A notch filter is a type of electronic filter designed to remove a specific frequency from a signal while allowing other frequencies to pass through. It is commonly used in audio processing to eliminate unwanted noise or interference, such as the hum from electrical equipment. By targeting a narrow band of frequencies, notch filters help improve the overall quality of sound. These filters are often used in various applications, including telecommunications and medical devices. For instance, in medical imaging, notch filters can help reduce interference from power line frequencies, ensuring clearer signals for better diagnosis.