Very silence cpu cooler

I have a Zalman CNPS10X Extreme and I quite like it. Works well, looks great and it's quiet. The "CNPS" stands for "Computer Noise Prevention System" so they're trying to make really quiet coolers. This one I have set to Auto with the maximum threshold of about 2280rpm. It generally is very very quiet at around 1000-1600rpm and only under max usage does it ever get somewhat loud.

The Noctua NH-D14 is good, don't know how loud it is.

Scythe Mugen 2 rev. B is good.

Coolmaster V8 is good.

Of those, you'll probably want to check reviews for loudness. Pure performance I think the Noctua is best.