ISO 3381:2021

This document specifies the measurement method and conditions to obtain reproducible noise levels on-board all kinds of vehicles operating on rails or other types of fixed track, hereinafter conventionally called “unit”, except for track maintenance vehicles in working modes.
This document is applicable to type testing. It does not include all the instructions to carry out monitoring testing or evaluation of noise exposure of passengers or drivers over a whole journey.
This document is not applicable to guided buses.
It provides measurement procedures for vehicle interior noise (in general, a vehicle type test is carried out using only a selected subset of these tests):
—    when the vehicle is moving at constant speed;
—    when the vehicle is stationary;
—    when the vehicle is accelerating or decelerating;
—    in the driver's cab when an external warning horn is sounding (specifically required for European Union regulation application)
It does not provide measurement procedures for:
—    audibility or intelligibility of any audible signals;
—    assessment of warning devices other than warning horns.
The assessment of noise exposure of train crew due to operational conditions is not in the scope of this document.
The results can be used, for example:
—    to characterise the noise inside these units;
—    to compare the internal noise of various units on a particular track section;
—    to collect basic source data for units.
The test procedures specified in this document are of engineering grade (grade 2), the preferred grade for noise declaration purposes as defined in ISO 12001. If test conditions are relaxed, for example as they are for monitoring of in-service trains, then the results are no longer of engineering grade.
The procedures specified for accelerating and decelerating tests are of survey grade (grade 3).