"Don Pearce" wrote in message
...

Iain, I've just looked at the curves, and I don't see the ARM curve
being 1kHz to the right of the 468 - it looks like identical
frequencies but 6dB lower to me. Hard to see from the graphs, but they
appear to peak at the same frequency.

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

It looks as if the Dolby recommendation for
the shift upwards of 1kHz was not implemented
I still have a lot of reading to do.

Comparison of noise levels using the different weighting
options is interesting.

Iain