"Sound of Metal" won Best Film Editing and Best Sound in the 2021 Academy Awards. This video describes some of the sound recording and editing techniques they used to bring us inside the main character's head:
Another thing I liked about "Sound of Metal" is that it was open captioned. That means you couldn't turn the captions off - they were part of the film! I noticed the filmmakers deliberately didn't caption (or subtitle ASL) certain moments that Ruben couldn't understand. I felt his frustration in those moments!