What you’re hearing is the way 20th century technology tunneled through a 19th century network

digital, analogue, audio, noise, history, technology, sound, modem

Of all the noises that my children will not understand, the one that is nearest to my heart is not from a song or a television show or a jingle. It’s the sound of a modem connecting with another modem across the repurposed telephone infrastructure. It was the noise of being part of the beginning of the Internet.

http://www.theatlantic.com/technology/archive/2012/06/the-mechanics-and-meaning-of-that-ol-dial-up-modem-sound/257816/