"Don Pearce" wrote in message
...
On Thu, 4 Oct 2007 10:33:24 +0300, "Iain Churches"
wrote:

"Don Pearce" wrote in message
...

What are the numbers?

They both peak at 6276 Hz.
The difference between them is 5.6dB
At 6.276kHz the 468 is +12.2db and ARM is 6.6dB

Does anything you have say why the curves go on rising all the way to
beyond 6kHz? That is a long way past the peak of the human hearing
response, and seems a strange thing to do for a noise weighting
system.

Don. In a nut-shell, The ITU-R 468 noise weighting curve was
developed by the BBC specifically for noise measurements in
audio equipment. It is said to be better suited in this role than
"A" weighting which is more valid in the measurement of tones
as opposed to noise.


Not only that, but it all goes a very long way above zero and I'm not
too sure I buy that either.

Then the old "A" curve is the one for you:-)
It is described as "benign"

During the 1960s, it became evident that the DIN A-weighting
curve did not give results reflecting a real-world situation.
The BBC's report EL-7 in which the results from various
listening experiments using clicks and tone bursts were
published. Those being tested were then asked to compare
these with a tone of 1kHz. The scores were then compared
with noise levels measured using various weighting filters.

Based upon the work done principally it seems by the BBC,
CCIR recommendation 468-1 was published. There were
further revisions made from time to time, up to revision 4.0.
The curve remained basically unchanged, but tolerances were
specified more accurately. CCIR 468 was subsequently
adopted by the IEC (International Electrotechnical Commission)
and the ITU (International Telecommunications Union) and
became the accepted method for measuring noise in broadcast,
professional audio applications and high-fidelity.
When the CCIR was disbanded in March 1993, the
ITU took over the existing standard.

Iain