Original sentence: As of 2006, this decrease in singing ability has been variously attributed to his smoking habit, age, prolonged overuse, and/or singing at the top of his vocal range.His voice is known for its 'grinding', 'razor sharp' sound, though over time his range has reduced
Edited sentence: Brian Johnson can no longer sing as he once did, however that's not to say his voice is bad per-se, it's just not as good as it once was.This decrease in singing ability is most likely attributed to his avid smoking habits