This is the 1070th most frequent Polish word.
głosu
The Polish word "głosu" means "voice" or "vote" (genitive singular form of "głos").
Here, 'głosu' means 'voice' in a genitive-case form to indicate possession or absence.
Nie słyszałem głosu w sali.
I didn’t hear a voice in the room.
In this case, 'głosu' is used metaphorically to mean 'voice of conscience,' expressing internal guidance.
Powinienem posłuchać głosu sumienia.
I should listen to the voice of conscience.
'Głos' refers to a 'vote' in this context, and 'głosu' is in the genitive case to reflect an action performed with it.