Hi @akimayqueiroz
Listen closely and check if you hear if sound is heard in both the left and right side headphone speakers. Listen to only one side and then the other side so as to be sure if they're both working or only one side is working
It may be that one or the other is not working and that is why you're hearing only the instruments and not the voices i.e. mono audio and not stereo audio.
Depending on which side it is will depend on what and where the problem is.