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); and

— 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.