Data reduction happens all the time. The sample above requires your brain to re-construct the missing parts to make it read “can you understand me clearly.” Not too difficult.

MP3 recordings treat the audio in much the same way… they toss out as much as they can, and leave just enough pieces that your brain can fill in the gaps without too much trouble. MP3 coding can leave out 80 – 90% of the original material!

This is the reason that bit-reduced audio (mp3, aac, ogg, and others) should be used only for the final step in the audio chain. The “reduced” audio is specifically designed to be understood by human ears… not necessarily by another piece of audio editing software.

If you record an interview on your portable machine using mp3, it’s already been reduced within an inch of its life.  Then you re-inflate the audio to edit the file on your PC. When you’re done editing, if you save the file as mp3, the algorithm again tosses out as much data as possible. The problem is, it was already “reduced” as far as could be reasonably tolerated… now you want to take out more? This won’t be pretty.

Storage is cheap these days. (A 2TB – that’s 2000 Gigabytes – hard drive can be had for less than $100) You should always record new material in full linear mode (PCM, WAV, AIFF) and at least 44.1KHz, 16 bits. Keep the audio “full-size” throughout the editing process. Then play the non-reduced file on the air, if possible. This applies to music, too. Don’t play an MP3 if you have access to the CD.

If your playback system requires that the audio be stored as mp3, use the highest bit rate you can… at least 256K.

The file you play is going to be manipulated several more times before the listener ever gets to hear it. Give the audio a chance to make it through the maze with minimal battle-damage.


2 thoughts

  1. Great write-up. I record all my original material in WAV and only compress when I want to upload. MP3 is great but it has limits. Unfortunately people tend to go over the limit.

    It puts engineering concepts in ENGLISH!!
    When mp3s first came out, they were the next best thing…great way to store your music!! and play it on an mp3 player!!!
    I’ll try and remember the source when I use these phrases…

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