Y’all can tell me I’m stupid it’s okay🤣

So I decided to try out my Doppler to make sure it works before selling it, and just for reference I am NOT pregnant. But while testing out my Doppler I found what seems to be the “placenta whooshing” sounds. I checked to make sure it wasn’t my heartbeat by measuring my own heart beat and then the “whoosing” sounds and they were completely different… so what could I be hearing?