The ornamental design for an earphone, as shown and described.
1. Earphone
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Left
1.5 : Right
1.6 : Top
1.7 : Bottom
1.8 : Reference
The broken line showing in reproduction 1.3 is for the purpose of illustrating portions of the earphone and forms no part of the claimed design. The solid concentric circle around the broken line circle on the earphone in reproduction 1.3 forms a boundary to the claimed design and the area within, including the broken lines, does not form part of the claimed design. Reproduction 1.8 is a reference view showing the earphone in a state of use. The broken lines in reproduction 1.8 depict environmental subject matter and form no part of the claimed design.