Mapping of hearing aid channels (HACs) between medium and high technology level (TL) of manufacturer A, B, and C. The row indicates which HAC of the medium TL has the largest overlap with one or multiple HACs of the high TL. If one or multiple HACs of the higher TL could be clearly mapped to one HAC of the medium TL, they are marked with the same color as the HAC of the medium technology level. If no mapping between both TLs could be found, the cell of the HAC of the high TL is left white. The number of HACs available in the fitting software within the considered frequency range are listed in Table 1.