In Qiangang Village, 8 kilometers southwest of Cixian County, Hebei Province, there is a tall tomb of Yuan Shan, the emperor of the Eastern Wei Dynasty, commonly known as "Tian Zi's Tomb" by local people. It is a representative of the tombs of the Northern Dynasties and a national key cultural relic protection unit. For many years, the tomb has been a mound tomb with a height of 50 meters and a diameter of more than 120 meters.

Climb to the commanding heights. 199 1 year, a tomb climbing step was built on the north side of the tomb. 1995, Guanyin was built on the top of the tomb.

Pavilion, from then on, there was strange music. Visitors can hear the sound of "Ding Dong" dripping up and down the steps, such as setting off firecrackers on the steps, especially the sound of water. Form a rare spectacle of "underwater sound steps". Some musicians have found that seven-degree syllables can be distinguished in underwater sound, which is called "music step".

The mysterious "underwater sound steps" attracted a large number of tourists. Due to the lack of scientific explanation, opinions vary. Although many experts and scholars agree that there is no water in the tomb and the underwater sound is only a superficial physical phenomenon, why are the steps in other directions silent, only this step is audible, and there is no scientific explanation.

A few days ago, some experts from Hebei Institute of Engineering visited again and found that the mystery of underwater acoustics lies in the uniqueness of building steps. The whole step is 23.9 meters high and 5 meters wide, 109 steps, making an angle of 50 degrees with the ground. The steps are made of blue bricks and white ash, and the rough surface is not polished, forming equidistant and uniform lime grooves, like keys, thus forming multiple uniform acoustic reflection and refraction surfaces; In addition, there are rough blue brick guardrail walls with a height of 1m on both sides of the steps, and the Guanyinge building with hard mountain cornices and gray tiles on the upper right of the steps has also formed a number of uniform acoustic reflection and refraction surfaces on its roof. The above three unique architectural structures constitute a special environment for repeated reflection and refraction of sound waves, which makes the footsteps on the steps produce a variety of sound waves in the process of propagation, forming a high-frequency chorus, thus deepening the low-frequency footsteps into high-frequency water droplets.