How can I turn down the volume of the turbo whistle?

In the previous version, I believe there used to be a .ogg file within the game files that can be opened in audacity and the volume of the turbo can be turned down. I can't seem to find it in the new version, 0.9+. Is there any way to turn down the turbo whistle volume? I feel that it is too loud and it hurts my ears after a while.

 

Thanks a ton!