Adaptive noise cancelling

Adaptive noise cancelling is a signal processing technique for suppressing interference corrupting a received signal where the interference is known and is accessible but unavoidable and where the target signal and the interference are unrelated. Examples of such situations include: a microphone attempting to receive speech near machinery or other noise sources in the environment, such as an aircraft cockpit a naval ship towing a sonar array where the ship's own noise masks a much weaker detected target signal obtaining a fetal electrocardiogram (ECG) where the presence of the mother's stronger ECG represents an unavoidable interference.

Source: Wikipedia — Adaptive noise cancelling (CC BY-SA 4.0)