Why is my skimmer pump noisy?

This could be the result of a few things, but keep in mind that all pumps of any manufacturer is going to make noise. Placement and surface that a pump is placed into can also affect the noise of a pump. If you have a hollow surface under the skimmer pump then it acts like a drum and will enhance the noise. You can use some mat materials to help dampen noise and vibration.

Take the pump apart and check that nothing has been sucked into the pump. Check the pin wheel impeller and make sure that no pins are broken off. Broken pins is a sign that something was sucked into the pump causing the pins to shear off. This will put the impeller out of balance and you will need to purchase a new one.
Clean the impeller assembly at least once every 6 months. Calcium will build up on certain parts and cause the pump to run harder which in turn will make it louder.
Check the shaft to see if it has broken. A broken shaft is another indication that something was sucked into the pump. The pump will still run but everything will be out of balance and make a lot of noise.

Make sure you have the air hose attached to the silencer. Pumps are also will be a bit noisy for the first 2 weeks of initial operation.