This is the place to post questions and discussions on usage and style. The members of the Wordwizard Clubhouse will also often be able to help you to formulate that difficult letter.
Sometimes more detail is helpful, especially if the person you're talking with will be talking with the partially deaf person later. My husband & sister are both totally deaf in one ear; can't hear you if you're on one side, but can hear just fine on the other. Unfortunately, for them it's opposite ears. Standing or sitting to the left of my husband is a habit 35 years in the making. My sister's deafness is more recent, so I often have to be reminded to talk to the other ear.