Matt here again. I took an mp3 listening test here a while ago. The audio test was between an MP3 of 320kb/s vs. MP3 of 128kb/s. A number of people commented that a test between a pure wav. file against a 320kb/s mp3 would be more useful.
So I went into my vault and pulled out a 24bit wav file with plenty of harmonic content – all sorts of broadband sound just begging to be handled with kid gloves. Then I shot it through my iTunes mp3 encoder and yanked out a 320kb/s version. The mp3 is only 25% the size as the wav, but is there a sonic trade off?
Which file is the mp3, and which is the wav?
It’s hard to disguise the files using this format.
In order that you don’t cheat (by looking at the file names or file load times),
have a friend play these for you in random and see if you can hear a difference.
*** DO NO READ BELOW UNTIL AFTER YOU TRY THE TEST ***
I’ve attached a frequency chart and a null test.
The frequency charts are identical, but as you can see the 2nd frequency chart (representing the mp3) has a steeper roll off after 16khz. The null test reveals the sonic difference between the two files. Not all of this represents loss of sound – it represents change in sound. The mp3 quantizes differently, which is not a loss of sound – just a micro-auditory restructuring of sound. The loss is broadband information which is harder to perceive than designated frequency information. However, if you notice the biggest difference exists where the snare drum is hitting – and it’s no coincidence that snare drums contain the highest content of broadband sound.
Frequency Chart for .WAV file
Frequency Chart for .MP3 file
Like the song in the sample?
It’s called Memorabilia by Mechanical Minds