Subscale experiments showed that, relative to the mixed-flow exhaust, the coaxial separate-flow exhaust with vanes reduces the peak overall sound pressure level by 8 dB and the effective perceived noise level
by 7 dB and the noise-equivalent specific thrust on take off is reduced from 490 to 390 m/s.
Caption: FIGURE 4: Preliminary sample survey flow chart to detect the perceived noise level
Referring to Weighted Equivalent Continuous Perceived Noise Level
(WECPNL), an international environmental index for airplane noise, Watanabe said in his ruling, ''The residents in the area with over 75 WECPNL suffer damage beyond tolerable limits.''
According to this scale -- the weighted equivalent continuous perceived noise level
-- noise in residential areas should not exceed 70.
The tests establish certified aircraft Effective Perceived Noise Levels
(EPNLs) for each of the flight conditions: approach, flyover and sideline.
The company says the system and a single layer of 1/2-inch drywall board can reduce perceived noise levels
by up to 65 percent compared to an uninsulated wall.