in the Cessna 172 it,s easy, the audio mixer panel is above the GPS units
just disable the one that says MKR (circled) and the markers sounds won’t be audible, you’ll just see the O M and I lights when flying over the markers
look for something similar in other planes, for the 747 I don’t know, seems like the buttons that control sound in the center console between the seats are inoperative, so I’m not sure how you are supposed to select what you want to hear… maybe someone else here knows