A headphone includes an electroacoustic transducer and a support structure for suspending the transducer adjacent to a user's ear when worn by the user such that the headphone is acoustically open. A first microphone is coupled to one or more of the transducer and the support structure such that the first microphone is located in a substantially broadband acoustic null of the transducer. A processor is coupled to the headphone. The microphone receives sound pressure waves and outputs a related electronic signal to the processor. The processor uses the electronic signal to operate the transducer to reduce targeted sound pressure waves at the user's ear.