Exactly, Dana. Some studies suggest that even low-level ultrasonic noise can be stressful for people and pets. It’s always best to monitor how you and your pets feel.
We’ve had one for a while and haven’t noticed any adverse effects on our family. Still, it’s probably wise to turn it off occasionally to give everyone a break.
I’ve noticed that some ultrasonic pest repellers can emit a faint, high-pitched hum, likely due to imperfect insulation of the ultrasonic frequencies. It might just be a design quirk.
It’s possible that the device is operating at a frequency with an audible harmonic. Even if the primary output is ultrasonic, secondary vibrations might fall into the human hearing range.
In my experience, sometimes the noise you hear isn’t from the ultrasonic emitter at all, but rather from the device’s internal components—like a cooling fan or transformer—that produce a slight audible buzz.
I read that over time, some ultrasonic units can drift from their intended frequency. This might cause them to emit sounds that fall within our hearing range, which could explain what you’re hearing.
It could simply be that your ears are more sensitive to high frequencies. Even though the device is meant to be ultrasonic, the low-level output might still be perceptible if you’re close by.
Environmental factors might play a role too. Sometimes the ultrasonic waves interact with surfaces or the room’s acoustics, creating a sort of ‘beat frequency’ that becomes audible.
I’ve experienced a similar issue—turns out some manufacturers don’t completely filter out all the audible byproducts from the circuit, so you might pick up a slight noise.
Some users have mentioned that ultrasonic devices pulse on and off, and that pulsing can produce an intermittent tone that’s just within the edge of human hearing.
It’s also worth considering that what you hear might be a combination of electrical noise and the actual ultrasonic sound, especially if the unit isn’t of the highest quality.
If the noise bothers you, try repositioning the device. Often, increasing the distance or changing its orientation can reduce the level of any unintended audible emissions.
Sometimes I play the 20khz YouTube repeating videos to see if it rustles up any mice activity and often times I can tell when it’s having an effect. But one thing I don’t know how to explain - there’s this “click” every Time the track repeats - it’s only about 20 seconds and an instant repeat, looped for about 2 hours - whenever it clicks I hear a response “click” or similar noise coming from the wall somewhere. I dont know why the click would make the mouse / whatever create that same sound in response but I never hear it when I’m not playing the track.