# Mapping Noise from Motorised Transport in the Context of Infrastructure Management
## 2 Materials and Methods
### Description of the Calculation Model Calibration Methodology  
For the verification and calibration of the computational model, measurements were carried out using the sampling method by point G (a height of 4.0 m \(\pm\) 0.1 m) of the reference methodology, recording the value of the equivalent continuous A-weighted Sound Pressure Level at representative noise emission intervals. The number of measurements in each representative measurement interval taken of not less than three and with a duration of at least 10 min depended on the gap between the extreme results of these measurements. If the difference between the results of the individual measurements is greater than 7 dB, the duration of a single measurement is increased to a minimum of 15 min. The value of the acoustic background level was determined as far as possible when the source noise was not emitted, and if this was not possible, using the L95 index.  
Calibration of the computational model was carried out concerning the results of noise measurements and vehicle traffic recorded during the study. The calibration process sought to minimise the error resulting from the difference between the measured sound level value and the value derived from the calculation model. During the calibration process, corrections were made to parameters determined with the most significant uncertainty, e.g., parameters relating to the type of road surface and ground absorption coefficient, G.  
The calibration started once all complete data had been entered into the computer model, including the following:  
* Complete geometry of the individual road sections,
* Traffic volume and vehicle speeds observed during the noise measurements,
* Type of pavement--based on visual inspection,
* Geometry of shielding, attenuating and reflecting objects,
* Elevation model of the area.  
Irrespective of the measured sound level, either a single measurement result, \(L_{zm}\), or a set of n values is available for comparison with the calculation results. In the second case, the average value used in the calibration procedure is determined from Formula (2):  
\[\text{L}_{zm}=10\cdot\log\left[\ \frac{1}{n}\sum_{i=1}^{n}10^{\frac{\text{L}_{zm }}{10}}\right] \tag{2}\]  
Validation is a process designed to address the degree of agreement between model predictions and the actual value. Specifically, validation refers to the methodology used to evaluate the accuracy of the calculation method, where accuracy is measured by the error (the difference) between the calculated and measured sound levels. The outcome of the validation procedure is the determination of a so-called calibration correction for the computational model (a value-added or subtracted to the result of the calculation or the emission level of the noise source, depending on the software used), introduced to increase its accuracy. If the calibration correction falls within the acceptable range (meetsthe established criteria), then the model and its predictions can be considered valid. The minimum value of the calibration correction is determined in a procedure referred to as calibration or adjustment of the acoustic model parameters to obtain the best agreement with the measurement result. Table 5 compares the measured results with the results obtained by calculation.  
Based on the calculations performed, it is concluded that the prerequisite for calibration has been met.