Consequence of the noise maps of the railway

Hello everyone. I have a question and hope that someone can tell me something. Unfortunately, I can't find anything about it on the internet. I am interested in a plot of land where there is also a development plan without major building regulations. Now, even before buying the plot, I have already requested the costs for a bungalow from various construction companies. Despite the development plan, I was informed that due to the noise maps from the railway, they would be obligated to build with a noise protection level 4. Is that so? Do the railway noise maps, which were only created by calculation, have such an influence on the building regulations? But shouldn't that have been stated in the development plan? Who can help, I am now unsure about buying the plot because noise protection level 4 is expensive and actually the railway is not so loud there when you stand on the plot.

Facing a similar problem, also a railway line, but the development plan requires soundproofing according to DIN 4109 (noise level range III) by 35dB.

Noise can potentially make you sick. When standing around on the property in an anticipatory mood, judgment is sometimes impaired. Build Stage 4 or look for another building plot, the latter would be my favorite.