This document specifies two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer:

• the first method, called "steady-state mode”, is intended to evaluate the noise level under steady state flow, i.e. constant upstream pressure (steady-state test according to ISO 6358-1);
• the second method, called “discharge”, is intended to measure the noise level during the decrease of the pneumatic pressure (discharge test according to ISO 6358-2).

This document is applicable to pneumatic exhaust silencers and devices designed to reduce the sound produced by discharges of compressed air, entering in the scope of application of ISO 6358-1 and ISO 6358-2.