This is volatility adjusted WPR (Williams Percent Range). Volatility used for adjusting is the "simple volatility" (no need for it, it is already incorporated in the code of this indicator)
There are 2 deviations compared to original WPR:

PS: an example why the smoothing seems to be necessary for WPR. 3 instances of WPR :
Directional smoothed momentum
Directional smoothed momentum (momentum of averages)
Hull levels
Hull levels