Speed of sound gas + liquid

for a pipe with a two phase mixture of hydrocarbons + water at high pressure (> 70 Bar) to solve a critical flow should I calculate the speed of sound for gas + liquid ? (probably there are three, liquid-liquid-vapor phases)
How can I proceed ?

for a two-phase flow you can apply the HEM (Homogeneous Equilibrium Model),
HEM allows to calculate the speed of sound in two phases (vapor+liquid) flows,
with hydrocarbons + water you need to solve a three phases (vapor-liquid-liquid) equilibria,

I utilize Prode Properties which includes methods for calculating the speed of sound for gas, liquid and gas+liquid

ss = StrMSS(stream)
given a stream returns the speed of sound for gas, liquid and gas + liquid (for gas + liquid with HEM model)

ss = EStrMSS(stream,t,p)
given the stream pressure and temperature solves a isothermal flash at p,t and returns the speed of sound for gas, liquid and gas + liquid (for gas + liquid with HEM model)

these methods are available in Microsoft Excel as Macros,
for calculating the speed of sound for a gas + hydrocarbons + water mixture follow these steps

1) define the stream composition, models and BIPs (since there is water which can originate a three phase equilibria set multiphase vapor-liquid-liquid as option for phase equilibria)

2) in a cell put the macro =EStrMSS(1,$B1,$B2) which instructs Excel to calculate the speed of sound at specified temperature and pressure (see attached image SpeedofSoundinExcel.jpg)

3) modify the temperature and pressure and Excel will recalculate automatically the speed of sound for gas, liquid or gas + liquid phase