Classic TV - Tales of Tomorrow - "The Great Silence" (1953)

A mysterious phenomenon that causes people to lose the use of their vocal cords appears in a remote corner of the northwestern United States and begins spreading. The government blames the event on freak fallout effects from H-Bomb testing, but an illiterate mountain man (Burgess Meredith) discovers the real source of the affliction.
https://www.imdb.com/title/tt0717067/plotsummary?ref_=tt_ov_pl

This video is in the Public Domain.