living next to a freeway

I don't know the statistics, but it's probably safe to say that in the US, a large percentage of the population lives within a mile of a major freeway. I grew up next to the Long Island Expressway. Now I live a stone's throw from the 101.

It occurred to me recently that, unlike the arrangement in Old Westbury, NY, where the murmur of the expressway was a nearly round-the-clock ambient accompaniment, I don't generally notice the sound of the 101. Could it be that the river somehow "absorbs" the noise?

Stranger still... No sooner did I start pondering why I wasn't hearing the freeway, than I suddenly did start hearing it. Of course, that was during a long holiday weekend, and there was almost certainly more traffic.

Since then, I notice the sound of traffic some of the time.