What is it that you often hear marbles falling upstairs?

It is said that the old house is a precast slab, and the cement or steel bar inside is deformed? Let's talk about common sense first. Under what circumstances will cement and steel bar deform? Generation after generation, under the influence of air humidity, environmental temperature, external force (such as gravity) and self-aging, the cement of precast slab structure will peel off and the steel bar will be slightly deformed, but will the cement peeling produce bouncing beads?

Or in other words, the elasticity (toughness) of cement is the same as that of rebound ball? Has anyone heard the joke that cement can rebound when it hits the ground? Second, this kind of thing is not accidental. Many friends have had it. Some live on the top floor, and their voices are obvious, usually in the middle of the night and occasionally in the afternoon. This situation is not bad. Confucius once said, "Son of ghosts and gods, stay away from them!" Many things can't be explained by our current science!

An ordinary ceiling is supported by two layers of steel bars. In fact, steel bars are not stuck straight in cement during grouting, which may lead to upward or left or right stress accumulation due to the flow and weight of cement slurry, or thin steel bars may generate new stress due to earthquake or foundation deformation after years of building construction.

There is a lamp line outlet at the lower part of the ceiling, which has temperature and air, so mold will gradually invade the cement along the lamp hole. The contact surface between fine steel bar and cement is the most ideal suture place, where mold accumulates and hyphae begin to corrode into surrounding hollow tubes. If the cement around the reinforced bar is corroded to a certain extent, the hollow pipe will rebound, which is the marble sound source.

Therefore, the next experiment is to deliberately make a cement block, clip a plastic rod slightly thicker than the steel bar in the middle to form a hollow channel, take out the plastic pipe and insert the steel bar after the cement is half dry, and then pour some cement from the other end to fix it. The results show that the sound produced by the movement of thin ribs in the pipeline is most similar to that produced by marbles.

The reasons are as follows: 1. The sound source is not inside the wall, but outside the wall. Considering that many people don't live upstairs, there is only a marble sound. The sound source must be in the wall, because the things in the wall are cement, water pipes, steel bars and wires. This is the only logical explanation since thermal expansion and contraction are excluded.

Because there are a lot of steel mesh below, people can always hear the sound from the ceiling. Upstairs, if they want to hear the sound coming from the ground, their ears may be just close to the ground at that time, which is much less likely, because it turns out that the sound insulation effect of thick cement is stronger than expected. If there happens to be large pieces of furniture on it, few people will stick things on the ceiling, and tiles or wood are often stuck on the floor, which will hinder the transmission of sound. Maybe it's because some people are lucky when they make their beds and sleep.

3. This once again explains why almost no one has heard the sound of marbles coming from the wall, because most of the partition walls are made of bricks without steel bars, so the probability is very small; Even if you hear it, you will feel that there are nails next door. There is nothing special to pay attention to, remember.