Laminar Research released X-Plane 11.50 which is breaking some addons. DreamFoil Creations' Bell 407 was one of them but the team already released a fix.
Have you installed X-Plane 11.50 to give it a try but your DreamFoil Creations Bell 407 is mute?
Don't worry! DreamFoil came to our rescue! The team released a patch that fixes the sound issue with the helicopter in the most recently X-Plane beta. And it seems to be retro-compatible with X-Plane 11.41 as well.
Download the patch here and go enjoy your 407 in its full glory.