Engineers have found that wetlands, grassy fields and soil or sand filters can take in stormwater with different levels of pollution and release water with a relatively constant cleanliness.
VOA: standard.2010.08.04
But speaker systems to date have annoyed everyone, employees especially, with their constant, ubiquitous noise pollution.
We can and should control surface pollution as that effects air quality yet there is a huge difference between controlling air quality as that remains constant in cold or warm environments while temperatures constantly fluctuate from day to night, month to month and year to year, in the Western isles of Europe we are having a particularly cool and wet summer.