Reference sound source for sound power measurements. Norsonic’s rugged and compact design makes it well suited for both laboratory and field use. The design ensures a stable and uniform sound power output with unique long-term stability. The reference sound source Nor278 is designed to produce a stable and uniform sound power output with unique long-term stability. The high sound power output makes it ideal for sound power measurements in a noisy environment. The rugged, but yet portable and light weight construction is perfect for field us as well a laboratory use. Every effort is made in the design to ensure a uniform frequency response and optimum directional characteristic well inside the requirements in ISO 6926:2016.