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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.8 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 byF.9

$\displaystyle H_A(s)
= \frac{k_A \cdot s^4}{(s+129.4)^2 (s+676.7) (s+4636) (s+76655)^2}
$

where $ k_A \approx 7.39705\times 10^9$ normalizes the gain to unity at 1 kHz.

The ITU-R 468 noise weightingF.10is said to perform better for measuring noise in audio systems.


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``Mathematics of the Discrete Fourier Transform (DFT), with Audio Applications --- Second Edition'', by Julius O. Smith III, W3K Publishing, 2007, ISBN 978-0-9745607-4-8.
Copyright © 2014-04-06 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University
CCRMA