In addition to mainstream research, which is delving into new materials and sound deadening techniques, a discovery in the Mexican ruins at Chichen Itza may yield exciting possibilities. Martin Palmer notes that California engineer Frank Hodgson of the Kilo Foundation is investigating these ancient Mayan ruins, in which the configuration of some stone stairways appears to convert the frequencies of impinging sound waves upward. Departments of Transportation in several states, including Washington, are looking closely at Hodgson's research because it seeks to change noise patterns altogether, rather than imperfectly reflecting, deflecting, or absorbing the sound waves. Built of wood, stucco, concrete, masonry, metal and other materials, these walls have limitations. Openings for driveways or intersecting streets will destroy the effectiveness of a sound wall.
Noise mitigation can be a tremendous secondary benefit of freeway lids.
This solution is very expensive, however, and may not compete well with other needs for scarce transportation funding. Because the pavement has a tendency to break up under heavy use and can lose its special ability over time applications may be limited. Sound Isolation in the Heavily Built Environment Airport noise affects millions of people throughout the United States. Significant reduction in aircraft noise, itself, rests with airplane engine manufacturers. Through aggressive abatement, however, sound isolation is an area in which environmental architecture can play an important role.