A:Answer Thanks so much for asking, Bess! There are two fans in the oven. The internal cooling fan, which helps keep the electronics cool, and the convection fan, which is visible at the back of the oven and circulates heated air for more thorough cooking. The convection fan turns on and off at regular intervalas and has a quiet, low humming noise. Some models have more than one convection fan. The cooling fan is not visible, but you will hear it running whenever the electronics get hot, and turn off when the electronics are cool. Either the oven or the cooktop can create enough heat for the cooling fan to come on. ^Jecca