Ultrasonic Repellant Devices
Ultrasonic repellant devices are usually small electronic items that either plug into an outlet or run off batteries. They range in price from under $10 to over $600 with pricing factors including the item's range, manufacturer and the pests it is intended to repel. Users can clip the battery-powered devices to their clothing or pet's collar.
Claims
Ultrasonic repellant manufacturers claim their devices emit a high-pitched sound that disorients spiders and other pests, keeping them from entering a home. This offers home-owners a low-cost, poison-free way to keep spiders out. Depending on the product and the manufacturer, these items claim to repel spiders, birds, silverfish, cockroaches, fleas and even bats.
Effectiveness
Unfortunately, most of these devices are nowhere near as effective as they claim. Kansas State University performed a test in 2003 that proved the ultrasound technology was not effective against the pests it claimed to repel. Louisiana State University Agricultural Center's Department of Entomology did a study in 2006 that tested the ultrasonic devices against a different type of pest, the German cockroach, and found they were ineffective.
Pest Control
Because ultrasonic devices do not repel spiders or other pests effectively, homeowners have to take additional steps to protect their homes. Make sure you seal up all the spots where pests can enter the home. Spiders can fit through holes and cracks that are almost invisible to the human eye, so you have to take secondary precautions. Put out boards with glue on them or purchase sticky traps that trap pests on the surface and hold them in place until you can dispose of them.