Image showing dial-up modem "handshake" noise explanation

You might remember that weird sound dial-up modems made from back in the day, that unmistakable “EEhhhhhh awwwwwwwooooo BHSSSHHHHH” Well it turns out that’s just your modem and the server talking to each other in what’s called a “handshake.” You might remember about 15 seconds into the sequence it starts making a chaotic hissing….that’s where it would start transmitting more information over the phone line, sounding to humans like hissing noise. It’s wild to think this sound was two machines physically talking to each other! Now most of that “talking” is done 100% digitally over airwaves or light signals, so they no longer make that weird noise. Also the speed which a “handshake” now occurs is milliseconds rather than 20 seconds.