This should have been done by the author of the research paper. It took me about 15 minutes with standard software (Adobe Audition) and completely confirms what common sense and our own ears tell us: the classical music track is radically different in its energy and spectral content to the pop track. Consequently the entire theory proposed is built on unsafe foundations, in my opinion.
Attached is the technical review of the classical (Beethoven) and pop (Kylie) tracks as supplied. I hope I've annotated the images to make sense of them. As you may be able to see, as far as this Beethoven example is concerned, it is clearly mono as the L & R traces (top chart) are identical. As the audition suggested, in this classical example, there is almost no energy above about 7kHz. Contast that with the Kylie which shows high level energy (red streaks) right out to the CD cut-off at 22kHz.
All data compression systems have to walk a fine line between discarding sound to reduce bit-rate and the consequent potential loss of fidelity. These two examples would stress a coding system in very different ways: the classical piece would compress easily as it has limited loudness and limited frequency range: the pop track would be more difficult to compress because there is so much high-level energy at high frequencies ... a nightmare scenario for a compressor because to trace the high frequency waveform accurately needs more data, and that is the very thing that a compression system doesn't want to have to do!
NOTE: This does not imply that all classical music or all Beethoven recordings have these characteristics - we have only looked at one old mono recording, the one the author used.
Alan A. Shaw
Harbeth Audio UK
It appears that the author may have invalidated his own hypothesis (i.e. rendered it incapable of meaningful proof) but offering poorly-chosen samples.
But it does beg an interesting question. How would one choose valid samples to test whether there was a difference in compressibility between pop and classical music? Both recordings should be stereo, obviously, and both should be considered to be "good quality" recordings. Beyond that, however, what would the criteria be? With a small sample size, could not any differences (assuming there were any) be ascribed to the spectral and other differences between individual recordings? Would not one have to use a fairly large number of recordings before drawing any meaningful conclusions, even assuming other variables could be equalized?
A cursory reading would clearly show that Robin Whittle was aware of the Beethoven audio clip was in mono. On further readings, you will find he did comparisons with all tracks in mono. He also mentioned that the original audio files were missing. Whatever it is, if one pauses for a moment and wonders why would one take Whittle statics to form a basis of Dr Hudson's hypothesis, then I wouldn't dismiss it outright.
Whittle's compression data was the basis for another thesis by Tatung University (yes. It is ranked 1450 in the world) and also used by Nanyang University (yes, again not the best in the world). Probably there are more since this is also part of Wikipedia but I have no time to search and knowing this post is very unlikely to pass the mod.
And how could BioMedCenter approve unsound research papers, which were peers reviewed? So we have statistics published in the 90s used by Universities and researchers like Hudson in 2010 but all of them somehow overlooked the mono track which came under scrutiny within half an hour of me posting the link here! Amazing!
For a truly educational forum as one aspires to be then the least we can do is at least honour Hudson's request, i.e. I quote "As with all generalisations, a frank discussion of the presence of both supporting examples and counter-examples will illuminate where and why the musical information compression hypothesis breaks down".
This article is not as much misleading when comparing the Hifi News article on Festival of sounds, which only received a mere 22 response out of the 3000 attended and yet a conclusion was drawn that all couldn't tell the difference between live and recorded.
I think the issue here is not so much the compressability of one type of music versus another but the rather romantic hypothesis associated with the research. To quote the paper ...
etc. etc. etc.. Contrast that with the opening Summary of the BBC report ... (attached). A very different style of writing indeed.The adaptive solution to this problem of scale is information compression, thought to have evolved to better handle, interpret and store sensory data. In modern humans highly sophisticated information compression is clearly manifest in philosophical, mathematical and scientific insights. For example, the Laws of Physics explain apparently complex observations with simple rules. Deep cognitive insights are reported as intrinsically satisfying, implying that at some point in evolution, the practice of successful information compression became linked to the physiological reward system. I hypothesise that the establishment of this “compression and pleasure” connection paved the way for musical appreciation, which subsequently became free (perhaps even inevitable) to emerge once audio compression had become intrinsically pleasurable in its own right.
It reminds me of the beauty and simplicity of the BBC R&D papers from thirty years ago - attached one covering the spectral content of pop v. classical music. No romantic talk there. Just hard facts. Had I not fallen under the spell of the sublimely deceptive simplicity of these BBC papers when I was a young man, we, Harbeth, wouldn't be here today. And you wouldn't be enjoying the fruits of that BBC legacy.
All that's required to really get to the heart of any published paper (assuming it's not smothered in obscure mathematics) is to read it from the conclusion backwards - and apply a really big dollop of good old fashioned common sense asking yourself "does that agree with my own personal experience?" If it doesn't, and you trust your ears, then you need to hunt for clues as to why the reporter - or you - are wrong.
Alan A. Shaw
Harbeth Audio UK