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.
Just before the esophagus gets to the stomach, it travels through your diaphragm. The diaphragm is a broad muscle that separates your stomach from your chest cavity. The opening in the diaphragm where the esophagus travels through, is called the hiatus.. You'll hear more about the hiatus, and how it can be associated with GERD, a little later. The esophagus then joins the stomach at the lower esophageal sphincter, also called the LES..