Do Ultrasonic Pest Repellers Work? What the Evidence Says

The short answer: the evidence that ultrasonic pest repellers work is weak. Rodents can hear ultrasound and may avoid a new sound for a short time, but controlled studies and extension specialists generally find they get used to it within days, and the sound does not pass through walls, furniture or insulation. For insects, the case is worse: a systematic review of electronic mosquito repellers found no evidence they prevent bites, and university tests on cockroaches and other household insects have found little or no effect. Outdoor units for squirrels, deer and cats show mixed results that tend to fade as animals habituate. The details matter if you are deciding whether to spend money on one, so here is what the research and regulators actually say.

Part of our Pest Control guide →

In this guide

1. How Ultrasonic Repellers Are Supposed to Work
2. The Physics Problem
3. What the Evidence Says About Mice and Rats
4. What the Evidence Says About Insects
5. What About Squirrels, Deer and Other Outdoor Animals?
6. What About Moles and Gophers?
7. What Regulators Say
8. Why Some People Say They Work
9. Are Ultrasonic Repellers Safe?
10. What Works Better
11. Frequently Asked Questions

How Ultrasonic Repellers Are Supposed to Work

Ultrasonic devices emit high-frequency sound above the range of human hearing, which tops out around 20 kilohertz (kHz) and drops with age. Many rodents hear well into the ultrasonic range, and some insects detect high-frequency vibration. The theory is that a loud, unpleasant or confusing sound in that range will drive pests away without poisons or traps. Plug-in indoor models are marketed against mice, rats, roaches, spiders and ants; outdoor models, often solar-powered and motion-activated, are marketed against squirrels, deer, raccoons, cats and dogs. Some add flashing LEDs, audible alarms or electromagnetic claims.

It sounds plausible, but hearing a sound is not the same as being repelled by it, and several physical and behavioral factors work against the idea.

The Physics Problem

High-frequency sound behaves differently from ordinary sound. It loses energy quickly with distance and travels in fairly straight lines. It does not pass through walls, floors, cabinets, furniture, boxes or insulation, and soft surfaces such as carpet, upholstery and curtains absorb much of it. That creates “sound shadows” behind every object in a room, and mice and rats, which live and travel along walls, behind appliances and inside wall voids, spend most of their time in exactly those shadows. A plug-in unit in a kitchen outlet cannot reach the space behind the refrigerator or inside the walls, which is where rodents nest.

What the Evidence Says About Mice and Rats

Laboratory and field studies on rodents over several decades tell a fairly consistent story. When an ultrasonic device is first switched on, some rodents avoid the immediate area, eat less near it or change their travel paths. Over a period of days to a few weeks, many return to normal behavior, particularly if food, water and shelter are available. Researchers call this habituation. Some studies have found partial or temporary reductions in activity; others have found none. Few, if any, show that a device alone eliminates an established infestation.

Cooperative extension services at land-grant universities, which advise homeowners on pest control, generally reach the same conclusion: ultrasonic devices are not a reliable substitute for sealing entry points, removing food and trapping. Rodents are highly motivated by food and shelter, and a mildly unpleasant sound is rarely enough to outweigh a warm wall void next to an open bag of birdseed. Our guide on how to get rid of mice and rats covers the methods that do work.

What the Evidence Says About Insects

Mosquitoes

Mosquitoes are the best-studied case. A Cochrane systematic review, a type of analysis that pools controlled studies, examined electronic mosquito repellents and found no evidence that they reduce mosquito landings or bites. The reviewers concluded they should not be promoted or used for protection against mosquitoes. That includes the wearable and plug-in devices claiming to mimic dragonflies or male mosquitoes. For proven options, see our guides to getting rid of mosquitoes in your yard and EPA-registered repellents for skin.

Cockroaches, spiders, ants and crickets

University entomologists have tested commercial ultrasonic units against household insects, including cockroaches, crickets and spiders, and found little to no repellent effect. Many insects do not hear airborne ultrasound in a way that would make it aversive, and those that detect it, such as some moths, use it to avoid bats rather than to flee rooms. If you have roaches, baits and sanitation are the evidence-based approach; see our roundup of the best roach baits.

What About Squirrels, Deer and Other Outdoor Animals?

