I think I'm rather tolerant of fan noise, but find the NF-F12 fan is an annoying little thing. I sit about 1.5m from my PC, and 70% is about my limit for them with a little music playing. With no external sounds, definitely a little lower.
Since the cooler's performance is acceptable, play with the fan curve in bios first. Following example is from an Asus bios, so yours might not look the same:
Cpu Upper Temperature: 75C. You can try a higher value, but your board may invalidate it, and give you the highest possible it offers.
Cpu Fan Max Duty Cycle(%): 100%. I don't think it does much good to set this one lower than that. At least on my board, if it crosses, I think 80C, the mobo ignores fan curves and runs 100% until temperature drops below that.
Cpu Middle Temperature: 70C
Cpu Fan Middle Duty Cycle(%): The highest you're comfortable with. If it's 50%, then enter that.
Cpu Lower Temperature: You might be able to enter the same value as middle, so try it.
Cpu Fan Min Duty Cycle(%): Try the same as middle.
If done like that, the fan should stay at whatever you set it at, all the way up to 70C.