The most common method to evaluate impact sound insulation in buildings, is the tapping machine. One of the issues with the tapping machine however, is that it does not resemble actual walking sound at all. If you have ever visited a field measurement of impact sound insulation, you will probably recognize the hammering noise that the acoustician creates. Another method that is less common, is the so called impact ball. The impact ball might very well be the most expensive ball in the world, with its four-digit price tag (five if you’re swedish)!