For some combat veterans, the Fourth of July is not a time to celebrate the independence of the country they love. Instead, the holiday is a terrifying ordeal. That’s because the noise of fireworks — loud, sudden, and reminiscent of war — rocks their nervous system. Daily fireworks in many U.S. cities in recent weeks have no doubt been interfering with the sleep and peace of mind of thousands of veterans. This reaction is not unique to veterans with post-traumatic stress disorder, or PTSD.