Download a program like MSI Afterburner, and create something called a custom fan profile. Make sure your temperatures are in a safe range before attempting this. By creating a custom fan profile you can choose how the fan reacts to specific temperatures. What you would be doing is lowering the fan speed gradually, starting out high (to make sure you don't damage your card), and then you test the fan speed and temperatures with a game or benchmark. Keep a close eye on your temperatures. If they are fine, then lower the fan speed in the fan profile and repeat the process.
Open your case, and make sure your cable management is good. Also clean out any dust from your case, and the graphic card.
Which 560 Ti to be exact that you have, making the fan speed lower isn't always the best idea as it will allow the vram and power vrm on the card to overheat. You could look into a low cost diy liquid cooling loop just for the card or going aftermarket for the cooler.
Larger high cfm low rpm fans will allow for low noise but decent performance cooling.