It's been known for many years that in short-term A/B comparisons of otherwise nearly identical audio, people will prefer the version which is a little louder and as a result seems to have a fraction more bass and treble. This is because of a psycho-acoustic effect known as the
Fletcher–Munson or "Smile" Curve, and may be an evolutionary process to make us prioritise sounds which louder and therefore nearer - and might be a predator.
What does this have to do with mp3s ? In a nutshell - encoding an mp3 from a modern CD release which constantly "maxes out" the level results in an mp3 which is more distorted than the original.
This is a result of "
intersample peaks" in the decoded digital signal adding extra clipping distortion in the mp3 encoder - and possibly even more being added by the player itself. Couple this with the swirling, squelchy high-frequency artefacts caused by the data-reduction process of mp3 encoding, and you have the "mp3 sizzle" Professor Berger is talking about.
So the students may well choose this slightly toppier, fizzier-sounding encoded version in a short-term A/B test, especially since modern mp3 encodes have fewer obvious artefacts than a few years ago.
But we shouldn't underestimate the acuity of the human ear and brain. A typical mp3 encode discards 90% of the original signal - and it's harder to listen to as a result. Even without intersample encoding distortion and obvious artefacts, mp3s don't sound as good as the originals in other, more subtle ways. There is a loss of "3D" stereo imaging, a blurring and flattening of the audio. Often mp3s sound as if they have less reverb than the original. Complex sounds lose their interest, the audio overall is less rich and involving - the result is harsher and more crude.
Especially with today's over-compressed, heavily processed music.
As a result, the brain has to work harder to "decode" the music. Listening to music in "real life" is an almost effortless process - listening to a CD requires a little more concentration. Right at the other end of the scale, listening to music squawking from the tiny speaker of a mobile phone, it's often a struggle to even pick out the tune. mp3s lie somewhere in the middle of this - thankfully, closer to CD than mobile !
Here's an experiment you can try yourself, though. Spend a day listening to your favourite radio station. Next day listen to the same station, but streamed on the internet. (The data-compression here will typically sound like an extreme version of mp3.)
How do you feel ?
Personally, listening to heavily data-compressed internet streams makes me feel nauseous. Literally - I don't mean that in some namby-pamby audiophile sense - an hour or two of internet radio and I start to feel slightly car-sick.
The same applies to mp3s, to a lesser extent.
Now obviously not all mp3s are that bad. And some data-compressed audio sounds pretty good - the Ogg Vorbis streams from
Spotify, for example, or Apple's AAC codec . (Ironic that everyone blames the iPod for mp3's ills, even though the iPod's own compression codec sounds substantially better than straight mp3)
But just as mp3 lies somewhere between CD hi-fi and a mobile phone, it also lies somewhere between 24/96 PCM and 64 kbps internet radio - however in this case, closer to the bad end of the scale.
To summarise:
In a short-term test, the distortion/artefact "sizzle" may be appealing to some people, but give them the chance to use a lossless codec like FLAC for long-term listening, and I'm confident they will settle for the better quality.
The great news is that even of I'm wrong, mp3 is already on the way out - it won't be long now before player drive space and internet bandwidth make the requirement for data-compression a thing of the past, and we can all get back to appreciating good audio again.
I mean - does anyone remember how "great" AM radio sounded ?!?
In the last week there has been a lot of attention paid to an informal study made by Jonathan Berger of Stanford University, which he claims shows that some young people (a) prefer the sound of mp3s and (b) that this is becoming more true as time passes.
