ISO 13325:2019

This document specifies methods for measuring tyre-to-road sound emissions from tyres fitted on a motor vehicle under coast-by conditions, i.e. when the vehicle is in free-rolling, non-powered operation. This is typically achieved by putting the transmission in the neutral or equivalent position and switching off the engine as well as all auxiliary systems not necessary for safe driving.
This document is applicable to passenger cars and commercial vehicles as defined in ISO 3833. It is not intended to be used to determine the sound contribution of tyres of vehicles running in powered condition nor for the determination of traffic sound nuisance at a given location.