Infrasound

Acoustic waves below 20Hz are normally inaudible, but may be experienced as being in a region of high pressure.

2-5Hz range played at 100-125dB may produce difficulty in swallowing and slight post-exposure headache.
2-5Hz range played at 125-137dB may produce chest wall vibration; difficulty in speaking and voice modulation; swaying sensations; lethargy and drowsiness; and post-exposure fatigue and headaches.
5-15Hz range played at 125-137dB may produce middle-ear pain; difficulty in speaking and voice modulation; severe chest wall vibration; severe abdomen vibration and associated feelings of nausea; a falling sensation; lack of concentration and drowsiness; tinnitus; and severe post-exposure fatigue and headaches.
7Hz is possibly the most disturbing frequency, being close to the natural resonance frequency of many of the internal body organs and being the same frequency as the alpha brainwaves.
15-20Hz range played at 125-137dB may produce severe middle ear pain; respiratory difficulties (gagging sensations); nasal cavity vibration; persistent eye watering; tinnitus; sensation of fear; excessive perspiration and shivering; and severe post-exposure fatigue and headaches.