A-Weighted Sound Pressure Level

The human ear is generally said to be able to hear only from 20 Hz to 20 kHz. Moreover, low frequencies and very high frequencies are not perceived as being very loud, so simply measuring sound pressure regardless of frequency will result in a slight discrepancy with the human perception of loudness. Therefore, when measuring the sound pressure level, it is necessary to adjust the sound pressure level according to the frequency so that the degree of loudness is close to that of human hearing. The A-weighted sound pressure level is the result of this correction.
The following graph shows a comparison between the actual measurement in A-weighted sound pressure level and the sound pressure level measurement itself (C-weighted).