A: Using the Doppler machine, which looks like a small microphone, we can usually hear a baby's heartbeat by 12 weeks into pregnancy. The two different sounds that you hear on the Doppler most likely are your baby's heartbeat and your heartbeat, which is about half as fast as your baby's.The sounds you hear will vary depending on where the doctor places the Doppler monitor. If it's directly over the baby's heart, you'll hear a cloppity-clop, like horses trotting. If the monitor is near your umbilical cord, it'll sound more like a swoosh-swoosh. Both are normal, and signs that your baby is healthy and developing right on track!