The word “beep” is not very old. The onomatopoeic expression of “beep-beep” for a car horn only goes back to 1929, according to the Oxford English Dictionary. And the use of “beep” in the sense of a short, high-pitched sound is first recorded in an Arthur C Clarke science-fiction story in 1951.
The post-war proliferation of electronic devices has allowed a massive proliferation of mid-level warning noises. Once upon a time, bells and sirens were announcements that something fairly major was happening. They might have started a drill or indicated a large and dangerous industrial machine was being started up.
But the modern beep is something different. It’s often a mere “alert”. They still warn and announce but it might be something as mundane as the doors on a train opening. There’s an extraordinary plethora of them. BBC