Sonic velocity and choked flow

[ssk]

I have got a confusion w.r.t to the sonic velocity and choked flow equations given in the literature. Using choked flow equations (mass flow) given in safety literature and divide that mass flow with the area of opening and density of the gas, we should get the velocity of the gas which should be near about the sonic velocity. But what I am getting is a velocity which is well below the sonic velocity (which can be found out using the relation sqrt(gc*k*R*T/Mol wt of gas). What may be the reason?
Regards
ssk

[Nephilim]

Difficult to say, which correlations did you use?