To cancel the lower-frequency portions of the noise, noise-cancelling headphones use active noise control. They incorporate a microphone that measures ambient sound, generate a waveform that is the exact negative of the ambient sound, and mix it with any audio signal the listener desires.
Esophageal hiatus. In human anatomy, the esophageal hiatus is an opening in the diaphragm through which the esophagus and the vagus nerve pass. It is located in the right crus, one of the two tendinous structures that connect the diaphragm to the spine. Fibers of the right crus cross one another below the hiatus.
An esophageal rupture is a tear in the esophagus, the passageway from the throat to the stomach. It is a medical emergency, requiring prompt diagnosis and treatment. The esophagus may be ruptured by forceful vomiting, chemical injury, trauma or other disorders of the esophagus, such as esophageal cancer. Chest pain from a large tear in the esophagus may mimic symptoms of a heart attack.