The drain pump makes a buzzing or humming sound when it forces the water down the drain. The drain pump runs several times throughout a normal-length wash cycle, and the buzzing noise will occur for several seconds each time. However, if your dishwasher is sound-insulated, you are less likely to hear this noise.
Some Whirlpool dishwashers come equipped with a motorized switching device that makes a grinding or buzzing sound when the dishwasher changes to pump-out mode. The device is located behind the control panel, where the sound usually originates in most cases.
Disposal Is Running
If you have a garbage disposal, then your dishwasher is probably connected to it via a soft food disposal unit that breaks up the chunks of food into smaller sizes for entering into the plumbing system. This unit often makes a buzzing or whirling noise as it grinds up the food. You may notice this noise several times during a normal wash cycle.
A sudden buzzing or vibrating sound during the beginning of the drain cycle is probably a phenomenon known as “water hammer,” also known as hydraulic shock. This phenomenon is caused by a valve, the one connected to a faucet-like pipe, inside the dishwasher suddenly closing. The after-effect, known as the water hammer, sends a shock wave of water up the plumbing. This shock wave can cause damage to both the dishwasher and the plumbing. However, there are devices you can purchase that will help prevent this from happening.
If the buzzing noise persists throughout the washing cycle without stopping, call Whirlpool customer service to schedule a service check of your dishwasher. When the buzzing sound starts, pause the washing machine to check if the noise continues even without the machine running. If it continues, then the dishwasher may need to be serviced.