The ornamental design for a hearingaid, as shown and described.
1. Hearing aid
1.1 : Perspective
1.2 : Top
1.3 : Bottom
1.4 : Right
1.5 : Left
1.6 : Front
1.7 : Back
Fig. 1.1 is a top, front, left side perspective view thereof, fig. 1.2 is a top view thereof, fig. 1.3 is a bottom view thereof, fig. 1.4 is a right side view thereof, fig. 1.5 is a left side view thereof, fig. 1.6 is a front side view thereof, fig. 1.7 is a back side view thereof.
The broken lines shown in the figures depict portions of the hearing aid that form no part of the claimed design.