Hi, did you try turning the buzzer off with the knob on the right side of the operation panel (which is also used as the start button)? If you turn that knob to the left, it should turn off the buzzer.

If it still buzzes, the switch behind that knob may be faulty. You can get at it by removing the panel at the rear of the dryer (6 screws) and then you can test it and adjust its internal contacts if need be.

Hope that helps!