I think a few people have asked this and I have not seen an answer posted here.
As I wanted to do this I found a guide to set Rivatuner to create a profile based on temps.
I found even 100% fan speed wasn't excesivly noisy on the reference cooler, and certainly won't be noticed while gaming, so I have set mine to run at 75% up to 57 deg, 85% between 57 and 65, 90% between 65 and 70 deg, and 100% over 70.
I have found gaming for 3 hours solid, temps settle at around 72 deg and don't get any worse, so I am quite happy with that
Linky
As I wanted to do this I found a guide to set Rivatuner to create a profile based on temps.
I found even 100% fan speed wasn't excesivly noisy on the reference cooler, and certainly won't be noticed while gaming, so I have set mine to run at 75% up to 57 deg, 85% between 57 and 65, 90% between 65 and 70 deg, and 100% over 70.
I have found gaming for 3 hours solid, temps settle at around 72 deg and don't get any worse, so I am quite happy with that

Linky