Dial Up Modem Handshake Sound - Spectrogram

I grew up with the bleeping chirps of software loading from 300bps modems and "turbo" C64 tape recorders. I could easily recognize different games from the sound they made when loading, and it is trivial to recognize the various modem handshakes. this video link

In this link this video you can hear an additional sound pattern at the end that is not explained in the article or the image, but I remember hearing it every time I connected via modem. Can someone explain what it is?

Did you know each manufacturer had a unique sound for their v90 handshake? This one sounds like a Lucent WinModem. (Based on listening to the sounds here[1]. Yay for RealAudio!) The USR/3Com modems were two "bongs" (four if the higher speed failed). But I was always fond of the Rockwell sweep[2]. Of course, required reading is HN favorite Oona Räisänen's excellent analysis of a modem handshake. [1] link [2] this video [3] link

3d spectrogram: this video Animation of the picture illustrated in this article: link If you live with someone >= 30, turn up the volume and wait for him/her to appear at the door for a nostalgia moment...

Here's a 3d visualization of a dial up modem handshake sound apparently made using iZotope Ozone 5 (from 2011): this video

However, another major reason is that people have repeatedly gone seeking for language-like or human-language-level behaviors in animals, and repeatedly and consistently failed. It is also worth pointing out that detecting language is a great deal easier than understanding language. Something like this video is reasonably recognizable as clearly some sort of language even if we have no (unassisted) human idea what it is saying. We can tell with quite high confidence that most animal sounds are not hiding some deeper layer of information content. Such exceptions as there are, like whalesong, take you back to my first paragraph, though. The idea that language is a uniquely human phenomenon may be "dogma", but it is also fairly well-founded in fact. It should also not be that surprising; had another species developed language first, they'd be the ones looking around at their surroundings being surprised they are the only ones with proper language, because they'd probably be the dominant species on the planet. It isn't a "humanist" bias, in some sense that humans are super special because they're humans, it's a "first species to high language" bias, which happens on this planet to be humans.