[Drumhum]

The Blue 1,

Good point. The "sound" of the Mp3 will come from the encoding rather than the decoding - unless there is some "tweaking" going on in the playback (like eq boosts etc)

And this has been demonstrated by OP MurrayHill.

I can't go along with the idea that an MP3 file is essentially the same as a Wav file though, and that you can playback an mp3 in a wav player so long as you can "fool it" into thinking its a wav. the data structure is completely different.

for example...

In Mp3 as well as the clever psycho-acoustic/perceptual encoding stuff going on there is also some data compression (called Huffman) that is lossless. Its like the way we zip files. This part needs to be "unzipped" for the data to make sense. No wav player will do this.

Another example is how stereo files are handled (this is where "stereo", "Joint Stereo", "dual mono" options in better encoders come in). One technique to reduce data is to not duplicate identical sounds from each stereo channel - in other words the Mp3 encoder does not encode each channel separately but takes it as a whole. if the same sound exists in both channels (eg a sound panned centre) it will just encode one of them and throw away the other. the decoder re-constructs things on playback.

Note also how you need "special" software to edit mp3's: the format wont allow just a cut in the middle of a file like PCM files (like wav) do. Software that allows editing is really doing a fair amount of work - it essentially notes where you want your cut and then generates two new mp3 files from the original. when you edit a wav, you really are just moving chunks of binary around.

And then there's MP3's encoded with Variable Bit Rate which would be wholly incompatible with the CBR nature of WAV and AIFF.

There is so much more to this - I'm working off pretty vague memories from when I looked into it so don't quote me to the letter! There's loads of articles and papers to google if one's drive for geek-dom is strong enough!
It is darn clever stuff though.

Note though that just changing the dot-suffix to wav wont necessarily make software play a file like a wav. In the mp3 there is extra data that has all sorts of info to tell the player what to do - indeed another reason why I can't see how a wav player wouldn't have a chance playing back an mp3. If you found it worked for you I'm sure its because the software just 'realised' it was really an mp3 - try changing a *.doc word file to .wav and see if it plays in your software.