America OnlineThe people that gave all those cd's with free internet hours
America Online was a major part of internet usage back in the 1990's and up to the early 2000's.
AOL provided dial-up internet to people all over the world. Dial-up used the telephone to connect to the internet by connecting the computer to a phone outlet. You dialed up your internet service provider with a phone number. This process also consisted of very loud and annoying noises as you connected.
This is the sound of connecting to the internet through dial-up.