> questions about how the hearing impaired use video chat

I am not deaf or hard of hearing, but have a teenage daughter who is old enough to articulate some of these things. She doesn't sign (used to, and there's reasons beyond "didn't use it" that she doesn't) and what she's told us is:

(1) Video calls are better than audio-only, but just barely. If you watch her with a group of friends, she's not always looking at the person who she's directly communicating with. She uses her vision to keep up with fast moving, multi-party conversation and to fill in missing sounds. She hears sounds well into mid-range tones. Deeper and high-pitched tones are not heard at all, but she can feel the deep tones[0]. Through lousy laptop/phone speakers, it's all mid-to-high tones and -- I get the impression that people sound much different to her over speakers than they do in person, but I have no way to confirm that.

(2) Without closed captioning, she misses a lot. She doesn't read the captioning word-for-word but uses it like lip-reading -- to fill in gaps for sounds she can't hear. This happens more frequently than to me (I have very mild hearing loss; a little worse than a normal person at my age) -- sounds might be heard, but a competing sound ruins the "signal" (signal/noise ratio) more for her than it does for me. Worse, because video conferencing software likes to focus on the speaker, and the latency involved in switching to the speaking is very long, it can make the calls even more confusing.

The second point can't be stressed enough. My daughter is not completely deaf. She doesn't "lip read" in the way you see on TV[1] -- she can hear enough that she does it unconsciously. My daughter (and Mom and Dad) had no idea how much she relied on lip reading and closed captioning (it's on by default on all of our TVs so we don't even notice it). When Zoom meetings and mandatory mask wearing came along, it took very little time for us to notice she was struggling way more than the other three kids. It took about a month before we figured out why.

In her schooling situation right now (online-only public school -- one not setup specifically for COVID), video/audio conferences are somewhat minimal. Teams works good enough for her, and she's adjusted by pre-reading the materials -- basically learning whatever it is that's about to be taught to the other kids -- because it's easier than trying to learn it from the live lesson. If she didn't have to attend these sessions, we wouldn't make her. Thankfully, video/audio/live lessons are very minimal in the program her and my son are enrolled in.

[0] Something I learned (my daughter is more accurately my step-daughter, so I met her when she was about 4 years old) -- she had a terrible fear of fireworks until she was about eleven. We found out this is a really common thing with people who are hard of hearing. After a lot of questioning, it would seem that she feels the "boom" of the explosion but the corresponding sound is very quiet or just missing entirely. Combined with the difference between the sight of the explosion and the time it takes for the sound to reach your body, it resulted in her being startled, constantly.

[1] ala Seinfeld - You couldn't have her spy on someone's conversation without hearing their voice -- while she's better at it than I am, she's still about a time zone away from the actual words that were said.