The characteristic sound of a hiccu

The characteristic sound of a hiccup is the only sign. Sometimes the only symptom is a slight tightening sensation in your chest, abdomen or throat that precedes the sound. They infrequently last longer in normal individuals without any underlying medical problem
Hiccups are repetitive, uncontrollable contractions of the diaphragm muscle. Your diaphragm is the muscle just below your lungs. It marks the boundary between your chest and abdomen. The diaphragm regulates breathing. When your diaphragm contracts, your lungs take in oxygen. When your diaphragm relaxes, your lungs release carbon dioxide.
The diaphragm contracting out of rhythm causes hiccups. Each spasm of the diaphragm makes the larynx and vocal cords close suddenly. This results in a sudden rush of air into the lungs. Your body reacts with a gasp or chirp, creating the sound characteristic of hiccups.