Howsit everyone

Yesterday I was driving my evo 7 around, had to do an emergency stop. After 3 miles from the stop the AYC pump started making an electric buzzing sound similar to that of a very large fuel pump.

I thought turning the car off would possibly stop it, it didnt, even with the car off the noise persisted. I proceeded to try and see if some mixed driving would stop the noise which didnt help. I then gave it another emergency stop and the noise went away.

Has anyone else experienced this? Or could shed some light as to what may have caused this?

Much appreciated