I would not recommend the Whisper HOB if you want a quiet filter. I had an internal Whisper that was quiet but didn't filter much. I bought a Whisper 30 HOB and it was noisy from day one. After checking the reviews on line, it seems that most of them are loud. I tried everything to quieten mine down. I gave up and bought an aquaclear. The Whisper did filter just as well as the aquarclear though. The noise was irritating.
Interesting thing about Tetra...this company used to be, "back in the day," the Rolls-Royce of aquatic hobbyist products...I mean, all their products were well-regarded and their original Whisper filter line was
the HOB to have...
Today, it's just not the same -- from what I have heard and read, these "newer" Whisper filters, including the "EX" series, just don't cut it especially when compared to the AquaClears, etc. There was a time, years ago when I kept tropicals with my dad, that I wouldn't use anything other than Tetra even for food (their TetraFin/Min flakes were always at the ready), but now I avoid most of their products like the plague as the whole operation seems to have gone really mass-market in terms of approach...
This happens not only with aquarium hobbyists and related products, but in other commodity sectors as well -- take, for example, the "Rockford Fosgate" car audio manufacturer. Was a time when you couldn't touch this stuff unless you were really wealthy; as soon as I saw their amps and speakers showing up in the Crutchfield catalog, I knew they had gone "mass-market" and that it was pretty much over....however, in Rockford's case, they still do make a great car stereo product and not that Tetra doesn't make at least decent stuff, it's just not the same as it once was...