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RE: Thanks for keeping me honest

Posted by Charles Hansen (M) on November 21, 2017 at 19:36:09

In Reply to: Thanks for keeping me honest posted by Jaundiced Ear on November 21, 2017 at 17:48:39:

> > Even if there was a distinction, I still don't understand how placing a wooden block in proximity to an electrical signal can change the electrical signal. To my knowledge, wood is not an electrical conductor. How does the piece of wood intrude upon the electrical signal and modify the signal? < <

I have absolutely no idea. All I can say is that it is plausible - here's why. We typically think of a wire as "plumbing". The copper acts like a "pipe" to carry the "electrons". In this model, anything outside of the "pipe" has no effect on the flow of water.

But this is *not* how electricity is carried in wires. Instead, applying a voltage to a copper wire sets up an electrical field in this wire. The free electrons in the copper move in response to the presence of this field. Yet they are not the same.

In the first place the electrons travel at what is called the "drift velocity". This is incredibly slower than the speed of light. In a 2mm wire carrying 1 amp, this works out to 23 microns per second.

And that ignores the fact that the electric field travels more slowly in a wire than it does in a vacuum (where it travels at the speed of light). In most wires the velocity of propagation is between 0.7 and 0.9 times the speed of light in a vacuum. And what factors affect this velocity?

*Not* the conductors, but rather the insulators around the conductors. This implies that there is energy being stored in the insulators, and when looked at on a microscopic level, this is absolutely true. When an insulator is exposed to an electric field there are two main mechanisms for storing charge, both of them rooted in moving that charge in a way that creates a mechanical stress - not unlike pulling the rubber straps on a slingshot stores energy in the straps. (In that case, the molecular bonds are being stressed.)

If the insulator comprises polar molecules, the molecules will attempt to orient in the electric field such that the entire system is in its lowest energy state. If the insulator comprises non-polar molecules, the relative position of the various charged particles (eg, protons and electrons) will shift, again such that the entire system is in its lowest energy state.

Now I don't think it's hard to see how various insulators could affect how the electric field propagates on a wire.

> > Further, if it can reliably and quantifiably do so, why do I only see products like this marketed for audio products? < <

Also a good question, and again one where I think that people tend to think in a rut. Specifically, it is possible for us to build test equipment that is far more powerful than our hearing is - but only with regards to specific parameters.

For example, humans can only hear sounds between 20Hz and 20kHz. Yet it is quite easy to construct microphones that will detect frequencies as low as 0.001Hz and other microphones that will be quite flat to over 100kHz. Or distortion - I don't think there is much evidence that humans can hear distortions at levels much below 0.01% - and even then only under highly specific conditions. On the other hand we can now easily build test equipment that can measure distortion levels 10,000x lower.

Then comes a dangerous (and likely sub-conscious) faith that simply because our test equipment can measure some things more readily than the human ear/brain that it applies to all of them. This is simply not the case.

One trivial counter-example is the ability of the human ear to detect extremely low level sounds - far below that of any test equipment to date. The generally accepted hearing threshold is 0dBSPL. This represents that the eardrum has a peak excursion of less than the diameter of a single hydrogen atom! In contrast, even the best measurement microphone/preamp systems will typically have a noise floor of between 10 and 20dB higher than that.

I believe that (with training) the human ear/brain can be far more sensitive than any test equipment in almost any aspect of sound. The problem arises simply because not all listeners are equally skilled (just as we cannot all play the violin equally well). Then in a (futile) attempt to avoid arguments we turn to "measurement equipment", which turns out to hurt more than it helps. YMMV. Like all of science, it's just a story that has been made up in an attempt to explain what really happens in the real world. Hope this helps.

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