AMD Radeon HD 6870 Graphics Card Acoustic Tests
 

The reference cooler attached to our HD 6870 sample was very quiet when idle, measuring 15 dBA@1m in our test system, only a few dB higher than our anechoic chamber's noise floor. Like most high performance cards, it runs hot and loud on full load. If you only care about the noise level of the card when it's sitting idle, you can stick with the stock cooler. Otherwise it is a perfect candidate for an aftermarket heatsink.

http://www.silentpcreview.com/amd-radeon-6870