Yes, police officers can generally hear a motorcycle with a stock exhaust, even if it doesn't have a baffle or muffler. While the noise level may vary depending on the specific motorcycle model, most stock exhaust systems are designed to meet noise regulations and emit a noticeable sound that allows people, including law enforcement, to be aware of the presence of the motorcycle. The sound produced by the engine and exhaust system can still be audible enough for police officers to identify and potentially enforce noise-related regulations, depending on the circumstances. It's important to be mindful of local laws and regulations regarding motorcycle noise to avoid potential legal issues.