Tuesday, 23 July 2019

acoustics - Air oscillation at open window of a moving car


When driving a car with an open window one can hear (and feel) oscillations of air at the threshold of the open window. I used to think the open window and the car interior were forming a Helmholtz oscillator, but then noticed that the frequency of the vibration doesn't change when I change scroll the window up or down, from wide open to 3/4 closed. The amplitude of vibration changes, but the frequency change I don't notice. Thus the two-part question: what causes air to vibrate in the open window? And why doesn't the frequency change when I open the window further?




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