Fitting multichannel-compression hearing aids.

Multichannel hearing aids have been introduced recently in clinical practice. In this paper, some advantages and disadvantages of multichannel hearing aids are discussed. The advantages include an improved use of compression. However, the number of settings will be larger in multichannel hearing aids and exact knowledge of the goal to be pursued by compression is more necessary than ever. Inexactness of the definitions of these goals may have been a reason for the contradictory results in the studies on multichannel compression. A number of requirements must be fulfilled for a successful application of multichannel compression. One of these is detailed knowledge about the perception of suprathreshold signals. For that reason, an extension of the battery of tests commonly used in rehabilitative audiology is necessary. Another requirement is that the fitting strategy is determined by the purpose of applying compression. The objectives will be different for compression limiting and syllabic compression. A fitting procedure used in clinical practice has to take into account some limitations in the fitting time available. A number of possible fitting tools are discussed. Two strongly different fitting strategies for the same commercially available three-channel compression aid illustrate fundamental differences in fitting philosophy.