11 Determine whether the full-capacity tunnel or the half-capacity tunnel should be constructed now. Solve the problem by B/C ratio analysis using a 5% interest rate and a 50-year analysis period.There will be no tunnel lining repair at the end of the 50 years.

Consider the following typical noise levels in decibels (dBA):

140 – threshold of pain 130 –

120 – four-engine jet aircraft at 500 ft unmuffled motorcycle 110 –

100 – rock and roll band subway train at 20 ft 90 –

heavy traffic at 25 to 50 ft 80 –

vacuum cleaner 70 – dishwasher 60 – conversational speech at 3 ft 50 – business office 40 – home

a. Assume that you are responsible for designing a machine shop. How would you determine an acceptable level of noise? What costs and risks should you weigh?

b. What would your answer be for the design of a commercial aircraft?