Absolute Polarity—Is Anything Really Absolute (1/5)
Absolute polarity is hi-fi lingo that suggests the sound wave, the recording of the sound wave, and the sound wave generated by your playback system produce the compression phase of the initial wave at the same point within that correlated time reference. This concept has little to do with hearing or not hearing bears, but a little.
Confusing? Yes. If you are hearing about it for the first time. But move beyond hearing bears—or not—laying cable in the woods, and this concept quickly increases in complexity. Keeping it simple [clear’s throat] let’s take a page out of Harry Olson’s book: Music, Physics and Engineering. Imagine a balloon inflated and tied. Inside the balloon the air pressure is higher than ambient, the balloon’s thin skin, imagined to be two dimensional, applying force and keeps the pressure different and contained. Surrounding the balloon is only undisturbed air. Inside the balloon also undisturbed and sound-free. Now image a pressure switch type of microphone that could pass through the air without generating a disturbance and one that could pass through the balloon’s envelope, also without generating a disturbance. What would the mic probe show? If ambient pressure surrounding the balloon was referenced to neutral, zero on the horizontal axis of the cartesian plane, the data from the mic would simply show zero while the mic was passing through ambient air. Once this special mic entered the balloon the pressure would increase and the mic system would then show increased pressure and the data would move up from the zero plane, assuming we set the system up to correspond with increased pressure, and that the data would move up at that level-x for as long as the mic was within the balloon–falling back to zero once the mic moved outside the balloon again.
The balloon’s internal higher pressure represents compression in air, corresponding to a loudspeaker’s “cone” moving out from the loudspeaker, toward the listener—kinda-sorta.
Absolute phase requires the following:
that your in-hand recording of this above outlined imagined balloon event is as it was relative to the pressure of the balloon—the recording showed the balloon had increased pressure over ambient and not a decreased pressure over ambient (negative space…).
That when the recording is played back through your playback system that the positive pressure of the balloon is reproduced to the observer as a positive pressure event.
Correlating this to say, a recording of a cannon blast [1812 - hellya]. We can see that the cannon creates a compression wave for the initial attack, as it is a large increase in temperature and causes such an action in air. Absolute phase as a concept dictates that the recording of the cannon blast shows positive pressure on the initial attack, and that the loudspeaker then cause the same (loudspeaker cones/membrane moving toward the listener). Absolute phase accomplished.
For the second part we will explore realities and consequences of absolute thinking, I mean absolute phase.
Think-abouts, for next time:
Can you have a compression wave without a rarefaction?
What examples of square-wave sound waves can you think of in nature?
How does/might/can absolute phase be relative to bowed instruments, woodwinds, how about plucked/hammered strings?
And how the hell do you know the “absolute phase” of the recording you own of the 1812 Overture anyway.