How much noise does flow separation cause?
Flow separation makes a lot of noise. Usually, it is masked by engine noise and/or damped by insulation. Any pilot of a light plane may climb to a safe altitude and then idle the engine, start a glide, and then slowly pull the stick until the wings start to stall. He will hear a lot of noise, and feel a strong vibration, too... The cause is the turbulence associated with the flow separation.