In a Y junction where sound waves split into two separate pipes, the total energy of the sound wave remains constant, but the distribution of that energy can change. This means that the loudness (measured in decibels or dB) of the sound can vary after the split, depending on the specific configuration of the pipes and the nature of the sound propagation.
If the two pipes have identical characteristics (e.g., same diameter, length, and material), the energy of the sound wave will split evenly between them. In this case, the sound pressure level (SPL) or loudness in each pipe would be roughly half of the original SPL before the split. This is because the total energy is divided equally between the two paths.
However, if the two pipes have different characteristics or if there are reflections or acoustic impedance mismatches in the system, the distribution of energy can be unequal. This can lead to variations in loudness.
For instance, if one of the pipes is narrower or longer than the other, it can introduce additional resistance or impedance, causing some of the sound energy to be reflected back or absorbed. This would result in a decrease in loudness in that particular pipe compared to the other. The specific attenuation or amplification of the sound wave will depend on the acoustical properties of the pipes and the frequency content of the sound.
In summary, while the total energy remains constant, the loudness of the sound wave can vary after a split in a Y junction, depending on the characteristics of the pipes and the acoustic properties of the system.