Blast tests were not necessary for the NFL. Practically everything else was. The headsets were dropped repeatedly from 3 and 6 feet onto concrete after being stored at long periods at minus 55 degrees Celsius. Then they were taken to grass and turf fields where testers repeatedly spiked the headsets. They were tested in wind tunnels to see how much the noise would be picked up by the microphones on the mouthpieces. They were tried in rooms with intense reverberation and also in rooms with none at all. They were tested in some stadiums, including Penn State's. They were placed in a temperature chamber. (Cold is more of a concern than heat because plastic becomes brittle at very low temperatures -- special resins used in the space industry were deployed to ward off that risk.) The clamping mechanism that holds the headset in place had to be designed for a consistent fit, so that the headset would fit the same over a baseball cap like Tom Coughlin wears in warm weather to the ski cap and hoodie that Belichick wears under his headset in Foxborough's winter. The ear cups were angled at 15 degrees, because that most closely mimics the angle of the ear.