Issue 218   December 2011
The Smaller Difference
Editorial By Robert Harley

 

  I've long been fascinated by the idea that if the sound is different, then signals are different. That is, if you hear a difference between, say, two aftermarket power cords, it follows that the electrical signal driving your loudspeakers must be different, which causes the loudspeaker cones to move slightly differently, creating a change in the patterns of vibrating air molecules. This change is interpreted by our brains as greater or lesser musical realism.

The concept is axiomatic, of course. But in the real world some of the differences in the musical waveforms traveling down loudspeaker cables, or the acoustic compressions and rarefactions striking our ear drums, must not just be vanishingly small, but miniscule beyond our ken. These differences in the shapes of the musical waveforms are far too small to see or measure with even the most sophisticated technology, yet we as listeners not only routinely discriminate such differences, we find meaning in those differences.

This phenomenon is partly explained by the lack of a linear relationship between the objective magnitude of a distortion and the musical perception that distortion engenders. You might replace a cable and suddenly realize that in a familiar recording what you thought had been a guitar toward the back of the soundstage was actually two guitars. The difference in the electrical and acoustical signals produced by the different cables is infinitesimal, but the musical difference — one guitarist or two — is profound.

Concomitantly, you could introduce 2% second-harmonic distortion (a huge, easily measurable objective change) into an audio signal and perhaps not notice it, and if you did, the distortion would not be unpleasant, producing a warmer, plumper sound. Yet reconstruct an analog waveform from digital samples with a clock whose timing precision varies by just a hundred picoseconds (0.0000000001 seconds, or one one-tenth of a billionth of a second, the time it takes light to travel about an inch) and we hear the change in the analog waveform's shape as a reduction in spaciousness, hardening of timbre, a “glassy” character on high-frequency transients, a softening of the bass, and an overall reduction in listener involvement. Some of the distortions produced by an audio recording/reproduction chain don't occur in nature and thus strike a discordant note when processed by our brains. Sounds produced by nature and by musical instruments virtually always have a significant second-harmonic component, but we never encounter in nature a waveform with the specific distortion introduced by digital jitter.

Humans seem to be hardwired to discriminate very small differences between similar things. Think of the widespread connoisseurship in any number of fields: wine, dog and cat shows, types of carnuba car wax, coffee, cheese — the list is endless. Moreover, we don't care about differences between coffee and tea, or between dogs and cats. We're somewhat more interested in the differences between breeds of dogs, but some of us are absolutely obsessed with tiny variations within a specific breed. Meridian Audio founder Bob Stuart summed up this phenomenon with the phrase "the increasing importance of the smaller difference."

Music is different from other forms of communication in that its meaning and expression are embodied in the physical sound itself. The vibrating air molecules striking our ear drums are not a representation of the music, but the music itself. Contrast music listening with reading type on a page (or pixels on a screen), in which the letters are merely symbols that stand in for the underlying meaning. Distort the type, or read in low light, and the meaning remains unchanged. But change the shape of a musical waveform and the composer's or performer's expression is diluted. You might not hear a subtle dynamic inflection, miss a crucial rhythmic interplay, or be oblivious to the way tone colors combine that would otherwise create an ineffable flood of emotion. The sound contains the meaning; it is not a representation of the meaning that can be divorced from the physical phenomenon conveying it.

All these observations point to the fallacy that technical measurement can replace the discrimination ability and auditory-processing power of our ear/brain system. Even if we could see the tiniest distortions in a musical waveform, this analysis would still remove from the process not just our hearing system, but our interpretation of how that distortion affects the communication of musical expression. Because music speaks to our humanity, a piece of test equipment, no matter how sophisticated, can never replace sitting down between a pair of loudspeakers.

 

 

 

 

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