What Is A Good Dba Fan When Looking At CPU Heatsinks And Fans How Quiet Should A QUALITY Product Be?

When looking at CPU heatsinks and fans how quiet should a QUALITY product be? - what is a good dba fan

I am seeking a Zalman CNPS9700 LED 110mm CPU Cooler Ball 2, which was pretty good reviews, but I want is a little quieter than the range of values, but it remains cool and comfortable. I know that I sound as close to possible to 0 dBA, but what are some realistic meauremnts a quality product?