No bug fix. But a work around at least for me: Setting the ambient volume to 1 in the settings.txt:
ambient_volume=1.000000
And then adjust the volume in Windows and the sliders in the EU Rome sound options as you want. But don't touch the ambient sound slider!
For me then everything seems to work: Different sound at different regions (coast, desert, land...) and different volume of the ambient sound depending on the zoom.