A-weighing of sound

The sensitivity of the human ear is not the same for all frequencies. The highest sensitivity is obtained for frequencies of 1000 to 6000 Hz. Higher and lower tones are perceived less well. Even sounds with the same energy are perceived less loud for high and low ranges.

A sound measuring instrument registers low frequency sounds (for instance 100 Hz) equally loud as high frequency sounds (for instance 1000 Hz). Therefore, in sound measurements, an electronic filter is used which weakens the sound the same way as human hearing. At 1000 Hz no correction is implemented, in contrast to higher and lower frequencies. This correction is called the A-weighing ( B- weighing, C- weighing etc. are rarely used).

The unit dBA is used to indicate that the sound power level has been corrected for the sensitivity of the human ear.