I don't know if you would count the alien children in that area, but I have been playing the family where the male had a baby. Astra, and she is quite pretty
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Anyhow, she didn't make any sounds until she aged up to teen, then her voice was the high pitch sound. She was a normal child in all ways despite green skin, pointed ears, hugh black eyes and no hair. The other family members could hear her, but I didn't hear any sounds, so I guess it was my computer, not able to handle her voice.
At teen I could hear her voice, high pitched, she was able to probe, absorb rocks for brain energy and give or take power away from other sims. She also started to sleep less, she needs just a few minutes of sleep, and had gone for three nights without sleep, yet kept the well rested moodlet. I sent her to bed so I have no idea of how long she could have stayed up. I send her to bed after two nights, even though she doesn't seem to need it. She sleeps for about 15 minutes, plus or minus and then is up and ready to go.