Hearing vs. Measurement by Richard C. Heyser (Mar. 1978)

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Surely the end product of audio technology is the listening experience.

We must never lose sight of this fact.




No matter how exotic our instrumentation, no matter how impressive our mathematics, it is what we hear, not what we measure or compute, that is the final arbiter of audio quality.

But this does not mean that we should turn away from technology when attempting to assess or improve audio equipment. It means that we should become more aware of the proper role that is played by instruments and mathematics. For it is still the sole dominion of technology to give us objective and repeatable measures of our gradual climb toward perfecting audio systems. And until that day when we can quantify human experience and emotion, it is still our standard of improvement.

Yet we face a dilemma in modern audio technology: Our measurements do not always correlate with what we "hear." Are the measurements wrong? Is there something in human perception which transcends our technology?

Are there "hidden variables" that we overlook? Or are we fooling ourselves by creating a mystique of the golden ear? Whatever your personal views on this matter, there is one thought I would like you to ponder. ..the effect that modern sound reproduction strives to achieve is the creation of an acceptable illusion in the mind of the listener.

Illusions It takes no small amount of intestinal fortitude to stand up and tell an industry striving for technological perfection that what we are really trying to do is create an illusion. Yet that is the inescapable conclusion to be drawn from analysis of our present situation.

Almost without exception, the physical sound field in a listening environment could not in any way be created by actual sound sources located where we perceive them to be.

There can be no stage-center vocalist located between our stereo loudspeakers and 10 feet behind a back wall. There can be no string section stage-left and 30 feet back. Yet that may be the illusion we perceive from a good stereo reproduction. We fuse these illusions from two discrete sound sources plus internal reflections in our listening environment.

The physical sound field which a modern sound reproduction system creates is definitely not congruent with the apparent sound field which we hope the listener perceives. What a listener "hears" is not a reconstructed hologram of a live performance. Instead he is subjected to a carefully contrived sound field which is intended to stimulate a specific type of perception.

The listener is not a dupe in this circumstance, but is a willing participant who will often knowingly reject interfering sensory cues that would otherwise damage the illusion.

The enhancement of this illusion, as a commercial enterprise, involves art as well as science ... psychology as well as physiology.

Ingredients of Listening

Consider the ingredients of this listening experience. Let me define perception as the awareness of the world about us which we gain principally through sensory experience.

While the sensory stimulus may be the result of independent processes, the perceptual image which we fuse from these senses is combined within the higher levels of the mind into an interrelated structure. Sensory imagery involves a multi-dimensional structuring in which ordinary physical space comprises only part of the dimensional frame of reference against which we form perception. This perceptual structuring is based on physical and emotional experience and is such as to align the majority of sensory experience at any moment with a consistent world -picture in our minds. The perception of sound involves more than just what we "hear." It is a holistic experience that involves not only the other senses, but past experience and present emotional state as well.

Not all of the sensory stimuli or prior experience need necessarily agree in order for us to form a perceptual image. Consider the art of a ventriloquist.

Through manipulation of acoustic, visual, and associative relationships, a ventriloquist can project an illusion quite inconsistent with reality. I suspect that a ventriloquist would find it difficult to confuse a blind person.

This deception, which we find so entertaining, indicates a deep structural compatibility within human perception. Not only can we cope in a world which presents us with a continuing barrage of sensory stimuli, some of which can be misleading, but we can willingly "shut out" certain cues in order to enhance our perception.

These are things that I, as a reviewer, must recognize whenever I form a value judgment on the listening qualities of a product.

On a survival level, the structuring of perceptual cues should relate to physical reality. A cave man would have been easy prey for a tiger which was seen on the left, heard on the right, but could bite him from the rear. We align our perceptual cues into a meta framework which I have referred to as a "rightness of perception." But on a more leisurely level, otherwise significant structural cues can be slotted into a lower hierarchical level of importance to perception. The world-image which we fuse in our perception may seem quiet real to us, but it does not necessarily coincide with ingredients of a physical reality.

Not a Hologram

The often overlooked art of recording lies in knowing how to structure the acoustic cues so as to enhance either the illusion of reality or the evoked emotional experience. Simply sticking microphones in a place where recordings are to be made will not do it if we want the proper listening experience from our present reproduction technology.

I must point out that it is theoretically possible to record a dynamic diffraction pattern of an acoustic performance-a hologram.

Some day we will do that, but it is not what we now record. We do not record a hologram; we do not even pretend to record a hologram. Nor do we even pretend to play back a reconstructed holographic sound field. Yet, I submit, much of the hoopla of present audio component measurement technology is based on the assumption that we listen to a reconstructed hologram.

