What typically happens to noise levels when gear tooth design is optimized?

When gear tooth design is optimized, the primary goal is to enhance the efficiency and smoothness of meshing gears. This optimization often involves refining the shape, profile, and spacing of the gear teeth to ensure better engagement during operation. Improved tooth geometry can lead to a more consistent contact pattern, reducing vibration and the generation of noise.

As the engagement between the gear teeth improves, the impact and friction that typically generate noise are minimized. This not only leads to quieter operation but can also extend the lifespan of the components by reducing wear. Thus, as the design becomes more efficient, the noise levels produced during gear operation tend to decrease, making the choice of decreased noise levels the correct answer in this context. Properly optimized gear design contributes to a smoother, quieter running system, aligning with common practices in power transmission applications.