Coil whine is a high-pitched buzz or whine produced by some electronic devices, usually when current through an inductor makes the component vibrate. The sound is often more noticeable under changing power demand, such as when a GPU, power supply, or charger is working hard. It is not a software error by itself, but it can be a useful physical clue about what a device is doing.
In cyber security, coil whine matters because attackers and defenders both care about unusual hardware behavior. Malware that pushes a system into sustained high load, such as cryptomining, may make the noise more noticeable. Security teams may also treat unexpected buzzing as one more indicator during device inspection, especially when checking for abnormal workloads, power issues, or tampering. It is a reminder that some security signals are audible, not just digital.