Relating short-term noise measurements to the L_den indicator

The L_den indicator is the chosen noise indicator to be used in the presentation of noise maps to comply with the Environmental Noise Directive, directive 2002/49/EC. As L_den represents a yearly average noise level it is not possible to directly compare short-term measurements with results displayed in strategic noise maps, meaning impartial public validation of noise maps will prove difficult. This paper investigates a relationship between the two quantities by evaluating the typical variation in noise patterns throughout a time period representative of an average year. Initially noise maps were developed using standard noise prediction software and predicted results were displayed in terms of L_den. A measurement campaign was then initiated which involved the recording of short-term measurements in various locations, along with fixed long-term measurements. Thus it was possible to determine how predicted maps compared with a variety of different scenarios e.g. different times of day, different meteorological conditions, etc. In this way it was possible to provide guidelines to the general public, which may be used to independently validate noise maps displayed in terms of L_den through the use of short-term measurements.