Missing linearised Navier-Stocks module in aeroacoustics.

I reinstall the COMSOL 4.4 (with update 1), and can not find the linearised NS module in the aeroacoustics any more. I can also find the user guide of this module in the help file. (See attachment).

I built some model based on the linearised NS module with 4.4 version (no update 1).

It is too weird. How can I find the missing module?

Thanks !