This disposal is very quiet, however not the normal way to operate. It has a built in switch that covers the drain. You must load the disposal, then install the lever (switch cover) that closes the drain and allows one to turn the disposal on and then it operates beautifully and quietly. Now, if you want to add more stuff, you must remove the lever, fill the disposal, replace the lever, and turn to operate again. It’s definitely safe, quiet, but a pain to have to remove and replace the lever each time. Then to have pure water drain, find the position of the lever to allow water to flow.
The old, leave it open, use the wall switch is more appropriate and customary for this kind of operation.