Just about all witnesses of aircraft accidents say they hear spluttering, the noises as the aircraft descends and inevitably hits terrain will cause all sorts of noise distortion and be caused by a lot of things unrelated to power loss. Have to remember this is in a valley where noises will echo around as well.
Just to add to how silly a night departure at this airport is; elevation 935 feet. The hills to the south end about 3km, and directly east and west are around 2500-3000ft, to the North above 3000ft. Mount Buffalo to the West within 10km is above 5500 ft. Then not too far to the east are the highest range in Victoria above 6500 ft. Very little lighting of any hills in the area and lots of trees and rocks. Great scenic valley flying by day, but at night...
I hope it's not another case of having all the toys fitted and thinking I can quasi IFR down valleys using moving map displays. It might be that SI/Engine failure saved his life by putting him in the fields before the mountains.