POWER PLANT ACOUSTICS Episode 9 potx

Item 13 shows an indoor noise excess of 3 to 6 dB in the 125- to 1000-HZ octave bands. This would be rated as “marginal”. If the NC–25 criterion is a justified choice, these noise excesses should not be permitted. A number of other factors could influ- ence the decision. If the housing is exposed to other uncontrollable excess noise (such as nearby highway activity or base aircraft activity), power plant noise might not appear so noticeable. How- ever, if the base is located in a very quiet suburban or rural area, with very little other noise, the pow- er plant noise will be very noticeable. If the base is located in a very hot or very cold region, year- round, and the windows are kept closed most of the time, and if inside sources, such as air conditioners or central heating and cooling systems, are in near- ly continuous use, external noise sources will not be as noisy when heard indoors. These various con- ditions could be used to support or justify adjust- ments to the NC criterion. In the present problem, it is assumed that such factors have already been considered, and the NC–25 selection is a valid choice. (c) A CNR analysis should be carried out as a means of checking or confirming the expected re- action of the housed personnel to the power plant noise. The N&V manual (para. 3–3c) summarizes the procedure. Figure 4–24 shows the CNR grid upon which the outdoor power plant SPLs are plotted (taken from Item 8 of fig. 4–23). A noise level rank of “e” is obtained. 4-35 . the housed personnel to the power plant noise. The N&V manual (para. 3–3c) summarizes the procedure. Figure 4–24 shows the CNR grid upon which the outdoor power plant SPLs are plotted (taken. the power plant. This would reduce indoor SPLs but would not change the outdoor SPLs. If possible, other large buildings on the base could be used to shield the housing area from the power plant. . control the noise. a. Description of power plant. In this example, a 15-MW plant is supplied by the manufacturer in a packaged form as shown in figure 4– 29.