Spiders tune each strand of their web to a specific frequency by making some strands tighter than others so that when something is caught in it, the spider can easily pinpoint where it is. This is also used for determining whether what cause the sound is a food or a potential mate.
Watch the Video from NPR

Spiders tune each strand of their web to a specific frequency by making some strands tighter than others so that when something is caught in it, the spider can easily pinpoint where it is. This is also used for determining whether what cause the sound is a food or a potential mate.

Watch the Video from NPR