I took some mp3 files of people talk with noise in the background and then removed the background noise using online voice seperator tools (such as https://vocalremover.org/). I was surprised to find out that the size of my files increased (about 5 times bigger).

Why did it happen? Is there another audio format or background noise removing method that would reduce my file size when removing the background noise?

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    $\begingroup$ What file format were the output files? $\endgroup$ Dec 29, 2020 at 8:31
  • $\begingroup$ @OlliNiemitalo mp3 $\endgroup$ Dec 29, 2020 at 8:34
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    $\begingroup$ What are the bitrates of the input and what are the bitrates of the output mp3 files? $\endgroup$ Dec 29, 2020 at 8:36
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    $\begingroup$ @OlliNiemitalo Yes, I think it increases the bit rate. Thanks, now I understand it better. $\endgroup$ Dec 29, 2020 at 9:03

1 Answer 1


This is has nothing to do with the noise removal process but with your encoding. In order to do any type of processing with an encoded audio file you need to

  1. Decode the input file to PCM
  2. Process PCM data
  3. Encode the PCM into the desired output format

Please note that steps and 1 and 3 are completely independent. The decode is determined by the input file format and the encode by the desired output file format. If you want those to be the same, you need to capture all encoding parameters from the input file and pass them to the encoding process.

In your case, you are probably using a different bitrate for input and output.

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    $\begingroup$ Even with a correct bitrate, it's not going to be perfect quality. Taking a lossy input and outputting to a lossy format introduces generation loss. Such loss can be avoided if your source files are all lossless and you compress at the very end, or if you don't [lossily] re-compress audio that was previously lossily compressed. $\endgroup$ Dec 29, 2020 at 17:40

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