cats squirrel wrote:so, Rap, by that reasoning, a metal layer would be even better than the bitumen, because it has less of an impedance mismatch, which is what we are talking about, not impedance per se. Doesn't work for me. And if frequency is not important, why is it called 'impedance', surely 'resistance' would suffice?
In the instance of a metal then lead would work better and all the maths say so. It's not used in a car for weight reasons, apart from bitumen being cheaper and easier to bond and probably a million other things. And since when have cars been made from the best material available?
A wave is a wave and the maths for dealing with it is the same weather it is large or small, or do you change the way you add and subtract depending on the size of the numbers involved?
It is called "impedance" because it denotes both Resistance and Reactance and is the correct scientific term.
It behaves and is calculated the same way as "wave impedance" and I hope your not asking someone with your first language as his second language to explain the reasoning behind the choice of impedance over say resistance or even why it wasn't called flowerpot? Impedance is the scientific term for it so I see no problem with sticking to that instead of following one of your rhetorical red herrings.
cats squirrel wrote:I believe it is possible to calculate the damping factor of a two (or more) layer system, comprising substrate and damping layer, if all the parameters are known. But it relies on coupling, which I see as 'moving as one'. Just placing one thing on another doesn't guarantee coupling.
You are the one who started making distinctions about coupling and touching Bryan. I just pointed out that those are often the same thing and the distinction you made is not a scientific term so not much use in a formula.
cats squirrel wrote:I think you mean density, mass would just be proportional to the size! given a material.
No I think I mean mass.
A pound of feathers weighs the same as a pound of lead and the same force is needed to move them both. But ad to the mass and more force is needed to move it. Be that vibration or a push.
cats squirrel wrote:But how do you know I overloaded the mass of the system?(whatever that means). Both counterweights were 100g, no cartridge (why is a cartridge needed?) All three readings were taken with the same set up at the same frequency, at the same amplitude signal from the sig gen.
I know because your measurement data is erratic and doesn't correlate to the underlying physics of Acoustical impedance. If you put more energy into the system than it can dampen it starts to oscillate.
The system behaves in the same way as if it is underdamped for it's mass.
As someone on wiki puts it so elegantly:" Underdamped (0 < ζ < 1): The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero."
So change in resonance frequency with it's harmonic dips and peaks will affect the readings depending on time of when the reading is taken apart from any thing else.
Now I suggest you revise and refute the principals behind this in stead of reverting to rhetorical word twisting about cars and cork and what not. Bring some science to the table instead of hunches and do look up the words impedance, dampening, under-dampening and Resistance and Reactance they are not long words and I really shouldn't have to explain to a native English speaker why they are used in the context that they are, I humbly suggest you take it up with your Queen rather than me.