The sound of hammering nails can appear louder when it travels through walls, primarily due to the transmission and amplification of sound waves. When you hammer a nail directly on a surface, such as a wooden board, the sound waves generated primarily propagate through the solid material, and some of the sound energy may be radiated into the surrounding air. However, when you hammer nails into a wall, the sound waves generated by the impact can travel through the solid structure of the wall, as well as radiate into the adjacent rooms or spaces.
Walls, especially if they are thin or made of materials that are less dense or have poor sound insulation properties, can allow sound waves to pass through more easily compared to solid surfaces like wooden boards. The structure of the wall, including its composition, thickness, and any insulation or soundproofing materials present, can affect the amount of sound transmission.
In addition, when sound waves pass through a wall, they can experience a phenomenon known as flanking transmission. This means that sound can travel around or through gaps, cracks, or other weak points in the wall, further contributing to the audibility of the sound in adjacent areas.
It's important to note that the perception of loudness can also depend on various factors such as distance, the materials in the wall, the construction of the building, and the sensitivity of the listener. So, while the sound of hammering nails can be perceived as louder when it travels through walls, the actual loudness experienced can vary depending on these factors.