This plant is to be located 1600 ft. from a military base hospital, and it is the designer’s responsibility to specify the acoustic requirements of the pack- aged generator. The gas turbine power output shaft, operating at 7200 rpm, drives a gear which in turn drives a generator at 3600 rpm. The Engine Room and the Generator Room are ventilated by 30-hp fans, as seen in the exhaust vents of these two rooms in figure 4–3. The manufacturer pro- vides a housing for the entire unit that is made of l/16-in. -thick sheet steel with a 4-in thick absorb- ent lining on the inside, covered with 22-gauge per- forated sheet steel. Consideration should be given to the following parts of the noise problem: Muffler requirement and design for the air inlet to the en- gine, muffler requirement and design for the en- gine exhaust, noise escape from the walls and roof of the entire package, noise escape from the venti- lation openings of the Engine and Generator Rooms, hearing protection for operators, when necessary, and acceptable noise levels in the Con- trol Room. In this sample problem, only the intake and exhaust muffler requirements are evaluated. Details of the other parts of the total study would follow along the lines of the example given in detail in paragraph 4–2. b. PWL criterion for noise to hospital. It is first required to estimate the total PWL of the power plant that will just produce acceptable sound levels inside the hospital building at a distance of 1600-ft. An indoor criterion of NC–20 for patient rooms is wanted. This low level is selected to help reduce the audibility of the tonal sounds of the plant. The hospital is fitted with sealed-closed windows, with each room receiving some fresh air through small wall vents to the outside (similar to wall type C in the N&V table 6–10). There is a tall growth of me- dium dense woods between the power plant and the hospital. The woods are about 500 ft. deep, and the trees are about 40 ft. high. The top of the exhaust stack of the power plant is about 30 ft. above ground elevation, and the upper windows of the two-floor hospital buildings are about 25 ft. above ground. The approximate insertion loss of the woods is esti- mated with the use of DD Form 2300 (Elevation Profile Between Sound Source and Receiver Posi- tion) and DD Form 2301 (Estimation of Insertion Loss of Vegetation in Outdoor Sound Path). Fig- ures 4–30 and 4–31 are filled-in copies of these two data forms. . dense woods between the power plant and the hospital. The woods are about 500 ft. deep, and the trees are about 40 ft. high. The top of the exhaust stack of the power plant is about 30 ft. above. 4–2. b. PWL criterion for noise to hospital. It is first required to estimate the total PWL of the power plant that will just produce acceptable sound levels inside the hospital building at a distance. the plant. The hospital is fitted with sealed-closed windows, with each room receiving some fresh air through small wall vents to the outside (similar to wall type C in the N&V table 6 10) .