Wood is very porous and reacts to temperature and climate. Humidity, heat and cold can affect wood. The change in temperature causes the wood to expand and contract throughout the day. When this happens, the wood creates a sudden creak.
Steam lines and heating water lines make loud noises. It depends on how it was done. It can be small cracks or cracks in wood if it was built a hundred years ago. Most likely, it will creak at the joints if it was built with metal bolts.
Thanks for the question. We also saw a video of the problem you sent us (although it doesn't show what is being done to cause the noise or if there is a lot of movement). The noise is quite loud and not what you would normally expect from a modern timber-framed house. In order to comment correctly, a site visit would be necessary and the floor would have to be lifted and then inspected by an expert in wooden frame houses.
I suggest you fix it as soon as possible. The most common reason a home makes noises is temperature changes in the air, or what is known as thermal expansion and contraction. Temperature changes cause the wood, metal, and other materials in the house's structure to expand and contract, producing ominous creaks. Assuming your home is relatively new, the woods in your house are drying and shrinking, but they are shrinking inconsistently and, yes, they are actually forming new cracks.
Let's be clear that this is not a problem inherent in the wooden structure: a poorly constructed structure is poorly constructed, whether in wood or masonry. The woods dry quite slowly, at a rate of about an inch thick per year, so a 10 by 10 wood will dry completely in about 5 years. I don't think they're trying to explain or defend bad practices in the construction of wooden structures (if that's what happened here), quite the contrary, I think.