Spiders do not have ears, but they do have unique sensory organs that allow them to sense vibrations. According to AskNature.org, certain segments of the spider's legs have tiny hairs called trichobothria, which are incredibly sensitive to vibrations both close and far.
The spider's vibration-sensitive hairs allow it to accurately gauge the size, distance and direction of an approaching creature. Using these hairs, the spider can properly prepare itself for a harmful predator, a potential mate or a meal.
Spiders are also able to smell odors using sensory organs called pedipalps, which are located mainly on their legs. The pedipalps also play an indirect yet important role in reproduction, allowing female spiders to attract their mates using scented pheromones.