Sound deadening - any material geeks/chemists here?

[Eusebius]

I want to apply sound deadening material to a pair of 3mm thick aluminium speaker cabinets. A good example of this kind of sound deadening is Piega in Switzerland. It appears they use Dinaphon M 6001, in 5mm thickness, made in Switzerland, so I'm looking for an alternative in the UK.

You can see how it is applied in this video. In it they say they started with a bitumen based material, Idikell M 4021, then switched to Dinaphon M 6001, a "heavy synthetic sound deadening film with polymer base, non-bitumen and self adhesive". Also described as "Heavy duty viscoelastic felt" with acrylic adhesive.

from 3.20m

So what's the closest I can come to Dinaphon in the UK, in self-adhesive sheets? Is it

- butyl based sheets

- mass-loaded vinyl sheets

- sorbothane sheets

- somethiing else....?

The requirements are heavy, viscoelastic, polymer, 5mm, self-adhesive.

So....... what's your best guess for a UK product?

[Andy Burns]

I used mass-loaded (barium?) for a noise reducing wall, about 8mm thick, but it wasn't self-adhesive

For Binky, they used "Dynamat"

[John Walliker]

Fundamentally you are looking for three things, regardless of how you actually get them. Stiffness reduces the deflection of the panel for any particular applied pressure. You can get extra stiffness by adding internal ribs, preferably positioned so that they are not exactly half way along the panel. You don't want to divide the panel up into two equal resonators. Mass reduces the movement of the panel for higher frequencies because it has to be accelerated to make the panel move. Damping converts some of the movement that does happen into heat, thus reducing resonance. As you are using box sections, you could fill each of them with dry sand to provide extra mass and damping. For the panels you could have an inner skin and fill the void between the inner and outer skins with dry sand. If you can find something denser such as a granular barium compound or lead shot even better. The advantage of granular materials is that there are lots of places where friction can occur.

John

[Eusebius]

Thanks John. Double layers with sand etc are not on the agenda - more advantageous with larger enclosures. Here the size is 150x150 box section aluminium. So it's a monocoque extrusion, compact and stiff already, not large enough to need extensive bracing. It could be braced but that could be considered overkill. What's needed is damping to stop the aluminium ringing. I'm taking Piega as an example because their cross section is not far from 150x150 in their thinner columns. Their walls are thicker, but I only have 3mm available in 150x150mm.

So following Piega's example which is the closest I have, I'm looking for the right kind of 5mm heavy polymer damping. I just want to know which UK product comes closest to that. Is it butyl, Sorbothane, mass-loaded vinyl or what?

[Eusebius]

Making progress. I've been recommended these 2 products. Dedsheet is Mass Loaded Vinyl. 5kg/m2 and 2mm thick. Quite cheap. The Wilhams is also 5kg.m2 so may be the same. They were closed for the weekend.

"A good thick and ideally self-adhesive mineral-loaded visco-elestic sheet of the heaviest mass per unit area is what you're after. I think the highest grade is 5mm and 10kg/m^2. There's no real harm in using 2 layers if you can only get the thin stuff."

[Animal]

These kind of products seem somewhat popular but I find them hard to justify. If you must use a thin light layer that's 100% waterproof, bitumen gloop is far cheaper. If that doesn't matter, even something as simple as cardboard glued on can stop sheet metal ringing. You could also use flooring vinyl, again far cheaper & widely available free.

[Brian Gaff]

That sounds like what is inside my aging Tannoy speakers. Its a bit like thick rockwool glued to some kind of furry substrate which is glued to the sides of the inside of the cabinets to stop resonances.

Brian

[Clive Arthur]

So much easier simply to evacuate the enclosure.