This is a polygon dataset of the strategic noise mapping of agglomeration industry for Round 4 (2022), representing the situation during 2021, in the form of noise contours for the Lnight period. The dB value represents the annual average Lnight indicator value in decibels over the night time. The values are calculated at a height of 4.0m above local terrain, not measured, and should be treated with caution when looking at specific locations. The strategic noise mapping of industry was undertaken by Noise Consultants Limited inside the three noise agglomerations, under contract to the agglomeration local authorities. The outputs of the Round 4 noise mapping exercise were generated using a new common noise assessment method for Europe (CNOSSOS-EU), as set out in the revised Annex II of Directive 2002/49/EC, and they are not directly comparable to any strategic noise maps previously generated under Rounds 1 to 3, as these revised methods calculate noise emissions, propagation and residential population exposure differently from the methods used in previous rounds. The noise maps are the product of assimilating a collection of digital datasets, and over the last 15 years there have been ongoing significant improvements to the quality of the digital datasets describing the natural and built environment in Ireland, therefore the Round 4 strategic noise mapping includes changes to the model input datasets being used, compared to previous rounds, particularly related to the industrial areas modelled, the terrain model, building heights and ground cover. The strategic noise maps should not be relied upon in the context of planning applications for noise sensitive developments in the vicinity of the mapped sources.