The ornamental design for a microphone, as shown and described.
FIG. 1 is a perspective view of a microphone, showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a perspective view of the microphone shown in an environment of use.
The broken line showing of the stand in FIG. 8 depicts environment and forms no part of the claimed design. All other broken lines depict portions of the microphone that form no part of the claimed design.