There are a few things that can cause your central vac to be so loud. One of the most common causes is blocked air filters. When these filters become clogged, the vacuum cleaner will have to work harder to create enough suction to pick up debris. This results in increased noise and wears on the motor and other parts of the machine. Another common cause of loud central vacs is incorrect installation. If your central vac is not properly grounded, it can generate an excessive amount of electrical noise. This noise can be heard even when the unit is turned off and can damage electronic components over time. If you notice that your central vac is making a lot of noise, it may be time to take it in for service or replace its filters. In some cases, replacing the motor may be necessary.