Sound is a compression wave in the air. At the simplest scale the air pushes toward you and then away from you. When you have more than one sound source, the sound waves can interact. If one source causes the air to move toward you and the other causes the air to move away from you, the two sounds cancel out and you hear nothing.
Most sounds are complex, and to cancel them you need some sophisticated circuit as a source, like noise cancelling headphones.
Latest Answers