A sonic umbrella was a device° used by Missy aboard a Mondasian colony ship during the battle. The activation controls were located at the handle end opposite the emitter at the tip. Missy had a tendency to dance with it when hearing music.
It had multiple uses, namely how Missy used her umbrella to locate and call up a lift on board the Mondasian colony ship, (TV: World Enough and Time / The Doctor Falls) locate the hidden lifts and shuttles found on Floor 0507, lock said lifts to stay on the desired floor, close a metal door several feet away and could combine with the Twelfth Doctor's sonic screwdriver to create a barrier to hold a fully evolved Cyberman back while the Master (using his laser screwdriver) and a cyber-converted Bill Potts disabled it. The umbrella could also be used as an effective melee weapon; Missy used it to strike the Doctor to the floor shortly after he gained an advantage over her younger self, and to briefly knock the Master out with a blow to the head. (TV: The Doctor Falls)