The Absolute Sound

Written by Richard Murison

Let me describe something I was very fortunate to be able to try one time, but which very few of us will get the opportunity to experience.  I am talking of entering a professional anechoic chamber.

An anechoic chamber is a room specially designed for the purpose of conducting carefully calibrated acoustic measurements.  In normal rooms, any sound generated anywhere within the room will travel rapidly to all other parts of the room by bouncing off the walls (including the ceilings and floors).  Therefore, if we attempt to measure the sound in a room we very quickly find that it is impossible to distinguish between sounds which originate directly from the source and those which have travelled via multiple bounces off the room boundaries.  This is important, because these multiple signal paths cause the signal to be reinforced, cancelled out, or anything in between, thereby rendering many forms of measurement entirely useless.

The solution is to create a room in which sound waves, when they hit one of the walls (or floors, or ceilings), are instantly and totally absorbed and none of it is reflected back into the room.  Such a room generates no echoes, and is therefore termed ‘anechoic’.  These are particularly useful for designing things like microphones and loudspeakers, and enable detailed and accurate measurements to be performed in a way that would be virtually impossible otherwise.  You’d think that every loudspeaker manufacturer would have one, but they don’t.  They all wish they did, but most of them can’t afford such a preposterously expensive luxury.  The best they can hope to do is rent time in somebody else’s (most likely in a university, or institutional research center).

What is particularly instructive is to get somebody to step into an anechoic chamber for the first time, and ask them to sing a song or play an acoustic instrument.  You can bet your mortgage that they will stop singing or playing within less than a second.  What they hear are sounds so alien to them – such a departure from their expectations – that they can’t help but stop abruptly.  It only works first time, because once you know what is going to happen you aren’t so taken aback.

The sound of a voice or an instrument in an anechoic chamber is just so unlike anything you have ever heard before that it stops you dead in your tracks.  Same goes for a loudspeaker playing in an anechoic chamber.  It will exhibit an unappealingly dry sound, devoid of all character, expression, depth, or life.  An anechoic chamber is a profoundly unnatural environment.

And yet, the sound of a voice or acoustic instrument in an anechoic chamber is the most accurate representation of that sound.  It is precisely what that voice or instrument actually sounds like.  Only the sounds travelling directly from the source to the listener will reach the listener.  All other sounds will be totally absorbed as soon as they hit any of the walls.  This is as accurate as it gets.

Outside of the anechoic chamber, the sound you hear is the sound of that instrument playing in a given room.  The difference between what you hear inside the chamber and outside is the contribution of the room to the sound.  That contribution is colossal, and is fundamental to how we perceive the sound.  The magnitude of the difference serves to ram home the point that everything we hear every day is the product of the various sound sources modified by the environments in which we both exist.  The same orchestra, for example, playing in two different concert halls often sounds like two different orchestras.

This is important to grasp, because it serves to illustrate the futility of one of the holy grails of the audio industry – or more precisely of many of the critics who presume to influence the industry as to what it should be doing.  This particular sacrament requires that the goal of a high-end audio system is to recreate the sound of the original instrument.  A very noble aim, wouldn’t you think?  But the actual sound of the original instrument is the desiccated sound from the anechoic chamber, and that is not what your typical recording engineers attempt to capture.  All they can ever hope to capture is the sound of the original instrument played in the original location.  [Now that is not entirely fair.  Many recording engineers are aware of these limitations, if not necessarily in those terms, and preferentially employ techniques intended to mitigate the effects.  But that only serves to further complicate the issue.]

This presents us with two separate philosophical problems.  First, how are we to know what the original performance actually did sound like in the original location?  Unless we were there at the time, we can’t.  Second, our loudspeakers are located in their own separate and different acoustic environment.  If ‘simply’ reproducing the musical instruments themselves in our own listening environment is challenging enough, it is a different challenge entirely to reproduce the complete audio environment of one room inside an entirely different room.  For example, consider recording a violin in an anechoic chamber, and then trying to reproduce the sound of that anechoic chamber in your own listening room.  Take it from me, without an anechoic chamber of your own, it is not possible to come even close.

As far as tonality is concerned there cannot be practical absolutes.  While the broad brush strokes of tonal color are provided of course by the instrument itself, the fine details are dominated by the acoustics of the room.  So when it comes to judging sound reproduction there can be no such thing as Harry Pearson’s much vaunted “Absolute Sound”.  There are no absolute points of reference other than an anechoic chamber, and nobody would want to listen to anything that sounded like that.

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