DBA (A-Weighted DB)

The so-called A-weighted dB scale (abbreviated dBA) is based on the Fletcher-Munson equal-loudness curve for an SPL of 40 phons.^F.4 Thus, a dBA weighting assumes a fairly quiet pure tone. Despite this assumption, the dBA weighting is often used as an approximate equal loudness adjustment for measured spectra.

An analog filter transfer function that can be used to implement an approximate A-weighting is given by^F.5

where normalizes the gain to unity at 1 kHz.

The ITU-R 468 noise weighting^F.6is said to perform better for measuring noise in audio systems.

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About the Author: Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.