ABSTRACT
Suppose that an initial expenditure of $100,000 per annum in muffling the noise on all the aircraft to that destination reduces the cost of the noise to people living within the relevant area by $180,000, the original curve EE1 has to be lowered, say to E′E′1. Each of the OB1 flights, that is, now inflicts less noise on the community, the reduction in cost for any one flight being measured by the vertical distance at that point between the original EE1 curve and the E′E′1 curve. The area or the strip between the two curves, EE′E′E′1 is, therefore, equal to the benefit of $180,000 (or reduced cost) from the resulting reduction in noise. A further expenditure of $100,000 on muffling aircraft noise has the effect of
reducing the cost of noise by, say an additional $140,000, lowering the cost curve to E′′E′′1 . Clearly, we can continue in this way until the value to people of a further reduction in aircraft noise is no greater than the expenditure required to produce that reduction. If we assume that the curve E′′E′′1 is as far as we can go in increasing the net
social gain by the method of noise muffling, it will be observed that there are still a number of flights, measured as the number from Q′′ to B1, that will continue to create noise whose cost is above the excess benefit from the flights. Therefore, by eliminatingQ′′B1 flights per annum, we can secure a further net social gain which can be measured as equal to the area of the triangle E′′1CB1. It may be concluded that the more effective is this second method of muf-
fling aircraft noise, the greater will be the reduction of the cost-of-noise curve EE1. Consequently, the fewer will be the number of flights that have to be eliminated in order to reach an optimal reduction in aircraft noise when using both methods I and II.
