Considering Uncertainty When Performing Environmental Noise Measurements
نویسنده
چکیده
In general, estimates of uncertainties in measured values give an idea of the quality of the measurement. However with environmental noise measurements this is not necessarily the case since the variables affecting the measured levels can often not be controlled. Consequently an appreciation of the uncertainties in results lead rather to a better understanding of the measurement and its potential variability. In some cases, the uncertainty of an environmental noise measurement has to be properly quantified because it is needed to determine whether criteria or allowed tolerances in criteria have been satisfied. When monitoring legally binding boundary noise levels for instance, a high quality measurement may be required to ascertain whether or not a limit has been breached. Most practitioners engaged in the measurement of environmental noise will be familiar with the basic concepts of microphones and that they are designed to minimise effects induced by meteorological changes in temperature, humidity and pressure. They will be also familiar with the need to use a windshield when measuring outdoors. Measuring conditions are usually chosen for practical reasons that are not related to the limits of the instrumentation. One possible reason for ignoring the relatively small influence of weather on the instrumentation is the realisation that the weather has far greater effect on the propagation or transmission of noise. Obtaining measurement conditions that minimise the effect of changes in wind velocity, air temperature and humidity is by far a greater challenge to the practitioner. Three elements of any outdoor noise scenario are potentially affected by the weather. These are the noise source, the transmission path and the receiver. Of these the influence of the meteorology on the transmission path is least easy to determine. A recent study [1] into the sources and magnitudes of uncertainty identified the weather and changes in the weather as being one of the most significant influences on measurement uncertainties. This paper is concerned with quantifying these uncertainties, providing an overview of the meteorological mechanisms affecting sound propagation, and providing rules of thumb to give guidance when comprehensive meteorological data are not available when performing environmental noise measurements.
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تاریخ انتشار 2012