PKM22 Piezoelectric Sounders Murata PKM22 Piezoelectric Sounders are externally driven pin-type speakers with sound pressure levels of 70dBA to 85dBA. PKM22 sounders feature a 22mm diameter, low power consumption, and have no contacts, providing no noise and high reliability. These Murata piezoelectric sounders are driven by a signal (2kHz or 4kHz) from an LSI and provide melodious sound. PKM22 sounders are used in digital watches, electronic calculators, phones, and other equipment.