Here i am, Mr. Negativity again.
Having worked in sound before, and understanding basic acustics...this really isnt muffling as much as it is decreasing the sharpness of the fan blades cutting through the air. Very similar to how a foamy on a microphone reduces the impact of P's and B's and other "putter" sounds from popping though the sound system. Essentially the foam absorbs the impact of the sound wave so the microphone diaphram sees less of an impact, but maintains the same amplitude. Same principle here. Its a plenum with a foam lining to disperce the sound wave, and then reduce the impact of it into the foam, making it less noticable to the human ear. So its not really "reducing" the sound trhough a noise canceling baffle system like you would see on a automobile muffler. Its just masking it, and throwing it down away from the users ear making it less noticable.
I think to honestly review this product, you need to have a db meter. Becuase while precieved loudness levels may decrese, i have a feeling that actual noise levels will be just as loud. Also, when you do get a db meter to test it. You should use a seperate PSU, hot wire the ATX connector, and run the PSU solo with no outside noise interference. Hell, you could even make your own little anechoic chamber with a carbboard box and some egg crate foam. But anyway...
Plus it would be interesting to see how much the case temps increases, if at all, with this product installed on a case reguardless of sound levels.
Unfortunately i think its kind of a gimicy product. And will do more to insulate my system from proper cooling then it will for reducing noise. In which case i dont think the trade off is worth it.
Also, whats the suggested MSRP on this product? Typically speaking Silverstone products tend to carry a premium price on them. And if the cost is $20 or above. It begs the question of actual value. Becuase at $70 for a PSU plus a $20+ exaust widget, you could buy quient design PSU, or for a couple bucks more, even a fanless truely silent PSU. So the value may not be there.
Id like to se a little more depth please.