Reduced air flow can put additional stress on your motor, causing a change in it's sound. Make sure the pre-motor and post-motor filters are clean. Also check the hose for possible clogs. Except for the Multi-Layer Post Motor Filter, all filters can be washed in mild detergent. Allow them to completely dry prior to using them. The Multi-Layer Post Motor is replaceable but not washable. To relieve clogs in the hose, completely remove the hose from the back of the machine by the two screws and using a broom stick handle, push any dirt or debris to the other end and remove it. Located at the foot of the machine is a small curved hose. Release the screw holding this hose in place and remove any dirt. If these suggestions have not reduced the noise level, please have your machine inspected at a local BISSELL Authorized Service Center. BISSELL provides you with a one year warranty on this machine. This warranty does not include cleaning or removing clogs. There will be a charge for this service. To locate your nearest BISSELL Authorized Service Center, go to the BISSELL Homepage at: http://www.bissell.com. Select the Customer Support tab at the top of the page and enter your zip code in the search box. You can also locate a Service Center by phone, 24 hours a day, by calling 1-800-263-2535 and choosing option #2.