what observations have you seen in this interaction?

Years ago, I drove a school bus for disabled children, one of whom happened to be hearing impaired. I learned some very basic signs from the child's mother. My interactions with her (the child) were largely limited to smiling and to those few signs.

Unfortunately, the hearing person begins to speak louder with more enunciation than normal...there will be a great deal more body language, usually on the part of the hearing person..and both will usually resort to written words...if the hearing person does not speak AMSLAN and the deaf person does not read lips...

One (usually the hearing person) will make a "writing" gesture in the air, and the deaf person will respond with a nod and they will begin their written conversation...

Both make accommodation to write; with a few experimental learnings on the part of the hearign person but the hearing impaired to get this has to put in a lot of unseen work.

The hearing person would speak slower and exaggerate their lip movements, and even possibly talk louder (like they would to a foreigner, even though this doesn't help). The deaf person would use very obvious hand gestures to get across what they are trying to say.

I used to work with a deaf/mute woman. We communicated fine. She was very good at lip reading and I made sure I enunciated my words (but I didn't SHOUT like a lot of people did when they spoke to her...she's deaf...it was pointless) I also learned to read her lips because she could mouth certain words, and use gestures to help me understand. Sometimes, if she had a lot to say, she would just write it.

In all likelyhood, both individuals make the accommodation by switching to written language.