Knowledge: The first loudspeaker was invented by Alexander Graham bell in 1876. However, the first headphones were founded by Nathaniel Baldwin and used in World War II.

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
Can you tell me when headphones were invented?

Response: The first headphones were developed by Nathaniel Baldwin and used in World War II.