US Patent 8045726 Noise-cancelling headphone

A noise-cancelling headphone includes a cancel signal generator that receives ambient noise via an electro-acoustic transducer and generates and outputs a cancel signal eliminating the noise and a speaker unit that outputs an audio signal and a cancel signal, and connects the cancel signal generator to a first terminal of two input terminals of the speaker unit and connects a sound source of an audio signal to a second terminal thereof, whereby obtaining the noise-cancelling headphone with which one can enjoy music with high quality without the change in the sound quality and volume between when a noise-cancelling function is activated and when deactivated.