They do reduce higher frequency echoes somewhat. Being as shallow as these are they won't have much impact on lower frequencies, and I feel some 80 mm deep panels I also have are more effective. Anyway, I wanted to dampen high frequencies in an area of my home studio where space is scarce, thus I didn't want panels to stick into the room. They certainly helped.
From doing research, this foam sheet seems to be very good for the price. I was expecting it to be smaller for some reason, although it is a good size. You would only need a few sheets to cover most of a reasonable sized wall.
It seems thick enough to me and I have noticed a lot of rehearsal rooms and studios have this particular foam. It's easy to cut to fit whatever your needs. I have definitely noticed the difference in the room from using this. I only have two sheets spread across a reasonable sized room. Although, I would consider getting a few more if the room was being used for recording. Does the job for rehearsals.
I would highly recommend this product, as the price is very good, considering the alternatives. You won't go wrong with it.
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