When did headphones become common?

As a result of the Walkman effect beginning in the 1980s, headphones started to be used in public places such as sidewalks, grocery stores, and public transit.

Did headphones exist in the 70s?

By the 1970s, headphones had established themselves beyond the realm of work as a way to enjoy music – even in hi-fi sound quality — without disturbing others. … The ear pieces were covered with foam and the sound was not exactly hi-fi, but pretty good.