Cut a 6mm cube from a piece of rubber eraser.
Place the cube below the bridge in between the strings above the felt dampener. You may want to experiment it with varying positions and varying thickness of the dampener. (Or even remove the dampener completely)
I tried it and yes it does reduce wolf tones and noise of the Erhu. But like the Rubber band trick, I felt that it removes the edge in the tone. And someone who tried it commented that the timbre of the tone is flattened.Apparently "All good cellos have wolf tones" so they say. There was a discussion on the net about a Stradivarius cello with a terrible wolf tone as well.
I don't know if the same applies to the Erhu. But that is sure a good way of consoling yourself if you got a Erhu that howls.
