What factor reduces the noise level of a turbofan engine?

The correct answer focuses on the low gas velocity as a key factor in reducing the noise level of a turbofan engine. Turbofan engines are designed with larger fans that operate at slower speeds compared to turbojet engines. This slower gas velocity reduces the intensity of the noise generated during engine operation.

Additionally, the design of the engine incorporates features such as sound-absorbing materials and noise-reducing technologies, which further contribute to lower noise emissions. The larger fan diameter allows for more efficient airflow, which also helps in minimizing turbulent flow that can cause additional noise.

While the engine design itself is crucial in developing quieter engines, the specific aspect of low gas velocity directly correlates to noise reduction. High-speed flows can create significant sound pressure, leading to increased noise pollution. Therefore, it is essential to consider how reducing the velocity of gases exiting the engine can lead to a quieter performance overall.