Converts bark to Hz
Details
$$ \hat{b} = \begin{cases} \frac{b - 0.3}{0.85} & \text{if} ~ b < 2\\ \frac{b + 4.422}{1.22} & \text{if} ~ b > 20.1\\ b & \text{otherwise} \end{cases} $$
$$ hz = 1960\frac{\hat{b} + 0.53}{26.28 - \hat{b}} $$
References
Traunmüller, H. (1990). Analytical expressions for the tonotopic sensory scale. The Journal of the Acoustical Society of America, 88(1), 97–100. doi:10.1121/1.399849