Have you changed the anti-freeze evey 2 years. If you have not you may have a coolant system problem. It sounds like the water pump may be going bad but unless the mileage, 11000, is a typo that might not be the case. Regardlesss, anti-freeze being neglected is one of the top issues that I see customers have as people tend to not change it every 2 years or 24000 miles. It can become a conaminant and make sensors not work properly causing fans not to come on temp gauges to read incorreclty, and possibly harm water pumps.
The first thing to do is service your anti-freeze if you have not as it only costs about $30 maximum to change it and get a new radiator cap. Then get a coolant system pressure test done to ensure your system is okay. If the noise persists you may want a repair shop to see if you need a new water paump.
Take note of your coolants condition when replacing and flush out the system.