The primary purpose is to ensure the accuracy of measurements of sound intensity applied to the determination of sound power in accordance with ISO 9614-1. Specifies performance requirements for instruments used for the measurement of sound intensity, and their associated calibrators. The requirements are intended to reduce to a practical minimum any differences in equivalent measurements made using different instruments, including instruments comprising probes and processors from different manufacturers. Only applies to instruments which detect sound intensity by pairs of spatially separated pressure sensing microphones.