From mboxrd@z Thu Jan 1 00:00:00 1970 From: Werner Van Belle Subject: Re: wrong decibel data? Date: Sat, 10 Apr 2010 08:56:55 +0200 Message-ID: <4BC02137.6000207@yellowcouch.org> References: <4BBF5F81.1010205@yellowcouch.org> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1178790572620976223==" Return-path: Received: from sigtrans.org (sigtrans.org [213.239.213.249]) by alsa0.perex.cz (Postfix) with ESMTP id 5A150103803 for ; Sat, 10 Apr 2010 08:57:52 +0200 (CEST) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: Raymond Yau Cc: ALSA Development Mailing List List-Id: alsa-devel@alsa-project.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============1178790572620976223== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig6D1C31D2D470FBFC8C891156" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig6D1C31D2D470FBFC8C891156 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Raymond Yau wrote: >> Yes about that. I always wondered how they come up with 96dB ? >> >> A perceived doubling of volume is normally assumed to be +3dB, >> (log_10(2)=3D0.3) which means that if you have 16 bit audio you have 1= 6 >> 'doublings', or in essence only 48 dB. Even worse, since the last bit = is >> a sign bit, you essentially can only achieve a dynamic range of 45dB != >> >> Now, I know this is off topic, but I never heard any good explanation >> why CD audio is suddenly 45 dB ? If anybody knows, please share your >> thoughts ! >> =20 > http://en.wikipedia.org/wiki/Decibel > > When referring to measurements of amplitude it is usual to consider the= > ratio of the squares of *A*1 (measured amplitude) and *A*0 (reference > amplitude). This is because in most applications power is proportional = to > the square of amplitude, > > in electrical circuit , dissipated power is typically proportional to t= he > square of voltage or current > =20 Okay, that would then only make for a factor two. Instead of 45dB one gets 90dB, this is still not 96dB as ordinarily claimed ? Wkr, Werner,- --=20 http://werner.yellowcouch.org/ --------------enig6D1C31D2D470FBFC8C891156 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkvAIToACgkQ2TDF0fTmy3WvlQCfQXoObYrSe0WAdZbryQGgMqCO uzsAn1sEWjEnRgiyfvtexuX1N9AsgaeN =GDwf -----END PGP SIGNATURE----- --------------enig6D1C31D2D470FBFC8C891156-- --===============1178790572620976223== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel --===============1178790572620976223==--