Fascinating stuff! Thank you for posting.
I am involved with a number of horizontal drilling locations that either are inside cities or the cities are encroaching on us. When you frac a well (and just drill a well) there are huge diesel generators (and pumps, and well, a giant drill) that humm along for a year.
Our noise is usually within a pretty fixed frequency range, so we've done a lot to address this. Generally giant berms of dirt to reflect sound "up", coupled with large hanging helmholz panels several stories tall.
When the production phase is over, it's berms, some fixed relectors/resonators, coupled with natural absorption -- I like to plant Afghan pines and Texas live oaks (both keep their leaves all year and don't particularly require watering after being established after a year). The pines are soft wood and the oak hard and do very different things to sounds. But a triple row of mixed species does a lot, both in keeping things looking nice and absorbing the periodic banging of metal and trucks doing their thing.
We have several in residential neighborhoods. It looks like a nice greenspace.
Planting buffallo grass also helps (a very tall native grass in west Texas, almost a bamboo) -- and it attracts a ton of wildlife -- unfortunately also rattlesnakes, which, in turn, like to hang out on concrete pads under warm diesel engines or cool metal sheds, depending on the time of year.
So that's a rather tough sell to workers. LOL. Don't blame them.