The component designer who, in good faith believes he is thoroughly measuring the performance of his product, tacitly assumes that perfection is a reconstructed hologram. He then compounds this problem by using distortion measurements which are based on linear mathematics (I will have more to say on this important matter at another time). When a nontechnical listener hears this product as part of a modern sound reproduction system, he may perceive an unpleasant warping of the illusion. It is distorted as a perceived experience. The designer is enraged that his product--which measures double 0 nothing percent "distortion" can be perceived right through the much higher measured distortion of other components. Obviously, in the technologist's eye, the non -technical listener is a freak to be ignored. Particularly, since this listener uses weird words such as furry to complain about the imperfections he perceives. The result is an industry split right down the middle, with math and fancy test instruments on one side and dissatisfaction expressed in flowery rhetoric on the other side.

Both sides of this controversy have been squared off against each other for at least 50 years, and neither will give an inch to the other.

It is my opinion that before we can try to answer the question "why can't we measure what we hear?" If we do not know what we are trying to do, then how can we expect to know how to do it better?

We align our perceptual cues into a metal framework which have referred to as a "rightness of perception."

I submit that what we are trying to do in today's technology is provide a particular type of listening experience under the limitations imposed by our ability to recreate a physical sound field. A great many years from now we will be able to record and reproduce an acoustic hologram, assuming that this is what the listener wants.

Meta-Language

Once we recognize that the actual sound field in a listening environment is not identical to the sound field which we may perceive, we get a whole new perspective on the problem of being able to measure what we hear. It is the illusion of reality, not the reality itself, that we must measure.

Now, I know that such a statement may turn a lot of people off, but do not be misled by any emotional reaction to my observation that the listening experience involves the structuring of an acceptable illusion by means of artfully contrived sensory cues. This does not mean, as I pointed out earlier, that we must abandon technology. It does not mean that at all. As a matter of fact it directs us back toward technology of a much higher level.

Consider this: Our entire multibillion dollar sound reproduction industry depends, in one way or another, on the observation that most persons will experience the same type of illusion if subjected to the same type of stimulus. Stereo would have been a total flop if the illusion of lateralization and depth were a random occurrence among the listeners. In other words, there is a commonality of structuring which shows the promise of being analyzed by a higher level of technology than that which we now use.

This higher level of technology might serve as a meta -language which we can use to translate between certain objective and subjective descriptions of the same event. And isn't that really what we want to do if we are to correlate what we measure with what we hear? Language of Perception

Let me pursue that particular point a little farther. If human perception is structured in the manner I indicated earlier, then any attempt to convey information about personal impressions of a perceived experience might use terminology dependent upon that structure. The language of perception may depend upon inter-sensory analogies of form. We might describe our impressions of a sound in terms of shared experiences of sight, touch, taste, or smell, as well as sound.

A language capable of conveying information about our perception may be syntactically structured to evoke the appropriate sensory imagery. Seen in this light, the symbolic, often flowery, terminology of subjective audio begins to make a bit more sense (no pun intended). There is a language here, and words such as sharp, bright, and furry do convey meaning at an experiential level.

But if this language of perception is based on structural rules derived from, or consistent with, physical experience, then there is a conceptual link with objective measures of the ingredients of that physical experience.

But, let me come at this from another direction. If, as Einstein cautioned, it is the theory which decides what we can observe, then the frame of reference establishes the form which that theory will take. When two observations are related to the same event but use different frames of reference (such as our perception of a measurable sound field) then there is a conceptual link between these frames of reference if the observations are internally self consistent.

If we "hear" the same sort of thing every time we listen to the same set of physical stimuli, then, somehow, the measurements are related to what we hear. But that relationship is never a congruence when the frames of reference are not congruent. It is a foolish person who will draw conclusions about the "audibility" of certain technical flaws in the physical reproduction based on limited "listening" tests and ignorance of the possible differences in the frames of reference.

The first step we must take in quantifying perception is to learn the cipher of its language. But we must do more than just compile a dictionary of terms, because such a list of terms will remain a book of "seven seals" unless we try to understand the structure to which this language is applied-the frame of reference.

Altered Awareness

There is a final point I would like to address in this brief discussion. The illusion which we strive to achieve in the mind of the listener does not have to be an illusion of physical reality. The illusion can be that of an emotional experience based on a frame of reference in which the ingredients of physical reality are of minor importance.

No two persons need necessarily have identical frames of reference for perception. Indeed, our individual frame of reference can evolve and change from one time to another and from one situation to the next.

This altered awareness may be the result of a deliberate act on the part of the observer, or it may evolve quite subconsciously as a result of experience, training, or even emotional state.

I present this conclusion with no intent of becoming embroiled in philosophical discussions of: "What is reality?" or "How do I know that you hear a C major chord as I hear a C major chord?" Instead, I am sticking my neck out and presenting certain technical interpretations drawn from a transformational geometry based on the concept of frame of reference.

This structure of perception or conscious awareness, or whatever you choose to call it, is all too frequently overlooked when we consider the superficial technical aspects of audio.

But these things are there when we really strive to understand what it is that we are attempting to do in audio-when we realize that the end product is the listening experience.

(Source: Audio magazine, Mar. 1978, )

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Updated: Wednesday, 2017-03-01 23:01 PST