Your hearing aid is composed of a microphone, a sound processor and a speaker. While the hearing aids has limits on what is placed in your ear canal through the design or limitations of the speaker in your ear, and thus will not affect the speaker or sound processor; there is no limit on what the microphone will try to transduce or turn from sound in the environment into electricity to send to the processor. A microphone is a mechanical part made up of a thin magnetically charged material that moves in response to sound. If there is a loud sound, there is a large movement. A really loud sound CAN and HAS caused damage to the microphone. I have had patients who have had their hearing aids break from being exposed to sirens and airplanes flying closely overhead.
With ultrasound, it depends on the frequency and the loudness. I would never say never, but the microphone is tuned to audible speech, and thus I would say that it would have to be even more energy than what I described above.
Hope this helps.
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