I thought mp3 encoding doesn't have a uniform sampling rate, how then sox --i shows sampling rate field for mp3s? I see 44100 sampling rate for an mp3 file.

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    This is a sound design forum, i downvoted your question because it's off topic and can by answerred easily by a google/wikipedia search. – Arnoud Traa Mar 15 '14 at 7:50
  • @ArnoudTraa then the URL should have been sound-design.SE no? Why call it sound.SE? – user13107 Mar 15 '14 at 7:52
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    Relax, i didn't create that name. This used to be called 'social sound design' not my decision to change that. But did you look at wikipedia for samplerate and mp3 bitrates? – Arnoud Traa Mar 15 '14 at 8:30
  • Oh btw i see now that the site actually does say Sound Design :) It's just not in the URL. – Arnoud Traa Mar 15 '14 at 11:04
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    I'm voting to close this question as off-topic because it's not useful or a good fit. – user9881 Oct 7 '16 at 4:47

Simply, your understanding is incorrect. MP3 does use a uniform sampling rate, it reduces resolution of the sound in areas where the resolution is unneeded so that it fits a simpler pattern that can be more efficiently compressed, but it decodes to a fixed sample rate.

As EMV was kind enough to point out, you may be thinking of the bitrate. The bit rate is the amount of data that it takes to encode those samples. Since resolution is selectively dropped, the amount of data required to store each sample is variable and thus the actual data rate will vary, even though the sampling frequency itself does not.

I suggest the Wikipedia page on MP3 for further reading.

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    To add to that: you're maybe confusing sample rate (constant) with bitrate (not necessarily constant: there are cbr and vbr mp3 files). – EMV Mar 17 '14 at 14:16
  • @EMV - great thought on why they may be getting confused. – AJ Henderson Mar 17 '14 at 14:24

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