NOSE CONE DEVICE AND BUILT-IN CALIBRATION CHECK AS ESSENTIAL FEATURES OF A STAND-ALONE INSTRUMENT FOR UNATTENDED MID- AND LONG-TERM NOISE MEASUREMENTS

Environmental noise generated by ground transportation, construction sites or recreational activities, is coming from all directions, and such multiple sources are usually located at random positions with respect to the measurement point With the instrument placed vertically (while sources mainly coming from a reference direction of 90 degree from its axis), the goal is to meet the requirements of the IEC 61672-1 standard [1] on sound level meters taking into account noise incidence from the horizontal direction. Emphasis will be given on the main technical difficulty and the adequate solution meeting the standard requirement.