The fetus hears lots of things! They don’t start to gain sound until about 18 weeks around 24 weeks they become super sensitive to different sounds 25-26 weeks they start responded to the sound they are hearing such as them starting to kick when they hear their moms voice. A fetus can hear music that’s why some moms but headphones on their stomp so the baby can hear music. Also, that’s why some fathers speak to the stomach so the baby knows your voice when it comes out. I think the fetus/baby can hear you, music, someone’s voice, practically anything. BUT this isn’t absolutely valid some baby’s don’t necessarily hear anything it honestly depends