As a local resident, perhaps I can shed some light on this particular noise issue:
1) The SOUND Transit tracks are on a long elevated structure in this area, always more noisy than ground level running. The structure is hollow concrete sections bolted together on concrete risers.
2) The SOUND Transit trackage is alongside East Marginal Way South, a busy truck route & access route to a Metro Bus Yard.
3) As the article states, the area is almost directly under the South Final approach( or occasionally takeoff ) from Boeing Field. All Boeing 737's make their 1st landing here for final outfitting; UPS, BAX & DHL also fly airfreight routes out of the facility. The Seattle P.D. shooting range is also on the road; Interstate 5 & S.R. 599 are within 1 mile.
4) This neighborhood of North Tukwila is rather rundown; I'm not sure property values can go much lower, unless the Duwamish River starts flooding. ( A distinct possibility, as the Howard Hansen Dam upstream is leaking. )