Monitoring and Measurement methods
Imagine Deliverable D5
This method describes how to determine Lden and Lnight, as defined by the Environmental Noise Directive 2002/49/EC, by direct measurement or by extrapolation of measurement results by means of calculation. The measurement method is intended to be used outdoors as a basis for assessing environmental noise and for verifying the quality of predictions. The method can also be used for monitoring purposes.
Description of the Work Package
The IMAGINE project deals with both prediction methods and measurement methods. WP 3 has been assigned the task to draft standardised test methods for measurement of Lden and Lnight for road, rail, aircraft, industrial noise, in the format of EN ISO standards, each referring to two parts, viz.
- Measurement during long time intervals up to at least one year,
- Combination of short time measurements and computation
The background is that the Environmental Noise Directive 2002/49/EC requests member states to map environmental noise, to report the results and to establish action plans. The basis is Lden and, occasionally for sleep disturbances, Lnight. These levels will in the future be determined using harmonized prediction methods, which are now under development in the Harmonoise and Imagine projects . Although it is foreseen that such calculations will dominate over measurements there is still a need to carry out measurements using harmonized methods. The objective of such methods is to check the conformity of computed maps with the real levels, to validate prediction methods, and, in some very complicated cases, to replace calculations.
It is difficult to measure Lden. A true Lden measurement requires a measurement time interval of at least one year. Real measured levels could either be due to single sources or include different noise sources like road, rail and aircraft noise as well as noise from industrial sites, private household sources, temporary construction sites, etc. It is necessary to separate these sources and as the noise maps are based on the long-term Leq all "extraneous" noise from temporary sources (e.g. construction sites) has to be identified and excluded. Examples of quantities which may have to be determined automatically are hourly Leq, L95, L01,Ěspectral information (tonal penalties), automatic impulse recognition and counting, level-time records, source identification (statistical methods, etc.) and meteorological parameters like wind speed, wind direction, temperature, rain and relative humidity. The hourly Leq will be the basic parameter to calculate for example Lden. L95 and L01 are necessary to assess background levels and "peak" levels. Level-time recordings are of particular interest for aircraft noise but may also be useful for other types of sources.