17 years ago, I worked for a hearing aid manufacturer. The common terms in use there were BTE and ITE, for "behind the ear" and "in the ear." Frankly, I thought the initialisms were poorly conceived. ITE is three syllables, same as "in the ear," and less meaningful for the uninitiated. BTE only saves you one syllable, again at the cost of meaningfulness. But either which way, your terminology is both understandable and correct.
Off-topic: While I was there, they asked employees to submit ideas for a new hearing aid marketing slogan, with the incentive of a free vacation to Vegas going to the person who submitted the one they used. For some reason, I did not win the vacation with my suggestion: "Stick It In Your Ear!"
It would be pretty interesting to see people assume that a ten-year-old suffered from senility because he was wearing a hearing aid. By definition, it only applies to the old.
Off-topic: While I was there, they asked employees to submit ideas for a new hearing aid marketing slogan, with the incentive of a free vacation to Vegas going to the person who submitted the one they used. For some reason, I did not win the vacation with my suggestion: "Stick It In Your Ear!"