dB(A)
dB of sound volume in relation to 20 micropascal weighted, simulating human ear sensitivity at 40 phon level.
Note 1: 20 micropascal is the human hearing threshold, i.e., 0 dB(A).
Note 2: Sound volumes louder than dB(A) are represented by a graduated scale: dB(B), dB(C), and dB(D).
Note 3: This scale is widely used in occupational safety and hearing protection measurements.