I'm about to buy some lining material to cover the inside of my HVAC silencing boxes. This material is kinda hard to come by here in Italy and I have the chance to buy this product called Stratocell Whisper.
Given the performance at low frequencies and the price difference, I'm unsure on which thickness to purchase, 20mm, 30mm or 40mm.
The price is 15, 23 and €31 per square meter respectively and these are the absorption coefficients:
Is the price difference worth the gain in performance at 125 and 250Hz or is it so poor that it won't matter anyway?
The 20mm and 40mm look reasonably good, considering the thickness and price. The 30mm doesn't seem to have any advantages.
If you can afford it, then I'd go with the 40mm, but do take into account that you will be reducing the internal cross-sectional ares of your silencer boxes, thus increasing the air flow speed. If you designed your boxes for 25mm, then putting 40mm inside them will have a large impact on speed, possibly increasing turbulence and air noise.
So, if the boxes were designed for 25, then go with 20. But if they were designed for 40, and you can afford the extra cost, then go with 40, for sure!
Thanks for taking the time Stuart.
Construction of the silencers was put on hold since I knew the duct liner was going to be hard to find and I was gonna have to work around it, which means I can go for any size I like.
I immediately ruled out the 25mm for obvious reasons and wasn't sure of the advantages of the 30.
Thanks for your opinion. The 40 is considerably more expensive, but the surface to line is not huge so since you seem to agree on the advantages of having that additional low octave covered I think I'm going to go with it.
While I'm here, would you suggest a proper way to glue them to the silencer's wood?
I was told about silicon and other similar methods, but I wouldn' want that smell in my ventilation system. Hot glue was suggested too.
In alternative, these panels can be ordered with a sticky side, but I'm afraid they are not going to be easy to cut and I don't want to waste any product.
While I'm here, would you suggest a proper way to glue them to the silencer's wood?
You can probably just use spray-glue for that. Any good quality construction spray glue should do. But check with the manufacturer, to find out what types of glue they approve, or don't approve.
