A quick run-down, in the order I read them in the paper:
1. Analog or digital, there are analog elements that introduce nonlinearities, and these cause THD and IMD. I agree IMD is more objectionable to listeners because it generates non-harmonic tones that are more easily picked out. I see what they are trying to do in distinguishing analog from digital nonlinearities, but in truth thee are present in all systems. Digital converters also introduce their own "analog" nonlinearity through e.g. nonlinearities in the reference ladder or delta-sigma modulator's cells.
2. "Digital distortion" is a pretty ambiguous term; fortunately, they go on to define a few causes.
3. Jitter is actually explained well, imo. I do not equate it to phase modulation, nor does the standard, but I don't think there's anything wrong with that. They did it to relate it to other terms audiophiles might recognize. I can quibble about how accurate an analogy that is, but it's an analogy, no worries. Overall, the jitter write-up is pretty durn good.
4. The discussion on quantization noise is a little misleading though not inaccurate. Among things not said are that, as the signal fades away, you can't hear it anyway, whether it is above or below the quantization noise. And, we can actually pull signal out that is below the noise floor, a marvelous ability our ear/brain system has. And most DSP systems, for that matter (we and it can average out the noise to extract signal information below the noise peaks). And, those steps are pretty darn small, even for a 16-bit converter. Remember, the SNR is ~98 dB ideally, and most rooms have nowhere near that much dynamic range (typically maybe 40 - 50 dB up to perhaps 120 dB at "the chair", so realistic usable dynamic range is closer to 70 - 80 dB).
5. Dither does not "remove" distortion; it will decorrelate quantization noise and provide a noise floor that may sound a little less "harsh". This may be a bit of a semantic issue (similar to the discussion Amir and I had earlier): distortion to me is not the same as noise, and in my little world of ADC and DAC designers quantization noise and distortion are two different things, generated by different sources, with different spectral content, and different impact/implications on the system (audio, radio, radar, lidar, whatever). One of the largest benefits of dither is to suppress tones in delta sigma modulators. Those tones are not harmonically related to the signal, can be fairly large, and thus quite objectionable.
BTW, few converters (ADCs or DACs) over 16-bit resolution improve much in the way of noise floor or nonlinearity (distortion) in the real world, although the theory is there and some have certainly done so, though I am pretty sure the only true 24-bit ADCs I have seen have bandwidth far lower than audio. Also, dither
reduces the SNR (it adds more noise, after all), but is generally worth the trade.
6. Delta-sigma modulators were around in the 30's, I think; Sony is being given a bit too much credit. What needed to happen, and has, is to develop better filters and practical digital processing to make them work in the real world. Sony was a major force on bringing them to market.
Doubling the sampling rate of a conventional converter adds 3 dB, not 6 dB in SNR. There are enough other "good" numbers that I suspect a typo.
I don't think noise shaping can improve the noise floor of a recording though noise shaping with filtering (interpolation) of the 16-bit source can help. "Perceived" may be the key word in that paragraph...
In my experience, 24-bit systems are used to provide increased dynamic range and headroom when multiple sources are recorded and combined through the mastering process. A good 16-bit recording and a good 24-bit recording are virtually indistinguishable in my experience once the mastering is done, but what happens along the way is easier with more bits to play with.
7. I was getting tired so just skimmed through the aliasing section. It appears correct and makes good points about the filtering problem Nyquist-rate converters all have (audio or microwave).
So, when all is said and done, after a bit harder look, there is actually little to quibble about and the overall article seems reasonable to me. I thiink a couple of things just stood out when I first read it. And, please do not take me for a pompous a** -- I was asked to express an opinion and did so. I am reasonably expert in my field, and admire the work and appreciate the effort (that article undoubtedly took hours and hours of work!) Benchmark put into that article. Two thumbs up with maybe a smudge here and there a little white-out might fix.
References -- many, many years of swearing at converters of various flavors, a decade or so of live and studio audio work and installing and repairing systems a couple of decades ago, the IEEE Standard cited earlier, a plethora of IEEE and AES articles, and perhaps:
Candy and Temes,
Oversampling Delta-Sigma Data Converters, IEEE Press, 1991.
- an update of the delta-sigma book I did not bring home, sorry
Kinsler et. al.,
Fundamentals of Acoustics, 3rd ed., Wiley and Sons, 1982.
Everest,
The Master handbook of Acoustics, 2nd ed, TAB, 1989.
Oppenheim and Schafer,
Discrete-Time Signal Processing, Prentice-Hall, 1996 (I think; I only have the earlier version at home).
I could cite many, many more but am tired and lazy; please let me know if you want a specific topic reference.
HTH - Don (I was gonna' list credentials, but you have no way of verifying that I didn't just make them up, and virtually all my work has been behind the scenes and unpublished anyway, like that of many engineers; the fun's in the lab <and in the air, and even in space, in my case>, not the papers!)