90 to 95 percent of deaf people come from hearing families, and most never learn sign language. Only about 1 percent of deaf people in the US use one. There are 300 distinct sign languages globally, none of them mutually intelligible by default. Lip-reading recovers roughly 30 percent of spoken words. These are not edge cases. They are the baseline facts that most product teams get wrong before a single design decision is made.
Hearing loss is a spectrum measured in decibels, running from slight loss at 16 to 25 dB, where a person misses 10 percent of speech at 3 feet, to profound loss above 91 dB, where only a car horn at 110 dB registers at all. At 50 dB, a person misses 80 percent of a normal conversation. Deafness also has three distinct identity categories with real consequences for how you communicate: capital-D Deaf, lowercase deaf, and hard of hearing. Using the wrong one is not just imprecise, it signals you have not done the work.
The full article by Vitaly Friedman on Smashing Magazine goes deeper into practical UX guidelines, including how to handle captions, visual alerts, and inclusive content design. The section on respectful communication protocols and the breakdown of sign language as a 4D spatial system with its own grammar are worth reading in full, especially if your team is making assumptions about text as a universal fallback for deaf users.
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