Knowledge: FM radios started to gain popularity among the people in the 50s and 60s as a viable alternative to AM Radio. However, headphones became ubiqitious in the late 1970s and 1980s

Conversation:
Do you use headphones often?
I can't use such things as I am a bot. But I know that they area bout. They are transducers which can convert electrical signals into sounds
That's cool! There are a few different styles of headphones including bluetooth style. Are you familiar with those?
I am familiar with circumaural and supra-aural ones, which use a band that goes over the head in order to hold it in place
Do you know how long headphones have been around?
Yes! They were invented in the 19th century for telephone operators.
That's right! I didn't realize how they were used for early telephone communications.
Yeah that was to keep them with free hands
Do you know when they started to become commercially popular for people?

Response: In the late 1970s and 1980s, headphones became widespread.