The noise reducing equipment of the present invention is used in combination with a vertically oriented sound barrier wall to reduce the level of noise from a source of sound such as traffic generated on one side of the sound barrier wall and comprises an assembly composed of a predetermined number of interconnected resonant chambers mounted in tandem to said sound barrier wall in a relationship such that the assembly extends from said sound barrier wall on the side thereof opposite the source of sound with the resonant chamber closest to the sound barrier wall having a volumetric area larger than the volumetric area possessed by each of the other resonant chambers and an additional sound barrier section extending from the most distant resonant chamber relative to the location of the sound barrier wall. In addition, at least one external surface of the assembly should be coated with a photo-catalyst comprising titanium dioxide.