I'm interested in identifying mass airflow through a choked convergent or conical nozzle. I've found some web info claiming that mass airflow through a nozzle becomes primarily a linear function of the inlet pressure, and doubling the inlet pressure doubles the flowrate. Further research has led me to question the validity of the above statement, that velocity through the nozzle can not exceed the speed of sound in the pressurized medium, compressed air. That the increased density with increased upstream pressure will increase mass air flow, however given a sonic condition occurs at a lower velocity in the compressed air, mass flow doesn't increase in a linear fashion. So, my question is: Which is it?