What is a Hum (Ground Loop)?

A ground loop hum is a type of unwanted noise that occurs when multiple audio devices are connected to different electrical grounds, creating a loop in the grounding system. This loop can allow electrical interference to enter the audio signal.

Ground loop hum typically produces a low-frequency buzzing or humming sound, often around 50 Hz or 60 Hz, depending on the electrical power standard in a region. The noise may also include higher-frequency harmonics that make the hum more noticeable.

Ground loop hum often appears when multiple pieces of equipment such as audio interfaces, mixers, amplifiers, computers, and powered speakers are connected together through both audio cables and power connections. Engineers usually resolve the issue by improving grounding, using balanced cables, isolation transformers, or ground loop isolators to break the unwanted electrical path.