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# what is the significance of the number in front of dB when using audio extraction tools?

Posted on 2010-04-10
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Hi Everyone;

Lately, I have been using CDex with great success in ripping some music cd's to mp3.  While I understand the majority of what I am looking at, one thing which is not clear to me relates to dB.  From what I understand, dB is a measure of sound waves if I am not mistaken.  I noticed in the area of CDex called Peak Value, there is a number like -2.86dB=71%, the second track might be 0.00dB=100%, the third track might be -2.38dB=76%, and so forth.  Basically, each track which goes through the extraction process has a dB value and a percentage.

With what has been presented here,  I am interested in any interpretations which can be given for these numbers.  While I am sure this is just trivial, it still would be nice to have an understanding of this.  Perhaps it is some type of interference ratio which gives an indication of the audio quality of each track.  Of course, this point is mere speculation on my part.

At any rate, any shared input to this question will be greatly appreciated.

Thank you.

George
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Question by:GMartin
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knightrd earned 1000 total points
ID: 30346995
It's a logarithmic scale to describe how loud something is. It's nothing really to do with audio quality. You might want to play around with MP3Gain if you are concerned about making sure that your songs sound equally loud:

http://mp3gain.sourceforge.net/

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rugbyguitargod earned 1000 total points
ID: 30350289
It would seem to me (being an avid user of music recording software) that it is basically analyzing each individual track on the CD and telling you the loudness (in dB) of that particular track.

The interference ratio that you are talking about is Eb/N0, or in its more simple form, Signal-to-Noise-Ratio (SNR). very simply put, it is described in this example: for every 128 KB of total audio, there are 10.6KB of noise or interference; giving you a signal (128 KB) to noise (10.6 KB) ratio of 12, which isn't bad at all.

sorry for going so far into detail. hope this helps you understand the concept a little bit better.
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ID: 30356524
Hi Everyone;

Thanks so much for the shared input.  After reviewing everyone's thoughts on this matter, I do have one followup question to this thread.  If I have a Track 1 with a loudness index of -2.86dB and Track 2 with a loudness index of -2.38dB, which would be loudest?  Would it be the measurement which approaches closest to 0 or -2.38dB?  And, what would the interpretation be for a track with a value of 0.00dB?

George
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rugbyguitargod earned 1000 total points
ID: 30429239
the value that is closer to 0 is the loudest; this is why you see your percentage go up when the number gets closer to 0 dB.
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ID: 30489090
Hi Everyone;

Thanks so much for the rich detail given to this question.  Everything mentioned here certainly makes sense and clears up my confusion and original misconceptions regarding the dB scale.  Everyone did a great job breaking this down for me.

Many thanks once again.

George
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