I have set up my 737NG for P3DV4 without a problem, except one. I have worked through the FMC setup for the PMDG aircraft, paying close attention to the sound settings. I have set the sound to come through my headset. I also configured the aircraft through the FMC to read out all heights below 1000 ft until landing. I have set the volume to be above 60 (using the scale of 0- 100). All sounds, except the callouts seem to work correctly. Any suggestions on what I might need to do in order to hear the callouts during landing?