Does anyone have a suggestion or an idea for sound insulating outdoor HVAC equipment? Currently we have approx. 25 tons of equipment placed inside of a wooden fence enclosure with a wooden trellis on top. Our idea is to line the fence with some sort of sound absorbing material but we are having trouble finding one that works for exterior applications. While these units are not putting out a tremendous amount of noise the idea is to get it low enough that people passing them on the sidewalk, which the sit directly next to, do not notice a change above the ambient sound of the street.
Sound absorptive panels are available in various forms, but only partially reduce sound. Your post indicated elimination to the level of ambient at a nearby walk. From my past experience, this is only realistically achievable by use of heavy mass walls (i.e. masonry) that are at least 3 or 4 feet taller than the equipment. Even then, some crossover noise can be heard.
An overhead covering is not always necessary. If there are no nearby hard surfaces that are angled such that they reflect sound back to the ground, the top can be left open and very little sound will be evident at the adjacent walk. Any door, crack, or other opening in the wall will allow sound to pass around or through the material.
Many of the newer central chillers have noise levels below the current volume standards, but the frequency is much higher than older equipment and seems to be in a range of human hearing that is extremely annoying. We have retrofitted masonry walls around several of the newer replacement chiller units. We had tried light-weight sound panels but they proved to be only partially effective.