Murata's piezoelectric sounders are suitable to be used for smart door lock (a system that manages the locking of doors by using a smartphone app or other device that is widely used in the doors of rooms, entrances, and other openings in hotels, accommodation facilities, offices, homes/apartment buildings, and other structures) operation confirmation sounds and lock confirmation feedback sounds. In addition, smart door locks driven by cells, batteries, or other devices require low power consumption. Accordingly, Murata's piezoelectric sounders that contribute to long life are ideal. We introduce here piezoelectric sounders this time.