A headphone set can enable the substantially simultaneous output of two or more audio sources to a user. The audio from the multiple sources may be mixed so that a listener can hear and understand audio received from multiple audio sources. Thus, in certain embodiments, a user can consume media and also engage in conversation with other users or listen to ambient sounds, such as a telephone ringing or an alarm. Further, a mobile device, such as a mobile phone, can mix audio from multiple sources enabling a user to consume audio from the device while also listening to ambient sound or audio received from a source other than the device, using currently-available headphones.