A small selection of calculation methods is presented here.
The Preliminary calculation method for Road Environmental Noise (VBUS) can be used to calculate the noise indices required for noise mapping. The equivalent continuous sound level is calculated for each period. In addition, a weighted 24-hour value, the day-evening-night noise indicator LDEN, is determined. Supplements are taken into account for evening and night times; 5 dB(A) are added to the evening index and 10 dB(A) to the night index (see formula).
After some (provisional) national solo agreements and transitional provisions, see VBUS, a Europe-wide uniform assessment method was established with the "Commission Directive (EU) 2015/996 of 19 May 2015 on the definition of common noise assessment methods pursuant to Directive 2002/49/EC of the European Parliament and of the Council as amended on 10 January 2018". This must be applied as of 2019 for noise mapping. The directive and the valuation model are the subject of an intensive scientific discourse (cf. https://www.researchgate.net/search.Search.html?type=publication&query=cnossos-eu). Read something here to understand the arguments.
Have a look at this dB-Calculator for a Calculation of road traffic noise