Outdoor ultrasonic squirrel repellers and animal deterrents are a slightly different category. Most combine a motion sensor with ultrasonic sound, and many add flashing LED lights or an audible alarm. A sudden stimulus that turns on when an animal approaches is more likely to startle than a constant tone, and that can produce a short-term effect in a garden bed or on a deck.

The limitations are the same, though. Animals learn quickly that the noise and lights are not dangerous, especially squirrels, raccoons and deer in suburban yards where they are used to human activity. Effectiveness also depends on the animal’s hearing range: deer, for example, are not especially sensitive to the high frequencies some units use. Rigorous field evidence for these products is limited. Motion-activated sprinklers, which deliver an actual physical surprise, are generally considered more effective deterrents for cats, deer and herons, and physical barriers like fencing and hardware cloth are more reliable still. If you want to try one anyway, our roundup of ultrasonic animal repellers explains which features give them the best chance, such as adjustable frequency, motion sensing and lights.

What About Moles and Gophers?

Solar stakes that emit sonic pulses or vibrations into the soil are sold widely for moles, voles and gophers. Sound and vibration travel differently in soil, but the core problem remains: these animals live in tunnel systems with plenty of food, and controlled evidence that stakes drive them away is scarce. Trapping is the method most extension services recommend for moles. See how to get rid of moles.

What Regulators Say

In the US, the Federal Trade Commission has acted against marketers of ultrasonic pest repellers. In 2001 it sent warning letters to dozens of manufacturers and retailers, saying that claims that the devices eliminate or repel rodents and insects must be backed by competent and reliable scientific evidence. Separately, the Environmental Protection Agency classifies pest-repelling devices under federal pesticide law as “devices,” which do not require registration but must not carry false or misleading claims. In short, a product being sold widely is not evidence that it works.

Why Some People Say They Work

• Timing. People often install a device at the same time they seal holes, clean up food or set traps. The other steps do the work, and the device gets the credit.
• Seasonal changes. Mice move indoors in fall and activity often drops in spring regardless of what you do.
• Short-term avoidance. An initial effect is real in some studies, so early impressions can be positive before habituation sets in.
• Hard to see. Without monitoring, it is difficult to know whether rodent activity actually fell.

If you test a device, measure honestly. Place a few unbaited, nontoxic tracking spots, like a light dusting of flour along a wall, or use snap traps as monitors, and compare activity for a couple of weeks with the device on and off.

Are Ultrasonic Repellers Safe?

For people, ultrasonic devices are generally considered low risk, although some people, especially children and young adults with sensitive hearing, report hearing a faint whine or feeling discomfort, and some units also produce audible noise. The bigger concern is pets. Dogs and cats hear well into the ultrasonic range and may be bothered by a device near where they sleep or eat. Pet rodents such as hamsters, gerbils, guinea pigs, rats and mice, along with rabbits, are likely to be distressed by units meant to repel their wild relatives; do not use them in the same home. Birds and reptiles are less affected, but watch any pet for signs of stress.

What Works Better

For mice and rats

• Exclusion. Seal gaps larger than about a quarter inch for mice and half an inch for rats with steel wool, copper mesh, hardware cloth, metal flashing or sealant. Check where pipes, wires and vents enter the house, garage door seals and foundation cracks. Our guide to keeping mice out of the house walks through the inspection.
• Sanitation. Store pet food, birdseed and grass seed in sealed metal or heavy plastic bins. Clean up crumbs and fallen fruit.
• Trapping. Snap traps placed along walls, perpendicular to the wall with the trigger facing it, remain the most effective home method. Use many traps at once.
• Professional help for large or recurring infestations, rats in walls or attics, and anywhere children and pets make baits risky.

For squirrels and garden animals

• Hardware cloth cages over bulbs and seedlings, and netting over fruit.
• Baffles on bird feeder poles and squirrel-resistant feeders.
• Fencing appropriate to the animal, such as tall fencing for deer.
• Motion-activated sprinklers.
• Taste or odor repellents applied on a schedule and reapplied after rain.

For insects

• Remove standing water for mosquitoes and use EPA-registered repellents on skin.
• Baits and good sanitation for roaches and ants.
• Screens, door sweeps and sealing cracks to keep crawling insects out.

For a broader framework, our pest control guide covers integrated pest management, which combines prevention, monitoring and targeted control.