Do our ears or brains gradually adapt to noise pollution?
This is a fascinating case of sensory adaptation and neural adaptation. Another example of this would be when you stop smelling something after being exposed to it for long periods of time (as you probably know, this "long period of time" happens to only be a few minutes). A great representation of this happening with the nerves in the skin was done by Georg Meissner:


This image is from https://www.boundless.com/psychology/textbooks/boundless-psychology-textbook/sensation-and-perception-5/sensation-37/sensory-adaptation-160-12695/

When stimulus is applied, these nerves begin rapidly sending messages to the brain in the alarm period. The rate of these signals slowly start to decrease over time in the resistance period until they finally reach exhaustion and stop completely in, of course, the exhaustion period. Keep in mind that the time it takes for all this to happen varies greatly upon what type of cell it is (obviously olfactory cells have a much shorter exhaustion time than, say, hair cells (hearing cells)). After these cells have had a chance to recover (more like recalibrate actually), we can begin to hear/smell/feel/taste again.

I hope this helps.