Snoring is the sound of a clarinet inside the body, with the palate acting as the instrument

Snoring resembles the sound of a clarinet, according to a study that examined how ordinary snoring occurs without obstructive sleep apnea. Air moving through the upper airway can make soft tissues such as the soft palate, uvula and tonsils vibrate, producing a rough, friction-like sound.

Researchers at Sweden's KTH Royal Institute of Technology built a three-dimensional computer model of the upper airway. They focused on the soft palate, the muscular section behind the hard palate. As air moved in and out, it pushed the soft palate, causing the surrounding tissue to move. That movement then altered the airflow, creating a two-way interaction.

The researchers based the airflow on actual breathing measurements from a female patient with snoring but without sleep apnea. Their analysis found that the soft palate continued to vibrate as long as air flowed through it, much like a clarinet reed or a flag moving in the wind. The predicted vibration amplitude at the end of the soft palate was 2.8 to 4.2 millimeters, within the 2 to 8 millimeter range measured by MRI in sleeping patients.

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This study confirmed that snoring can occur solely through self-sustained vibration of the soft palate even when the airway is open and has not collapsed.

The model predicted sound levels of 75 decibels while breathing in and 69 decibels while breathing out. The strongest sound appeared around 90 hertz, consistent with the 68 to 138 hertz range recorded from the patient's soft-palate snoring. The results challenge the earlier assumption that turbulence was the main source of snoring noise. Turbulence accounted for less than 0.5% of the sound in the analysis, while irregular aerodynamic pressure created as airflow pushed and pulled on the soft palate produced almost all of it.

Lead researcher Peng Li said, “This study confirmed that snoring can occur solely through self-sustained vibration of the soft palate even when the airway is open and has not collapsed.” He said the finding suggests that reducing soft-palate vibration or the aerodynamic forces that trigger it could be important in treating snoring. The researchers cautioned that their model simplified the throat into a straight tube 3.8 centimeters in diameter. It did not include sound amplification from the nose or lungs, may underestimate volume, and may overestimate tissue vibration because it did not account for energy absorption. They plan to study how palate stiffness affects tissue vibration and snoring.

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This suggests that reducing soft-palate vibration or the aerodynamic forces that trigger it is important in treating snoring.