Abstract: Apparatus for setting or adjusting an aural prosthesis, such as a hearing aid, in order to provide compensatory amplification or attenuation for aurally handicapped persons such that the prosthesis compensates for the specific auditory deficiencies of that person. The apparatus includes a master hearing aid having one or more adjustable gain controls for determining the person's preferred word discrimination levels for a plurality of frequency bands. As the master hearing aid is set at the person's preferred level for each separate band, a reciprocal control coupled to each master control is adjusted at the same time. A hearing aid is then selected having an acuity deficiency correction characteristic generally similar to that determined by the previous test information, and that hearing aid is coupled to the reciprocal gain controls. The hearing aid selected is of a type which may have one or more adjustable filter networks and a maximum power output adjustment or any combination of one or more of these.