Abstract: In-ear headphones comprise a headphone shell, wherein a sound making unit and a control circuit are installed in the headphone shell, a first cavity, a second cavity and a third cavity are accommodated in the headphone shell, a first microphone is transversely installed in the first cavity, a second microphone is vertically installed in the third cavity, and the first microphone and the second microphone are connected to the control circuit through a sound signal transmission line; the sound making unit is transversely installed in the second cavity, the sound making side of the sound making unit upwardly faces toward the sound making opening of the third cavity, and the second microphone is located above the sound making unit.

Abstract: A jack for preventing a headphone from inputting double audio sources includes: an audio jack set including a left audio jack and a right audio jack, which are respectively provided on bottoms of a left earpiece and a right earpiece of a headphone and for connecting an audio connector. The left audio jack includes a first common grounding contact, a first conductive terminal and a second conductive terminal. The right audio jack includes a second common grounding contact, a third conductive terminal and a fourth conductive terminal. Two audio jacks are provided for users to select. Simple mechanical switches are additionally provided, which only allow one inputted audio signal to input to a left earpiece and a right earpiece of the headphone for playing audio, and thus are capable of preventing users from inputting two different audio sources to the headphone simultaneously.