The business of erecting barriers such as "soundwalls" along a freeway, to block noise, is perhaps trickier than it first seems. Three legacy pages [circa 1996] about noise, from the first mo'c Physics Applied website, are accessible on the left. They provide brief outlooks on some of the more interesting situations that are encountered.

There is also a link to a slide show on diesel exhaust particulate matter as a toxic air contaminant— as a source of quantifiable health risks.