3 Ways!
Well, assuming you've got the master ATC volume cranked up to full in the Sounds Settings menu of FS9 and you still can't hear it in this aircraft, then the easiest way would be to drop the master volume of the Engine Sounds in the 'Sound Settings' menu of FS9.
Another way, if you have a wave file editor that is, is to open all the internal engine sounds up with it, & reduce the volume levels of them all and save them, or at least the ones that are giving you trouble. If you do this, make sure you make copies first, and keep the masters safe.
If you can't do that, or don't want to do the first method, then you could open up the aircrafts Sound.cfg (in the 'Sounds' folder and look for the vparams line ), identify those sounds who's volume you want to change and lower the volume envelopes of all the sounds, or again just those that are causing the problems with ATC. However, you are probably better using an editor like FS Sound Studio which lets you do this via a GUI with instant feedback of the changes, rather than doing it by hand and guessing!
Cheers
Paul
