A-Weighting Correction Calculator
A-weighting converts an unweighted sound pressure level (dB) at a specific frequency to the A-weighted equivalent (dBA) by applying a frequency-dependent correction. The IEC 61672-1 standard defines the A-weighting transfer function analytically. At 1,000 Hz, the correction is 0 dB. At 100 Hz, it is approximately -19.1 dB, meaning a 100 Hz tone at 70 dB SPL sounds as loud as a 1 kHz tone at about 51 dB. This calculator applies the analytical IEC formula to give the correction for any input frequency.
A-weighting formula (IEC 61672-1)
R_A(f) = (12194² f&sup4;) / [(f²+20.6²)(f²+12194²) √((f²+107.7²)(f²+737.9²))]
A(f) = 20 log10(R_A(f)) + 2.00 dB
The +2.00 dB normalises the curve to 0 dB at 1,000 Hz. The A-weighted level is the unweighted dB plus A(f).
Key A-weighting values from IEC 61672-1
- 100 Hz: -19.1 dB
- 250 Hz: -8.6 dB
- 500 Hz: -3.2 dB
- 1,000 Hz: 0.0 dB (reference)
- 2,000 Hz: +1.2 dB
- 4,000 Hz: +1.0 dB
- 8,000 Hz: -1.1 dB
Frequently asked questions
What is A-weighting?
A-weighting is a standardized frequency filter that adjusts sound level measurements to approximate human hearing sensitivity. The human ear is most sensitive around 1,000 to 4,000 Hz and less sensitive at low and very high frequencies. A-weighting applies corrections (in dB) at each frequency to produce dBA levels.
What are the A-weighting correction values?
Selected values from IEC 61672: 31.5 Hz = -39.4 dB; 63 Hz = -26.2 dB; 125 Hz = -16.1 dB; 250 Hz = -8.6 dB; 500 Hz = -3.2 dB; 1,000 Hz = 0.0 dB; 2,000 Hz = +1.2 dB; 4,000 Hz = +1.0 dB; 8,000 Hz = -1.1 dB; 16,000 Hz = -6.6 dB.
Why is dBA used for occupational noise standards?
Because dBA correlates better with hearing damage risk than unweighted dB. OSHA and NIOSH both specify exposure limits in dBA because the frequency weighting reflects the frequencies at which noise is most damaging to the cochlea.
What is the difference between dBA, dBB, and dBC?
A-weighting (dBA) mimics the human ear at moderate levels. B-weighting (dBB) is rarely used today. C-weighting (dBC) applies minimal correction and is used for peak measurements and loud impulsive sounds. D-weighting is used for aircraft noise.
How is the A-weighting correction calculated analytically?
The IEC 61672-1 standard defines A-weighting by the formula R_A(f) = (12194^2 f^4) / ((f^2+20.6^2)(f^2+12194^2) sqrt((f^2+107.7^2)(f^2+737.9^2))). The A-weighting value in dB is 20 log10(R_A(f)) + 2.00 to normalize to 0 dB at 1 kHz.
Official sources
- IEC 61672-1: Electroacoustics, Sound Level Meters (defines A-weighting).
- OSHA: Occupational Noise Exposure.
- NIST: National Institute of Standards and Technology.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.