Notwithstanding any general or special law to the contrary, the Massachusetts Bay Transportation Authority is hereby directed to conduct a comprehensive sound study along the Red Line extension to Braintree, so-called, from the Neponset River Bridge to the Braintree Red Line Train Station, to determine the ambient noise level, using the background A-weighted sound pressure levels that is exceeded ninety percent of the time measured during equipment operating hours over a minimum of a twenty-four period, less the noise generated by the existing MBTA trains. Said study shall be conducted by an acoustical engineer employed by or on behalf of the MBTA. In those residential areas where the decibel level generated by the Red Line trains exceeds the ambient level by ten or more decibels, the MBTA is hereby ordered and directed to install sound barriers in order to mitigate said noise pollution problems.

Said barriers shall be of a design approved by an acoustical engineer hired by or employed by the Transit Authority. Said design shall then be approved by said Authority and local Board(s) of Health(s) Departments after a public hearing process.