It might surprise you to learn that it is completely legal to listen to official police scanner radio transmissions in the United States. There is even a hobbyist community dedicated to exactly that, which is full of people who find it interesting to hear what the police are up to as they go about responding to crimes and other dispatches. Some states do have a couple of limitations, such as listening while driving or while committing a crime. But as long as you’re just listening at home, it’s legal in every state. If you want to do that yourself, YouTuber Kevin Darrah has a guide on how to use a Raspberry Pi to build an inexpensive police scanner.