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.
Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia. esophageal stenosis. n a narrowing or restriction of the lumen of the esophagus that slows or impedes the passage of fluid and foods from the oral cavity to the stomach. stenosis. narrowing or contraction of a body passage or opening.