Mp3 adds... .WHAT?

So I was reading this article (actually, someone's comment) on what converting from a lossless codec to mp3 does to your sound. I wanted to test the hypothesis: What does mp3 add (or remove) from the fundamental lossless recording?

I took my own song, "Rain", and put both the WAV and MP3 in Audacity. Here's how it looked:

    nothing in the top one, but some strange compression in the bottom one...

From there, I uploaded it to Sound Cloud. Here's what I got:
https://soundcloud.com/davdud101/rain-mp3-analysis
    notice how all you hear is strange noise from the drumkit and vox

So what say you? Is this a major degradation of the sound quality?

It depends on a few factors too such as the bit rate in mp3 encoding. Taking the bit rate up to 256 or 320 KBits/sec will give you a better sound too. You don't want to mp3 encode a very heavily mastered wave file either that is slammin right up to -0.1 dB FS. You almost need to master slightly differently or at least limit to say -1 dB FS instead. There are a few techniques to getting a good mp3 version of your mix. Not all mp3 encoders are created equal either. 

But get into AAC encoding instead here:

http://en.wikipedia.org/wiki/Advanced_Audio_Coding

The successor to mp3. It is already way ahead and the results are quite spectacular. A much more interesting format.

Unfortunately these compressed formats are becoming all too common as the main distribution product and listening media. It is still important to work in higher resolution formats such as we do in order to at least have a great mix to convert to a lower res if need be.

I find compressed formats great for sending mixes and things to clients so they can preview things. In that mode they are amazing and very helpful. Well mixed and mastered wave files still sound better to me.

MP3's first remove a great deal of dynamic contrast.  Sometimes it is not noticeable with loud heavily compressed music, but any kind of music that relies on sharp transient responses among the entire frequency range will suffer.  I have recorded plenty of chamber music that becomes lifeless once converted to MP3.  Of course on most consumer systems and headphones, the differences are less pronounced. 

Have you guys tried this MP3 bit-rate blind ABX? It's an eye-opener.

I was feeling pretty cocky after getting 5 out of 5 correct, even if that wasn't statistically significant. By the time I'd done 10 tests, my percentage was down to 83%, and after 15 tests it was 71%. It depended heavily on the style of music being A/B'd. I could nail the Jazz samples every time, but with distorted guitars and wailing vocals it was a total guess.

 To say it "adds" something is totally opposite. As others have already mentioned Mp3 removes large portions of an audio file to make it smaller. The whole idea behind all of these formats isn't improved sound quality. The goal is to remove as much of the file as possible without any noticed difference. With a goal like that it isn't any wonder than anyone who wants to make things sound better might have a gripe with the format.
  Even if we can't always hear a difference, just knowing that the file has been chopped is enough to make any audiophile worth his weight want to run the other way. FWIW you can upload to Soundcloud in high bitrate wave files. This will take more of your storage space but the files will sound better. On my end it sounds like a rhythm track but one missing a lot of umphh.

 At best Mp3 and any other lossy format are a compromise to the sound in order to make it more portable.


 Scientists have figured out the ranges where we hear the best and removed the rest...but in some material you can tell a difference.

 What was that file you uploaded. Is it a differential between tracks like Bit mentioned. Did it sound like that before you uploaded it?

For those of you who are really interested, the forum below hosts many very good discussions on audio compression and the various formats. I learned a great deal from there when I started digitizing my CD collection.

http://www.hydrogenaudio.org/forums/index.php?act=idx

Regards,
Dan

 
 These compressed file formats were a necessary evil and have made a lot of money for Amazon , Apple and others......billions of dollars. Anyone who has seriously wanted to have a big web exposure as a musician has probably made the compromise.

 Back in the days of tape some liabilities were tape hiss and those annoying cracks and pops from pressed records and the potential for scratches. The CD came along and the audio improved, then as I see it we needed a band aid approach to make things work in the age of computer music. They did the best they could with what they had to work with. The continued improvement of these formats and the more powerful computer will hopefully soon close the gap between what we had then and what we need now. Some may say the gap has already been closed.

  IMO the companies who make the big money online need to take more drastic measures to adopt the better formats. Mp3 seems to have become the de facto term for an online compressed file. Most people refer to their portable audio devices as Mp3 players. I hope we can get away from that. I think there is concern in some circles that an artist making a file for mass online distribution needs to insure cross compatibility by continuing to use Mp3.

 Converting to something else may loose customers who still play Mp3 exclusively on their portables even if it sounds better.

bitflipper
Here's how you can get an idea of what the MP3 encoding is removing. 

Put a single hi-hat hit at the front of your song in the count-in area. This will be used later for alignment. Export the project as a normal wave, then create an MP3 from that wave. Now open a new project and import both the wave file and the MP3. Using the hi-hat hit, visually line the two files up. Match their levels to within a fraction of a db (this will take some trial and error). Now invert the polarity of either of them and bounce the two to a third track. If you've matched levels well, this third track will contain pretty much what the MP3 encoder has removed. 

I should point out, though, that this is purely an intellectual exercise and has no practical value. The whole concept behind perceptual encoding is that what's being removed is stuff you can't hear anyway. So just because you can hear it in isolation doesn't mean it was audible in the original mix.

Dave,
 
I've stated this on the forums many many times.
 
The (partial) fundamental flaw with your outline above is that you forgot to remove the ~72 samples that mp3's add in front of the file (I've proved it over and over, and even Beagle admits they are there). That alone will (also) skew the so called null test.
 
I ask you: would you purposely put ~72 samples in front of one of two .WAV files you suspected were not the same and null test them? No? Then why would you line up a .WAV and .mp3 without removing the dead air mp3's add at the beginning of the file?
 
And oh, by the way.... this is not a purely intellectual exercise.