It’s not every day that I get to test an a11y app, that later became into a product. Google recently launched two apps to make the life of people who are deaf or hard of hearing easier: Live Transcribe and Sound Amplifier.
Official announcement:
https://www.blog.google/outreach-initiatives/accessibility/making-audio-more-accessible-two-new-apps/
I am a fan of Live Transcribe in particular. The apps listens to your call or the surroundings of your phone and generates captions automatically. It works with even several languages.
I had the honor of testing it early and I am happy with the result. I hope it does a good job for you too.