reducing the size of an MP3 file

I have an recording of a 2-hour talk show radio program saved in the MP3 format. It’s about 103MB and I want to reduce the size so I could readily share this with friends and family members. It’s recorded in stereo and 32 bit quality. Someone suggested converting this to monaural (mono) and/or reducing the sampling rate. How do I go about this using Audacity? You see, I need to get this out ASAP. Thank you for your suggestions.

Audacity’s default MP3 bitrate is set to 128 - this is generally rgarded as the lowest acceptable bitrate for music.

For spoken work you can usually go much lower - 64 or even 32 without creating bubbly digital artifacts from the compression.

To reset the bitrate in 1.2 go to Edit>Preferences >File Formats>MP3 Export Setup - in 1.3 it can be reset more dynamically on export (use the Options button on MP3 exports)

Experiment …


To Export as a mono mp3, mix down the track to mono before you export. This will make the mp3 about half the size of a stereo mp3.

To convert to mono (Audacity 1.3.4):
If your tracks have been “Normalised” or Amplified to 0 dB, then you will need to reduce the level a little. Use the volume slider in the box at the left hand side of the track and drag it a little to the left (-6 dB should do).
Now click on the little down pointing arrow next to the track name, and from the drop down menu select “Split Stereo Track”.
For each of the split tracks, click on the arrow and select “mono”
Now press “Ctrl A” to select all and from the “Tracks” menu, select “Mix and Render”.

If the recording is just one voice (a mono recording on 2 tracks), it is even easier - just split the stereo track as described above, set one of them to mono, and delete the other one.

to: waxcylinder and stevethefiddle
Thank you, sirs. I have followed your suggestions and I’ve reduced the size of the file to 50% - about 53MB. I’m just about to break it up into ‘emailable’ pieces.

If you are doing that with Audacity, use the original uncompressed version. If you do it by opening the mp3 than exporting bits of it, you will be decoding and re-encoding which will reduce the sound quality further.

If you must do it from the mp3 file, use an mp3 splitter program that does not need to decode the mp3 first.