A short descending double buzz with a low-passed edge, so it reads as "no" without being harsh on cheap laptop speakers. Use it for failed form submissions, rejected uploads, wrong passwords and disabled actions.
square 196 Hz (G3) 90 ms, then a 28 ms gap, then square 147 Hz (D3) 210 ms low-pass 1400 Hz, Q 0.9 to shave the harsh harmonics envelope: 2 ms attack, 150 ms decay on the second note