A-Weighting

A-weighting is a filtering or a filter function inserted in the signal chain. It applies in particular to the measurement of acoustic noise at the workplace and the environment. However, it also applies to the measurement of noise in microphones. To some degree, the A-weighting filter mimics the frequency response of the human ear at lower levels (the 30 phon equal loudness curve) (see Equal Loudness Contour). B- and C-weighting curves belong to this family of curves; however, these were developed to be used at higher levels. A-weighting is specified in IEC 60 651, but references are also made in other standards like ANSI S1.4-1981. Measurements performed with A-filters are often described with an "A" in parentheses, for example, xx dB(A) or with an "A" as an index, LA = xx dB.