A topic of enduring interest for me is the audible benefit (or otherwise) of high-resolution audio such as SACD, the near-obsolete DVD Audio, or increasingly downloads offered in 24-bit/96 kHz or better resolution, versus the 16/44 resolution of CD, also known as “redbook” because this part of the CD’s specification was defined in a red book.
I wrote a piece on this last year, which is still among the most-read articles on this web site, so I am not the only one.
Today I came across some old articles by Dave Moulton which I enjoyed. He is an audio engineer who has also worked on the subjective measurement of audio systems – in other words, if you are a maker of audio equipment you can go to him and say, “this new feature of ours, does it really make a difference or sound better?”
Moulton wrote a series of pieces starting here which examine the human aspect of audio technology. One of them explains why we exaggerate small differences. He is also, as I suppose I am, sceptical about the benefits of high resolution audio:
… the resolution benefits of 20-bit and 24-bit signals are not only hard to hear, they’re, well, inaudible as we currently do it. Uh-oh!
and I like his awareness of the “system” – not just the equipment in our living rooms, but the entire chain:
When we have a SYSTEM with really smooth response (say, +/- .5 dB) from 30 Hz. to 17 kHz., from microphone diaphragm to eardrum, well, then we really have something to brag about. And UNTIL we can do this, it doesn’t do a lot of good to invest a lot of bucks in dramatically extending the response of a single stage.
Another series of articles is specifically on high resolution audio.
Of course high-resolution is valuable for mixing, mastering and audio processing, where there is a danger of cumulative error; and I accept that there could be cases where there is some small benefit in high-resolution playback equipment. That said, this is a much-misunderstood area; and audio vendors are happy to exploit our natural instinct to believe that bigger numbers must mean better sound.
I still see people drawing sound curves with steps in them to show that increasing the sample rate must improve the accuracy of the curves – when it has been shown that this is not the way digital audio works. There are some excellent papers here (click the link for Support) by Dan Lavry of Lavry Engineering, makers of high-end digital audio converters, which explain the mathematics:
Let us review Nyquist Sampling Theory: A sampled waveforms contains ALL the information without any distortions, when the sampling rate exceeds twice the highest frequency contained by the sampled waveform. Note that once we agree on what constitutes audio bandwidth, we need not sample much faster than twice that bandwidth to have the ability to retrieve 100% of the original signal.
Despite my high-res scepticism, I am still keen on getting the best sound I can afford at home. In fact, this is why it is important to have this debate. We need to know what it is worth spending money on.
In the end, it makes sense to invest in differences that you can easily hear, such as those between loudspeakers, rather than in differences that are subtle to the point where you can debate whether they are audible at all.