Question for those who use a Doppler. With my son, the placenta was attached to the posterior wall,…

Question for those who use a Doppler. With my son, the placenta was attached to the posterior wall, but I'm not exactly sure how it felt with the home Doppler; I think I most often found the heartbeat in the middle without issues, while on the sides I felt the pulsation of my own veins or arteries. Now, based on the ultrasound, the placenta is attached to the anterior wall. And right now, in the middle, I can't find the baby's heartbeat; I can only hear it on the right or left, sometimes having to shift the probe toward the center. In the middle, I hear a noise and blood pulsation. Is that the placenta? Who has an anterior wall attachment (who uses a home Doppler? Do you hear it the same way?)?