I noticed that several manufacturers sell open fit hearing aids with an ear hook. The aid is identical to the aid without the ear hook but the fitting range may be 10 DB greater than the one without an ear hook. What is the reason that an aid with an ear hook may be more powerful than one without an ear hook?
As an example, the Sonic Innovations Ion 200 with an ear hook has a fitting range to 90 DB where as the one without the ear hook has a fitting range to 80 DB. However, the Sonic Innovations Ion has a fitting range of up to 80 DB with or without an ear hook.