If there is a dynamic coefficient of friction between two objects of 0.20, and vibration causes them to be in contact only half of the time, that would be equivalent to a constant coefficient of friction of 0.10. This substantial reduction in friction can have a profound effect on the system. According to anecdote, World War II Panzer tank treads may have been lubricated by their own squeak providing a serendipitous example of acoustic lubrication.