The diagrams above are taken from The Speech Chain: The Physics and Biology of Spoken Language, published in 1963 by Bell Labs. The book was part of an educational series about the physical and biological aspects of speech, and includes some fantastic retro diagrams of how speech travels from the speaker to the listener, along with explanations about why speech is such a crucial communication tool:
“Human society relies heavily on the free and easy interchange of ideas among is members and, for one reason or another, man has found speech to be his most convenient form of communication. Through its constant use as a tool essential to daily living, speech has developed into a highly efficient system for the exchange of even our most complex ideas. It is a system particularly suitable for widespread use under the constantly changing and varied conditions of life.”
(via Brain Pickings)