I have the same machine and had a similar question. My machine had made about 6,000 coffees and although it has been desclaed about 20 times it's starting to sound tired. I rinse out the infuser every month and have replaced the o rings a couple of times.
My parents have just bought the same model and it sounds so much quieter than mine. I'm thinking I need to clean the grinder somehow. Have found a couple of products that should do this but haven't bought them yet...