The only thing I heard of was the sound desensitizing tapes you can get. You play it quiet at first and gradually make it louder so that the dog gets used to it.

Never tried it myself though but read about it a lot. Maybe look it up in google? Having Border Collies means I am familiar with things like this. They have a tendancy to be very sound sensitive. Hate fireworks and thunder etc...Some even freak out at lawnmowers and doors slamming. Mine attack lawnmowers, haha. ...or anything with a similar type engine like motorbikes and such....especially when the rider starts them up. They actually go for the area that contains the engine too. Our Mist used to grab the lawnmower at the edge and actually lift it off the grass. She was a pain when you were trying to mow the lawn.
They also hate pellet guns/air rifles and those devil banger things that kids buy.

Fear of sound often comes on with age with younger dogs often not being bothered but then suddenly developing a fear as they get a bit older.