I'd really like to see a technical analysis of this project - I've checked the usual spots (JASA, INCE Journal, Journal of Sound & Vibration, etc) and couldn't

I'd really like to see a technical analysis of this project - I've checked the usual spots (JASA, INCE Journal, Journal of Sound & Vibration, etc) and couldn't find anything. Google searches just lead to Paul De Kort's writeup, and similar articles. A little background about issues involved: if you have a noise source on (or just above) the ground, and a receiver on (or just above) the ground with line-of-sight to one another, there are three paths that noise can take from the source to the receiver: 1. The source can emit sound that goes up into the atmosphere, but under certain atmospheric conditions, that sound can be reflected back down to the receiver. 2. The sound travels directly, in straight line, between the source and receiver. 3. The source emits sound that travels downward at a shallow angle into the ground, and is reflected up to the receiver. For path #3, if the ground is acoustically "hard" (generally meaning non-porous), the reflected ground path adds to the noise heard at the receiver. If the sound is acoustically "soft", generally porous, the sound is absorbed [0] so the reflected sound does not add to the direct sound, and the resulting total noise is quieter compared to the situation with hard ground. This explains the reduction in sound level when the land was plowed - the hard ground (dense, packed soil) was transformed into soft ground (loose, tilled soil). This also explains why background noise levels drop when snow is on the ground. It looks like the Schiphol landscaping addresses mostly #3, possibly #2 (by blocking direct LOS between the source and receiver). This is interesting, but the same can also be achieved by a noise wall at the airport taxi and run-up areas (which is the typical solution), or creating a wide, dense tree belt. The claim is that spacing the berms by the wavelength of the (presumably dominant) airport frequency creates greater reduction, but I'd really like to view technical data to see how well that works. The articles claims the berms have "reduced noise levels by more than half" - is that in terms of sound pressure, sound power, or sound perception? If sound perception, that's ~10 dB and that's really impressive. If sound power, that's around 6 dB, which is decent. If sound pressure, that's 3 dB, which is strictly in the "meh" category. [0] Technically the sound isn't absorbed, it goes through a phase change so that the reflected sound cancels out part of the direct sound.