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Specific DB Scales

Since we so often rescale our signals to suit various needs (avoiding overflow, reducing quantization noise, making a nicer plot, etc.), there seems to be little point in worrying about what the dB reference is--we simply choose it implicitly when we rescale to obtain signal values in the range we want to see. In particular, dB relative to full scale ( $ 20\log_{10}(A/A_{\mbox{\small max}})$ ), abbreviated dBFS, is perhaps the most commonly used case in the digital audio world. Thus, 0 dBFS means maximum amplitude, and typical amplitude levels are negative in dBFS. In addition, there are a few specific dB scales that are worth knowing about, mostly for historical reasons, such as to understand VU meters in vintage audio gear and virtual analog plugins.



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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 © 2014-04-21 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University
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