How does an ultrasonic rat repeller work? - briefly
The unit projects ultrasonic pulses at frequencies rodents find painful, disrupting their hearing and nervous systems and driving them away from the treated space. Continuous operation and periodic frequency variation prevent the animals from becoming accustomed to the sound.
How does an ultrasonic rat repeller work? - in detail
Ultrasonic rodent deterrents emit sound waves at frequencies above 20 kHz, beyond the range of human hearing. The device contains a piezoelectric transducer that converts electrical energy into rapid vibrations, generating acoustic pressure pulses. These pulses propagate through the air as a narrow‑band ultrasonic signal.
When a rat detects the high‑frequency oscillations, its auditory system registers the stimulus as an intense, uncomfortable noise. The animal’s cochlear hair cells respond, producing a physiological stress response that includes increased heart rate and agitation. This aversive reaction prompts the rodent to vacate the area to avoid prolonged exposure.
The effectiveness of the device depends on several technical factors:
- Frequency range: 20–50 kHz, chosen to match the peak hearing sensitivity of rats while remaining inaudible to humans.
- Intensity (sound pressure level): typically 90–110 dB SPL at the source, decreasing with distance according to the inverse square law.
- Modulation pattern: many units employ intermittent bursts or frequency sweeps to prevent habituation; constant tones allow the animal to adapt and ignore the stimulus.
- Coverage area: determined by the transducer’s directivity and the acoustic attenuation of the environment; obstacles such as walls and furniture reduce effective radius.
Power is supplied by mains electricity or batteries, feeding a driver circuit that shapes the waveform. The driver may include a timer or motion sensor, activating the emitter only when movement is detected to conserve energy and reduce continuous exposure.
In practice, placement of the emitter near entry points, nesting sites, or along walls maximizes exposure to the ultrasonic field. Proper installation ensures the acoustic beam reaches the target zones without being blocked by dense materials. Regular maintenance—checking battery levels, cleaning the transducer surface, and verifying output with a calibrated ultrasonic meter—maintains performance over time.