When does baby react to outside voices?

Lauren • Our little miracle Caroline arrived 1/28/15! Thanks glow!
Hi all,
​Anyone know when baby starts to react to sounds and voices? My hubby talks to my belly every night, but the baby doesn't really react. Her kicks are random, but I know it's still sort of early since I'm only 17 weeks and 5 days. I googled but everything says something different!  Thanks!