BS EN 17285:2020 pdf free.Railway applications一Acoustics一Measuring of door audible warnings. BS EN 17285 Each component of the instrumentation system shall meet the requirements for a class 1 instrument specified in EN 61672-1.The sound calibrator shall meet the requirements of class 1 according to EN IEC 60942.Microphones with free-field characteristics shall be used. A suitable microphone windscreen may be used.Where one-third...