My sister's kid is 5 years old and I watch him while she's at work. I'm autistic and have auditory processing problems so I can't hear him when he mumbles softly which is all he ever does when he speaks. I get enough of this at my job with having to constantly ask grown adults to speak up (they never do) so i don't want him to grow up to not speak clearly. He mumbles with his mouth barely open and blocks his mouth with his face or knees or looks away. He goes back and forth between doing it in a cutesy way and doing it while glaring at me. Both ways irritate me as I'd rather he ask me directly in a nice way. I know he's capable of talking louder because he shouts at his video game while others are trying to sleep, it's just while speaking that he refuses to be loud. I've spoken to him about it and explained that I can't hear him if he doesn't speak up and open his mouth when speaking but I get nowhere with it. He just tells me that I "don't get it" because this is his "cute voice". (I don't respond to kids trying to be cute on purpose because in my experience with my younger siblings growing up, kids who acted cute got away with things that I didn't so I'd rather be spoken to in a direct way instead of trying to elicit a response.) I'm never mean when asking him to speak up but I have to keep insisting on it because I can't hear what he's asking me to do and half the time he isn't asking he's just telling me to get something for him in a very sullen, angry way. I keep modeling how to ask the question in a nice way but he covers his ears and ignores me. Does anyone have any advice? I fear this behavior will turn into a bad habit as he gets older (my younger brother never grew out of that stage and is a very volatile and manipulative adult.)
encourage/reward good behavior, ignore bad behavior
Children learn incredibly quickly and learn a lot more than we give them credit for. The main issue is that they often don't learn what we want them to learn in the moment.
If that child keeps trying to ask you for favors in a cutesy way it's most likely because that has worked for him before. If that didn't work they became angry because they didn't got what they wanted and most likely that has worked too before.
There is a silver lining to this tho. In that they also quickly learn what does and doesn't work with different people. So you should be able to teach them to speak up to you and you already said how yourself:
I don't respond to kids trying to be cute on purpose
Just take this a bit further. Any time the child speaks too softly you just pretend he didn't speak at all. If he uses the angry soft voice you do the same. Just keep playing (/doing what you were doing) as if he had not said anything.
If any time he tries to get his way by being cutesy with you has absolutely no effect but the very first time he speaks up he instantly gets a response he'll probably quickly transition into speaking up more often to you.
You should "reward" speaking up tho to reinforce that being the effect you want. So any time he does speak up you start by acknowledging what he said.
child speaking up: "Bring me that toy!" you: "Oh you want me to bring you that toy?"
tho I should also add here that you don't necessarily have to actualy give him what he is asking for. Just giving attention is a reward in itself while at the same time you want to teach him that just giving commands to people also isn't the way to get what he wants. So a possible continuation of that dialog could be:
you stretching your arms towards the toy saying in a playful way: "But I can't reach it either! Oh noes! what should we do now?"
If he doesn't try the wanted way by himself you could also try to give him hints on how he could get what he wants (in this case getting a response from you). For example, you could pretend that there is a third person in the room and you inform that third person:
"If only <child> would speak up a bit, at least then I would be able to hear it when he is trying to talk to me." *fake sad face* "It would be so much more fun if only he talked to me some more ...
Or if they get really frustrated because you ignore them too much you can even directly tell him "If you speak up when talking to me, I will respond to you. I have bad ears so I can't understand you when you are too quiet.".
Acknowledging the feelings of a child helps a lot.
I do like to add one important addendum to the ignoring bad behavior: This obviously only goes for things that do not endanger anyone. If a child hits you for example you should immediatly make it clear that they are never allowed to do that, preferably even scaring them a little bit (but never hurting them):
grabbing him by the arm and with a stern voice: "We never hit anyone! Don't do that again." look him in the eyes for a few seconds. Then relax your posture and start talking to him normally again.
This type of stern warnings should only be used sporadicaly when they are really necessary. Like when the child hurts someone (you) or is about to break something on purpose for example.
As long as you are consistent in rewarding (mostly with attention) good behavior you should be seeing results rather quickly. I'd say being autistic is actually helpful in staying consistent in that regard.