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RE: Most likely

Posted by Ron AKA (A) on September 20, 2011 at 15:50:42

In Reply to: RE: Most likely posted by rick_m on September 20, 2011 at 10:17:20:

"But to cut to the chase a bass guitar, large drum, etc will produce sine waves and harmonics of the fundamental. "

Ah... There is the rub, that's totally wrong. Most of the energy and information from these instruments is in the transients, the LF resonances just add some continuity. Listen to a bass run from an electric bass, now play the same run on your synthesizer using just a single fundamental and you will see what I mean. Even there you are producing transients but their net energy is much lower than the tone.

Transients rule in nature and we are very attuned to them, continuous audible sine waves on the other hand don't exist at all in either nature or the manmade environment. If you think that they do, just expand your time horizon, they are but a convenient simplification."
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I'm afraid I have to strongly disagree. Of course there is nothing stopping you from playing electronic garbage noise (square waves, triangles, etc) through an amplifier. I would not call that music. But, if you play a real guitar for example, the tension in the string, the weight of the string, and the length determine the frequency the string makes. That is how you tune it of course. Once those are set, all you can really do is change the amplitude, by stretching it further from the rest position. More amplitude does not change the frequency. The velocity of the string still has to start at zero, accelerate, then slow down to a stop, and then accelerate back. If you plot the distance from a fixed point it executes a sine wave on the time base.

And if you call that first movement of the string a transient, it does not go any faster than the laws of physics allow. It is just like a pendulum on a clock. No matter where you start the pendulum it follows the same path, and at the same frequency. That is why the clock keeps time.

The only thing that changes is the amplitude, but not the shape, or frequency. That is why it is so easy to calculate the required slew rate of an amp. It only depends on frequency and amplitude. We can't hear past 20 kHz, so that fixes max frequency. All that is left is amplitude or in electrical terms voltage. Voltage is low in a CD so slew rate required is very modest.

The thing to keep in mind is the pendulum on a clock. Once you let the pendulum go, there isn't a darn thing you can do to make it go any faster or slower. It will go exactly as the spring mass laws of physics say it will -- in a a perfect sine wave pattern. A guitar string is the same, the skin on a drum is the same. Wind instruments behave the same using air compression as the spring, and tube length with air as the mass. Damping really does not change anything either. The frequency remains the same. The amplitude just reduces faster as damping goes up.


Ron

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