audio set-up for beginners [continued]

[jhnkvn]

I'd be interested .

Noise dampening insulation basically comes down to two things: absorbing or blocking the sound, and reducing/eliminating the movement of parts which leads to vibration and rattling noises.

To tackle the latter..

You need to understand the three parts of sound deadeners..

1. mass to be dampened (sheet metal in a car)
2. constraining layer (butyl rubber)
3. reflection dampening layer (aluminum layer)

When the mass to be dampened (henceforth sheet metal) is vibrating, it will ring until the energy is either lost in heat, or radiated into the surrounding air as kinetic energy. Vibrations from the cars driving along the road, the air moving past the panels, from the engine just being turned on - all these can excite the atoms in the sheet metal and make it reverberate and we consider this movement as "noise". To negate it, we need to counter the ring with an equal but opposite force as best we can. Thus enters the sound deadening where the constraining layer (butyl) is set to bond with the reflecting dampening mass (aluminum) to the sheetmetal that will respond to a vibration with an opposite vibration -- canceling out the first vibration.

To do this, they use the first vibration impact to push the aluminum layer at a delay that coincides with its distance from the sheet metal. this first impact causes the aluminum to vibrate out of phase with the sheet metal, hopefully causing both of their vibrations to stop dead in their tracks - or close to it. This is why the butyl viscosity and its thickness are very important to get the aluminum layer to vibrate at the right phase-time to the sheet metal.

In reality tho, the vast majority of the dampening is less on the aluminum layer but more on the forces the butyl creates. This is why I don't mind generic OEM butyls with no aluminum layers on it.

But that's the vibration aspect and more geared towards car audio...

If we look at the former..

A piece of paper won't block off sound well. But a huge slab of concrete will. You basically need mass to absorb sounds.

Now, don't worry, there's actually a car running in the Philippines that has concrete poured inside it as a cost-effective way to reduce vibrations and noise. But that car competes in worldwide decibel competitions as any vibration (or out of phase sounds) reduces your score drastically. For one, it has enough decibels to kill a person inside