Accurate measurement of flue gas velocity is crucial for safe production, energy saving and emission reduction in power plants. In this paper, a real-time flue gas audio-range velocimeter was developed using a novel sonic driving mode, quadratic-convex frequency sweeping. Both numerical analysis and in situ experiments were conducted which had validated the developed velocimeter. The accuracy and robustness of the developed velocimeter was quantitatively assessed by root mean square error (RMSE) and standard deviation (SD) from the tests data. The test data was intentionally contaminated with varied levels of noises, forming sets of measurement data with varied signal-to-noise ratios (SNRs). The simulation results show that within the variation of SNR from 0 dB to -18 dB, the averaged relative RMSE obtained using this proposed quadratic-convex driving mode is 1.2 dB and 2.3 dB lower than those obtained using linear and quadratic-concave driving modes, respectively. The experiment results indicate that the RMSE and SD values based on the quadratic-convex driving mode are less than 0.1 for each given SNR. Compared with the traditionally adopted method of linear frequency sweeping, the proposed sonic driving scheme can significantly improve the accuracy and robustness of flue gas velocity measurement. © 2001-2012 IEEE.