On Mon, 15 Oct 2007 08:11:09 -0400, "Arny Krueger"
wrote:


"Iain Churches" wrote in message
hti.fi...
My thanks to all those, both on and off list, who
provided useful info on the noise weighting curves.

The two ITU curves are similar but
ITU-R ARM is a later Dolby Labs
proposal which moves the whole curve
1kHz to the right.

Thanks also to my pal Richard in the UK,
I now have a chart in Excel showing all three
IEC curves, A,B and C, plus the two ITU curves.

http://www.kolumbus.fi/iain.churches...se/ABC+ITU.jpg

Comparison is interesting. One can also see why
the old IEC "A" weighted curve is still popular:-)

Do bear in mind what these curves should be approximating. They should be
approximating the appropriate Fletcher-Munson curve for the SPL being
listened to.


Is that true? The F-M curve is for the threshold of audibility and
equivalent loudness for tones on their own at various frequencies. A
noise weighting curve is designed to weight the equivalent
contribution of each frequency to a broad agglomeration. I am not
convinced that these two amount to the same thing.

Do you know of any work that has examined the similarities or
differences between these two?

d

--
Pearce Consulting
http://www.pearce.uk.com