NGX and ATC sound volume in squawkbox

Though the sound level is maxed in settings, the volume of the ATC sound in squawkbox is often very low relative to the sound of NGX. So I'm having trouble when listening to the ATC, can't understand what he says sometimes. I often push "Q" key to mute the FSX when ATC is calling me, so that i only hear ATC sound. Even i lower the master volume from 50 to 10 through FMC, it is very hard to hear what ATC says. One option is to lower all volume levels through FSX sound settings but for the best experience PMDG advices to set all of them to %50, so i don't want to do that. Does anybody suffer from the same problem?