What!! There are like 3000'ish extracted files there, and I do not know the game, so I cannot know which hidden message you refer to. Based on your initial guessing in your OP, those files you uploaded should (my guess! as I do not know the game) contain the audio you search, so I devised the extraction process and posted here, with the hope that yoo would afterwards search for the file yourself. If you did extraction and got the extracted files, then my contribution to this thread is done. I listened to the audio in the video. It sounds like 2 channels to me, i.e. probably mixed tracks, the bgm & some voice sfx. As it is mixed, there is also the likeliness that this specific SFX is on another file (there have been cases where a lone audio was in another, non-resource file - even in a dll library for some PC game!!!). Try with sample_rate = 8000 first in the TXTH, in order to find your required file. Patience, my friend.
edit: Yes! it very likely is a voice sample, maybe in your OP's files, maybe in another file.