Noise distribution law of air-conditioning ducts for metro vehicles

The passenger comforts are directly affected by the air supply uniformity and noise of air-conditioning duct inside the metro vehicle. In order to solve the integrated design problem of air supply uniformity and noise control of air-conditioning ducts, a theoretical model is established to analyze the air supply uniformity, noise attenuation, and airflow regeneration noise of the air-conditioning duct. The distribution law of the sound pressure level along the longitudinal air outlet was calculated, and the calculated results were compared with test ones. For a typical air supply duct with a constant cross section: (1) In order to ensure air supply uniformity at the outlet of the static pressure chamber, the area of the side air hole should be gradually increased in an exponential form along the direction of the main flow, and cannot be designed in the equal area form. (2) The airflow speed of each side hole decreased in sequence along the air duct length. In order to ensure the uniformity air supply of each side hole, the area of each side hole must be gradually increased. (3) The noise in the air conditioner duct was mainly concentrated at the front end of the air duct, and the noise at the subsequent air outlet can fully meet the current requirements of subway vehicles for indoor noise. Therefore, the front end of the air duct is the most important area for noise control.