Mass-spring system
#1

Mass-spring system

The main idea behind the floating floor is the mass-spring system. The softer the spring, the better the vibration damping. The same goes with the mass – the heavier the better. If the intermediate floor is not heavy, the floating floor does not work because the mass-spring system changes. In practice, an intermediate floor has to be five times heavier than a floating floor.

Impact noise insulation is measured using a standardised tapping machine. A good impact noise insulation L’n,w requires:

Concrete with a floating floor:
Heavy intermediate floor
Soft elastic intermediate layer
Heavy floating floor


The ideal mass-spring system:

[Image: soundinsulation4.jpg]

At the extremes of its displacement, the mass is at rest and has no kinetic energy. At the same time, the spring is maximally compressed, and thus stores all the mechanical energy of the system as potential energy. When the mass is in motion and reaches the equilibrium position of the spring, the mechanical energy of the system has been completely converted into kinetic energy.

All vibrating systems consist of this interplay between an energy-storing component and an energy-carrying component.

The frequency (Hz, the number of vibrations per unit time) of a mass-spring system is

[Image: soundinsulation5.jpg]

Where k is the spring constant (mineral wool) and m is the mass (intermediate floor). The lower the f is, the better the insulation. So by increasing the mass or decreasing the spring constant we can achieve the best insulation.
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