What's the sound when something goes wrong?
It is a dissonant error buzzer — two tones roughly a semitone apart, sounded together so they beat against each other. The unpleasantness is engineered rather than accidental: that interval is one the ear reads as an alarm rather than a note, which is why it works as a "wrong answer" cue.
Hear it
Game shows established the convention, and computer error sounds reinforced it. Both rely on the same trick — a small interval, no resolution, and an abrupt cut-off.
There are two distinct sounds people mean by this. One is the game-show buzzer, flat and sustained. The other is the operating-system error chord, which is shorter and has a definite pitch. They are not interchangeable: the buzzer reads as a judgement, the chord reads as a malfunction.
Cut it hard against the last syllable of whatever was wrong. Any gap and it reads as a separate beat rather than a correction.
Commonly called
People search for this under a lot of different names — all of these find it here: