... I'll just go ahead and assume based on your only other post that you've only downloaded Visual Novels made with Ren'Py engine and it's not some locale issue or something else with your system.
See if anything there helps:
https://f95zone.to/threads/sounds-not-working-in-some-renpy-games.2904/
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some show sound levels in the settings for voice and music etc but in all cases the voices don't play
In case of Ren'Py, if a game has voiced characters (which
isn't common in Western, non-Japanese Visual Novels), it should have a separate audio slider in the options for that. Other sliders are only for music tracks and sound effects (and do not necessarily mean the developer added any to the game, either), so games with only those don't have voices in the first place.