What type of gear design has teeth angled to allow for quieter operation?

The correct choice, helical gear, has teeth that are set at an angle to the axis of the gear. This angling allows for gradual engagement of the gear teeth as they come into contact. As a result, the teeth mesh smoothly over a longer contact area compared to straight-cut gears, which have teeth that engage all at once. This gradual engagement is what leads to a reduction in noise and vibration during operation.

Helical gears are often used in applications where quiet operation is a priority, such as in automotive transmissions and various machinery. The angled design not only aids in noise reduction but also provides the benefit of better load distribution across the teeth, enhancing their strength and efficiency in power transmission. The gradual engagement also permits higher speeds and allows for the possibility of carrying heavier loads relative to the size of the gear.

In contrast, straight gears have teeth that are aligned parallel to the gear axis, resulting in more abrupt engagement and consequently more noise and vibration. Crown gears are typically used for specific applications like changing the axis of rotation and do not particularly focus on quiet operation. Hypoid gears, while they do facilitate quiet operation and are often used in differential setups, are different from helical gears in that they involve non-parallel axes and allow for smoother