Subjectivist audiophiles have long maintained that long-term listening is necessary to assess the quality and character of an audio component. Scientific testing methodologies such as ABX, which require quick and conscious evaluation of a change in the sound, have long struck many of us as insufficient, seeming to miss much that affects our enjoyment of music. A pair of Genelec researchersThomas Lund, an audio professional with a medical background, and Aki Mäkivirta, a research and development manager and a Fellow of the Audio Engineering Societyhave published two articles (footnote 1) on the science of hearing and perception, and their findings appear to support such views. Among their observations:
The “perceptual bandwidth” of humansthe maximum size of the [sound] datastream into our brainsis remarkably small. Experts put it in the range of 4050 bits/s: compare that to the worst kind of MP3, which has a data rate of 10s of kilobytes/s, more than 1000 times larger (footnote 2). (No wonder we’re easily fooled by lossy encoding.) Perceptual bandwidth “should generally be considered a scarce resource,” the authors state.
We are not passive recipients of sensory informationhow could we be with such a low perceptual bandwidth? Sensing is an activity; attention is a tool we deploy to select which information we take in.
Only a fraction of the perceptual information we take in is available to our conscious awareness; much of it goes unnoticed. Yet, it still affects us. Weor anyway our brainseven solve problemsunconsciouslyusing unconscious information.
Together, these ideas imply a perceptual landscape far different from the one that people long assumed: Through long experience, we build an internal model of reality and then reach out to test it against scarce, select sensory input. Our ability to function well and make accurate judgments depends on the accuracy of our internal model and the precision with which we correct it with scarce, carefully selected external stimuli (footnote 3).
Models of reality are contextual: An outfielder’s long experience allows him to get a fast start in the right direction when a ball leaves the bat. Our own long experience allows us to detect small changes in what we hear that others cannot (footnote 4). A major theme of the articles is that listening takes time. Indeed, the titles of both feature the phrase “Slow Listening”surely an allusion to the slow food movement that started in the late 1990s (footnote 5). Time matters in subjective listening tests, the authors conclude, in various ways:
Music and language training over years affect our ability to detect short, transient sounds.
Becoming familiar with a reference audio system takes time. “Based on a limited perceptual bandwidth and 8 hours of dedicated listening per day, getting to know a room and equipment in any detail would take at least a week, but assuming years would be safer,” the authors write. “Subjective tests, even producing repeatable results, may have little relevance if confined in time”a challenge for audio reviewers for sure.
Much that matters in perception goes on below the surface, without our explicit awareness. How do we know when our unconscious rumination has matured to the point that it’s time to render judgment? We can’t, so we need to factor in extra time.
What, then, are we to make of ABX tests in which test subjects compare a version of a few seconds of music, jangling keys, or whatever against a reference? Such tests are good for many thingssee this month’s Industry Updatebut far from the last word on sonic and musical significance. When we rely on them too heavily, we miss things.
Here’s one more idea from the article that many audiophiles can relate to. The authors cite an article published in Nature Neuroscience in 2014 that establishes that noise well below the threshold for physical damage can cause auditory stress and impact our hearing. Nontraumatic sounds, including those with “excessive high frequency energy, lack of ‘quiet transients'” (which are removed in lossy encoding schemes) and “interaural strangeness or unnaturalness,” can cause undesirable changes in the “auditory brain,” even if they do not damage hair cells. Aural stress, listening fatigue, and the resulting impairment in our ability to discriminate small differences is familiar to audio reviewers. Scientists have now corroborated our subjective experience.
Which raises another possible objective of audio systems. Accuracyfidelityis, for most serious listeners, the benchmark we measure our systems against, whether we measure fidelity by objective or subjective criteria. But other valid criteria exist. Maybe some listeners just want sound that minimizes, or even alleviates, stress, whether through second-harmonic distortion, suppressed response in the presence region (aka BBC dip), natural interaural relationships, or whatever. Maybe some people just want their sound system to sound good.
Speaking of sounding good: This month’s issue contains the first installment of a new Stereophile column. In Revinylization, Art Dudley reviews the most important of the latest reissues on vinyl. You’ll find the new column on p.125 and here.
Footnote 1: The company’s managing director, Siamäk Naghian, is a coauthor of one of the articles. See here and here.
Footnote 2: I find this number implausibly small, but it’s what is claimed.
Footnote 3: John Atkinson discussed this subject in his 2011 Richard C. Heyser Memorial Lecture to the Audio Engineering Society.
Footnote 4: It’s not only reviewers of course; anyone with good hearing and the right mindset can acquire such skill.
Footnote 5: Later, there was also a brief “slow listening” movement, a response to MP3 and earbuds.
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