What is "Frequency Weighting"?

Frequency Weighting

Modification of the frequency spectrum of a signal employing a filter with a characteristical frequency-dependent response. Examples of these responses are, e.g., IEC-A, (applies to noise measurements, of for instance self-noise in microphones), IEC-B, IEC-C, or IEC-D, CCIR/ITU, or for instance RLB (Revised Low-frequency B-weighting).

The basic aim is to emulate the response of the human ear.