This International Standard specifies the measurement method and conditions to obtain reproducible and comparable exterior noise emission levels and spectra for all kinds of railbound vehicles operating on rails or other types of fixed track, hereinafter conventionally called “unit”. This standard is applicable to type testing of units. It does not include all the instructions to characterize the noise emission of the other infrastructure related sources (bridges, crossings, switching, impact noise, curving noise, etc). This International Standard is not applicable to: — the noise emission of track maintenance units while working; — environmental impact assessment; — noise immission assessment; — guided buses; — warning signal noise. The results may be used, for example: — to characterize the exterior noise emitted by units; — to compare the noise emission of various units on a particular track section; — to collect basic source data for units. NOTE 1 The type testing procedures specified in this International Standard are of engineering grade (grade 2), that is the preferred one for noise declaration purposes, as defined in ISO 12001. If test conditions (e.g. Vehicle and/or track conditions, measuring conditions) are relaxed (e.g. as done for trackside monitoring of in-service trains), then the results are no longer of engineering grade. NOTE 2 The procedures specified for accelerating and decelerating tests are of survey grade, see ISO 12001. NOTE 3 Additional guidance is provided in Annex D for measurements in the specific case of light rail vehicles.