Experimental Investigation of Dust Influences on the Airplanes Sound Pressure Emission

The sound emission of airplanes has some applications such as localization, classification, and detecting fault. Therefore, investigation of issues, which affects the airplanes sounds, is important. In recent years, pollution of dust in all cities of the Iran shows an increasing trend. In the literature, all variables affecting the sound emission such as temperature, pressure, and relative humidity have been investigated, but there are not any researches about the influence of dust on the atmospheric attenuation coefficient. The experimental tests have been carried out with 3 sensitive microphones, 950m away from the takeoff area of Imam Khomeini international airport for 6 different airplanes, including Airbus 320, 319, 321, Boeing 747, 777, and Embraer 190 at different atmospheric conditions. The air temperature was in the range of 20-40˚C and the relative humidity was in the range of 2-34%. At first, the experimental setup was validated by available data, considering different temperatures and relative humidities. In this research, a new variable, β, has been introduced to detect the dust effect, which is defined as: the difference between the calculated sound pressure level at no dust and the measured sound pressure level while the dust density is 1μgr/m3. Airbus 320 has the minimum dust atmospheric attenuation coefficient value (0.01202db*m3/μgr) and its maximum is related to the Embraer 190 (0.0154db*m3/μgr). Finally, the obtained results show that increasing in dust concentration (PM2.5 and PM10) leads to increase in atmospheric attenuation coefficient between airplane and microphones area, and the measured sound pressure level decreases.