A計權

計權網路一般有A、B、C三種。A計權聲級是模擬人耳對55dB以下低強度噪聲的頻率特性，B計權聲級是模擬55dB到85dB的中等強度噪聲的頻率特性，C計權聲級是模擬高強度噪聲的頻率特性。三者的主要差別是對噪聲低頻成分的衰減程度，A衰減最多，B次之，C最少。A計權聲級由於其特性曲線接近於人耳的聽感特性，因此是目前世界上噪聲測量中套用最廣泛的一種，B、C已逐漸不用。

從聲級計上得出的噪聲級讀數，必須註明測量條件，如單位為dB，且使用的是A計權網路，則應記為dB(A)。

A frequency-response adjustment of a sound level meter that makes ITS reading conform to human response. The sensitivity of the human ear is frequency dependent. At low and high frequencies, the ear is not very sensitive, but between 500 Hz and 6 kHz the ear is very sensitive. The A-weighting filter is a broadband filter that covers the interval from 20 Hz to 20 kHz. The shape of the A-weighting curve approximates the frequency sensitivity of the human ear. So the A-weighted value of a noise source is an approximation to how the human ear perceives the noise.