Practical Game Design

Making audio optional

Unless your game revolves around audio design, be it spoken lines of dialogue (for example, Thomas Was Alone, Stanley's Parable), music (Guitar Hero, Rock Band, Audiosurf) or sound cues (for example, footsteps and shots fired in Counter-Strike and Rainbow Six: Siege), you should avoid relying on audio cues. On top of isolating hearing-impaired players, you're also disadvancing people who play with low or muted sound. The probability of the latter is extremely high in the mobile and portable game market.

As for supporting hearing-impaired players, on top of integrating subtitles, you should also consider putting in options to enable closed-captions (textual descriptions of sound effects). For example, door creaks or ...