FIG. 1 is a perspective view of a hearing aid showing our new design;

FIG. 2 is a right side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a front elevational view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a left side elevational view thereof.

The broken lines in all drawing views are included for the purpose of illustrating portion of the hearing aid that forms no part of the claimed design.