486-weighted noise from the
same source. You can only compare weighted figures with the same type
of weighting.

AFAICS, for each weighting the absolute threshold of audibility may be
rather different. What you may get from comparing 468-weighted noise
figures is a more valid comparison WRT human audibility of noise than
from comparing A-weighted noise figures.

--
John Phillips