The ornamental design for an earphone, as shown and described.
FIG. 1 is a perspective view of a first embodiment of an earphone showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines in the drawings depict portions of the earphone that form no part of the claimed design. Dot-dash broken lines define the boundaries of the claimed design and form no part of the claimed design.