Vocal sound waves can still be distinguishable after traveling through walls due to a few reasons:
Diffraction: Sound waves have the ability to diffract or bend around obstacles, including walls. When a sound wave encounters a wall, it can diffract around the edges or through small openings, allowing some of the sound energy to pass through to the other side. This diffraction phenomenon helps in the transmission of sound through solid barriers.
Reflection: When a sound wave encounters a wall, a portion of the wave's energy is reflected back towards the source. This reflected sound can reach the listener, contributing to the perception of the sound even after it has traveled through the wall. Reflections from multiple surfaces can create complex patterns, resulting in echoes or reverberation.
Low-frequency transmission: Low-frequency sound waves, such as those produced by human speech, have relatively long wavelengths. They can pass through solid materials, including walls, more easily than high-frequency waves. The lower frequencies are less affected by the wall's absorption and reflection properties, enabling them to travel more effectively through barriers.
Leakage: Even though walls can attenuate sound to some extent, they are not completely soundproof. There can be small gaps, cracks, or structural weaknesses in walls that allow sound waves to leak through. These leaks may be enough for some of the vocal sound energy to reach the other side of the wall and remain distinguishable, albeit at reduced intensity.
It's important to note that the degree to which sound waves remain distinguishable after passing through a wall depends on various factors, including the thickness and composition of the wall, the frequencies involved, and the distance between the sound source and the listener. In certain situations, particularly with thicker walls or at larger distances, the sound may become significantly attenuated or muffled, reducing its intelligibility.