Since 1992, the Metropolitan Airports Commission (MAC) has implemented one of the most comprehensive airport noise home mitigation programs in the world. By installing new or reconditioned windows and doors, central air-conditioning, wall insulation and vent baffling, the program reduces interior noise levels by a minimum of five decibels. In 1992, the MAC began mitigating homes against aircraft noise in the area defined by the 1996 65 DNL noise exposure map. Under this program, 7,690 single-family homes and 661 multi-family units have been mitigated at a total cost of more than $232 million. In April 2005, single-family homes within the updated 2007 65 DNL noise exposure map began being mitigated. All 156 homes are within the city of Bloomington and have been mitigated. An additional eight homes in the city of Richfield will be acquired at the request of the City. Several multi-family buildings (located in Bloomington and Richfield) are also eligible for mitigation under the 2007 65 DNL map. In 2007, the MAC voted to approve a proposed settlement in a noise mitigation lawsuit brought by the cities of Minneapolis, Richfield and Eagan. Under the new noise mitigation program, the MAC will provide mitigation to homes in the 60 to 64 DNL contours. Mitigation activities will vary based on noise contour, with homes in the most noise-impacted contours eligible for more extensive mitigation than those in less impacted areas. Multi-family dwellings (those with more than three living units) will receive less extensive mitigation than single-family homes.