Do Ultrasonic Pest Repellers Work?

Ultrasonic pest repellers don't work: in controlled tests, plug-in devices failed to drive away cockroaches, ants, bed bugs and mosquitoes, and mice and rats lose interest in the sound within days. The FTC has warned dozens of sellers that their claims need scientific proof, and the devices are still sold with the same claims.

Here is what the research found, why the idea fails on physics and biology, what owners report, and what to do instead for each pest.

What the studies found

University of Arizona Extension reviewed the research in its bulletin Sonic Pest Repellents (AZ1639) and its summary is blunt: scientific studies show commercially available devices to be ineffective. Highlights:

• Cockroaches. Several 1980s studies found no effect. The most thorough tested nine devices against German cockroaches; equal numbers of roaches walked into rooms with and without sound.
• Ants. Kansas State tested three devices on three ant species in the lab and field. None repelled ants; one appeared to work briefly in the lab and then stopped.
• Bed bugs. Northern Arizona University researchers tested four commercial units in choice tests. Bed bugs ended up next to the device as often as on the quiet side.
• Mosquitoes. A device built to sweep many ultrasonic frequencies caused no reaction in two mosquito species. Worse, a Brazilian study of three commercial "mosquito repellers" found bite rates went up by as much as 50% while they were running.
• Rats and mice. The one partial positive: in a 1969 study, rodents showed mild aversion at first, which faded, especially once they found food near the device. They kept exploring the "protected" room even after the food was removed. That's habituation: a sound that never hurts stops being a threat.

The Arizona extension's horticulture bulletin adds that animals caged next to these devices go on living and breeding normally, and that rats and bats in infested attics kept living there with a unit running. Newer "subsonic" boxes that claim to use your home's wiring have tested no better.

What the FTC did

In May 2001 the Federal Trade Commission sent warning letters to more than 60 manufacturers and retailers of ultrasonic pest devices, telling them that claims to eliminate rodents or repel insects must be backed by competent scientific evidence. Between 1985 and 1997 it had already brought cases against six companies, settled by consent orders, over claims that devices eliminated rodent infestations, repelled insects, replaced conventional pest control and cleared fleas from pets. The FTC's own complaints noted that rodents get used to ultrasound and return to nesting and feeding areas. Iowa State Extension republished the warning with its own verdict: there is no research to support the claims.

Why it can't work in a real house

Ultrasound doesn't travel. High-frequency sound is absorbed by soft furnishings, blocked by walls, cabinets and boxes, and drops off quickly with distance. A unit behind a couch protects, at best, the open air in front of it. Mice live inside walls, under appliances and in cabinet bases, exactly where the sound doesn't reach.

Insects mostly can't hear it. Many insects have no hearing organ tuned to these frequencies at all. Spiders and roaches sense vibration through surfaces, not high-pitched sound in the air.

Food and shelter win. A mouse that has found dog food, crumbs or a warm wall void in October has a strong reason to stay. Mild annoyance loses.

Pets hear it. University of Arizona Extension points out that dogs hear ultrasonic sound. Pet hamsters, gerbils, rats and guinea pigs hear it too; that's the whole premise of a rodent repeller. You may be annoying the animals you want to protect more than the ones you want gone.

Verdict by pest

What people who use them say

Owner reports on r/pestcontrol and r/HomeImprovement split in a telling way:

• Pros are unanimous. The most repeated line from technicians: if these worked, pest companies would buy them by the pallet and plug them in at every account. Instead they rely on exclusion and traps or bait. A tech who services food plants and shops put it plainly: mice live in factories full of noise, oil and chemicals; a plug-in box won't move them.
• "It worked for a while." The most common positive report is short-lived: quiet for weeks or months, then mice back. That's exactly the habituation the research describes. Several owners caught mouse after mouse in a snap trap set a couple of inches from an active repeller.
• The success stories usually come with something else. People who say a unit worked often also stuffed steel wool in the gaps, moved birdseed or pet food into metal bins, or simply had a quiet year. A few believe they work against insects such as centipedes and ants, which no controlled test has supported.
• Bats and attics. People who do bat exclusions for a living say repellents and ultrasonic devices don't move a colony; the fix is sealing everything but the main exit, a one-way door, and waiting until young bats can fly (many states restrict summer evictions).
• What finally worked for most: finding the entry points (a common tip is sitting in a dark attic in daytime and looking for light), sealing them with steel wool or copper mesh plus sealant, snap traps baited with peanut butter where the droppings are, and removing birdseed and open pet food.

What to do instead

Mice. This is where most of the money goes, and the fix is mechanical. UC IPM notes mice squeeze through gaps about 1/4 inch tall and 3/8 inch wide, and chew through foam, rubber and wood; seal with steel wool or copper mesh plus sealant, hardware cloth, or metal flashing. Set snap traps perpendicular to walls where you find droppings. See how to keep mice away, how to get rid of mice and mouse traps compared. Peppermint oil is the other popular "repellent" that doesn't hold up; here's why.

Rats. Rats are warier than mice and need more traps, set for several nights before baiting. Find and close entry points, often at the roofline or where utilities enter. See getting rid of rats.

Cockroaches. Bait, not sound: how to get rid of roaches.

Spiders. Vacuum webs and egg sacs, seal around windows and doors, and switch porch lights to yellow bulbs to attract fewer of the insects spiders eat. See getting rid of spiders.

Mosquitoes. Dump standing water weekly and wear an EPA-registered repellent (DEET, picaridin, IR3535 or oil of lemon eucalyptus); see insect repellents.

Squirrels and bats. Exclusion is the only lasting fix, and timing matters for bats because of flightless young in summer. See squirrels and bats.

If you already own a repeller, there's no harm in unplugging it and putting the $30 toward a caulk gun, a pack of snap traps and a tube of bait. For a broader look at what pays off, see our DIY pest control guide.