How to reduce voice volume?

My 18-year-old daughter can't seem to regulate her voice volume, and her natural tendency is to approach yelling volume without constant reminders.  Her health and developmental issues that seem most closely related include Aspergers, speech impairment associated with facial paralysis and a very small jaw, mild to moderate hearing impairment, and a broader diagnosis of Moebius syndrome.  She gets speech therapy through school and we constantly remind her when her volume gets too high, but nothing seems to work.  It's a barrier to her already limited social interactions, and it hurts our ears.  Any ideas?

[Rachel Thompson, Ph.D., BCBA]

The purpose of your daughter's communication is to get your attenton or to get something else that she wants. If the whole family requires appropriate voice volume for either of those things, I would expect that her volume will decrease very quickly. Tell her once that you will only respond if she uses her "inside voice" (or whatever phrase you typically use). Then quickly respond when she follows this rule, but ignore yelling. At first, you can expect that she will yell louder and perhaps protest in other ways. But, as soon as she learns that won't work, I would expect her to adjust her volume.