[rotrex]

I have tried different nozzles, there is hardly any difference.
The noise is most likely fluid hitting the compressor housing wall at high speed.
My intake uses a closed airbox. You don't hear the compressor with the roof off.
The airbox dampens the turbine's sound pretty well. This leads me to concluding it is the turbine housing as sound cannot not transmit through the intake air.
When I used a open cone filter at the beginning, it sound like a jet fighter or a XXL industrial vacuum cleaner on steroids in the engine bay. It is pretty loud.