Ultrasonic Frequencies Explained: What 20–65 kHz Actually Means

Every ultrasonic pest repeller listing quotes a frequency range, but few explain what the numbers mean in practice. If you sell or import these devices, this is the one technical topic worth understanding properly — it is also the question your customers will ask most.

The basic band

Human hearing tops out around 16–20 kHz. Ultrasonic pest repellers work above that line, typically between 20 and 65 kHz. Rodents hear well into this range (roughly up to 90 kHz); insects detect it through different mechanisms. The goal is a sound that is intense and unpleasant for pests but silent to humans.

Fixed vs variable (sweep) frequency

A fixed-frequency unit emits one tone, say 40 kHz, constantly. Pests — especially rodents — habituate: after days of identical, harmless sound, they ignore it. Variable-frequency units sweep across a band (for example 9–65 kHz) so the stimulus keeps changing, which significantly delays or prevents adaptation. This is why sweep models dominate the better tier of the market.

Why pets are (mostly) fine

Dogs and cats hear up to roughly 45–60 kHz, so the low end of some devices can be faintly perceptible to them. In practice, quality devices use output levels and bands that pets tolerate — but cats and rodents like hamsters, gerbils or pet mice should not be kept in the same room, for obvious reasons. Reputable packaging says this plainly; we recommend our clients' listings do the same.

Reading a spec sheet critically

• "Coverage 200 m²" on a 5 W unit — not physically plausible. Realistic per-unit coverage is 15–30 m²; ultrasound is directional and does not pass through walls or furniture.
• Single frequency, no sweep — cheapest to make, quickest to fail in the field.
• Decibel claims at unspecified distance — sound pressure drops with distance; a dB number without a distance is marketing, not data.

What this means for your product line

A credible lineup usually mixes plug-in sweep units for whole-room protection, night-light variants for bedrooms, and high-power or rechargeable units for garages and warehouses. When you source, ask the factory for the frequency range, sweep behavior and per-unit coverage — and expect clear answers. We publish all three on every model page for exactly this reason.