For extremely large projects, such as a new airport or freeway, it might be worthwhile to use a hedonic price model or a contingent valuation study to assign a dollar cost to the project's negative noise benefits. A new model or study will probably be required, because people in different locations value noise reduction in different ways.
A hedonic price model can show how traffic noise affects the cost of housing units. When creating a hedonic price model, use only actual housing purchases in the model, not simply the assessed value of houses. The model may need to use a different coefficient for noise depending on the location of the unit; people in rural areas often value quiet more than people in urban areas. The model can also use dummy variables to represent areas that value quiet more highly.
A contingent valuation study can show how much people value a percentage reduction in noise levels. However, the study must describe this reduction in terms that are easy for respondents to understand. For example, the questioner could ask the respondents how much they would pay to have weekday noise levels reduced to weekend noise levels. Make sure the questioner describes a realistic way for respondents to pay for the reduction, or many of them will say they are unwilling to pay anything.