Yeah, it didn't seem to take much to make it loud. I got rid of the sand in that tank after only about a month due to the noise. But, I figured it probably had something to do with having such a big filter on a little tank. At the time, the Penguin 350 was on only a 20 gallon, so even with the intake tube shortened as much as possible it was still pretty low.
After the sand thing that filter never seemed to get as quiet as it once was, but it still gave me another 5 or so years of service. In fact, it just stopped working about a month ago and that is when I decided I would invest in a new internal filter, and better canopy, and then I screwed up my cycle and replaced my gravel with sand. lol
But, I think I could still get some more use out of that Penguin. If I throw my impeller for my Top Fin filter in the Penguin the filter still works, it is just really loud. So I think if I get a new impeller it'll still work. So, overall, I think the Penguins are decent filters. But, I don't have much experience with other types.