In the Great Pyramid of Giza, in the main chamber, chord F is heard, sometimes under the reach of audibility by the human ear.

Former NASA consultant Tom Danley says the sound could be caused by wind blowing around the ends of the shafts. The resulting effect can be compared to a situation where you blow through the neck of the bottle and it begins to resonate.

These vibrations are sometimes so low that their frequency ranges from 9 to 0,5 Hz. The sound is amplified by the size of the pyramid and of course the main chamber with vanou inside. Danley believes that some of the stones in the pyramid were selected specifically for this purpose.

Source: GizaPyramid.com