neverest® ESD 4 inch in-line Duct Sound Absorbing Tool Sound Insulation Silencer for Round Metal Ventilation Pipes

I lined 2-3 of these in a row in some of my ducts with a little over half of the insets punched out as holes and the remaining protruding halfway out to form a kind of rotated interlocking sound maze of baffles. Lets air throught and seems to work very well to trap and cut sound down 80-90%. Went from it sounding like people were talking directly into the vents to pretty much nothingDefinitely does squat if you buy only one and take all the insets out and expect it to magically block sounds. That's not how sound waves work.

I used these to reduce noise transfer in the heating vents between my upstairs and basement. It is amazing how well they work.It took me a couple tries to get the right size. They do squish a little bit once you take out the internal pieces to make the holes for airflow, so you can go a little bigger than your opening - like 1” but not 2”.Had been planning to install multiple in a row as suggested if needed, but i installed one at each upstairs opening and one at each downstairs opening, and there was no need for more, as I can listen to my music almost as loud as i want and barely hear it below.

It works I’m happy with it

Recently moved into a home with a very cramped plenum (doohickey above the air handler that disperses the air through various ducts). Somewhere in that is a hard angle or two which makes the air really reverberate through specific ducts in my basement.Since it is fairly impossible to get to the actual source of the noise, I *luckily* happened across the neverest insulation silencers. They're a very simple idea: round squishy "foam" that you shove into your round ducts. These foam inserts have a number of cutouts in them so you can choose how much air to let through vs how much noise to bounce back down the duct.Yeah, it cuts down the air a bit coming out of the duct. But, it's well worth it - I no longer feel like I have the cheap seats in an airplane next to the freaking engine. Installation was simple: pull out a few of the cutouts on the foam inserts, remove the register, shove 1 or 2 in there, replace register.

They help with the noise a bit, the price is a bit high for what they do.

I did not notice any muffling or dampening of the sound, even with several plugs installed.

I had a return duct that was connected via pipe to the return duct near the fan in the bedroom. The air noise was quite loud and very noisy since it was in the bedroom. I placed 2 of these insulators in the duct and the results are outstanding! The duct noise is hardly noticeable and the air flow is adjustable. Highly recommend!

La verdad no reduce significativamente el ruido pero si reduce la cantidad de aire que entra a tu cuarto