What is the difference between rms and din power?

The CCIR curve differs greatly from A-weighting in the 5 to 8 kHz region where it peaks to +12.2 dB at 6.3 kHz, the region in which we appear to be extremely sensitive to noise. While it has been said (incorrectly) that the difference is due to a requirement for assessing noise intrusiveness in the presence of programme material, rather than just loudness, the BBC report makes clear the fact that this was not the basis of the experiments. The real reason for the difference probably relates to the way in which our ears analyse sounds in terms of spectral content along the cochlea. This behaves like a set of closely spaced filters with a roughly constant Q factor, that is, bandwidths proportional to their centre frequencies. High frequency hair cells would therefore be sensitive to a greater proportion of the total energy in noise than low frequency hair cells. Though hair-cell responses are not exactly constant Q, and matters are further complicated by the way in which the brain integrates adjacent hair-cell outputs, the resultant effect appears roughly as a tilt centred on 1 kHz imposed on the A-weighting.