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People in the dog community are worried that sounds we can’t hear might be bothering our dogs. But we can’t check for ultrasound with consumer equipment, even smartphones, because consumer microphones don’t detect sound above 20,000 cycles per second (20,000 Hz). They have no reason to, since we can’t hear in that range. But dogs can. They hear up to 45,000 Hz or higher.

My Search for Ultrasound

In 2023, I bought an ultrasound microphone and learned how to interface it with my equipment. In January 2024, I published a post with instructions on how to check your home and environment for ultrasound that your dogs might be able to hear. I found that many ordinary noises had an ultrasound component—things like clickers, keyboard strokes, motors, even barking dogs. But I was looking for duration or intermittent ultrasound that might be generated by electronic devices and didn’t have a component audible to humans.

I didn’t find any for a while, but I kept searching. You can see my list of items that didn’t emit detectable ultrasound below.

I recently checked the sound environment again, and found some constant, low-level, electronics-generated ultrasound in dogs’ hearing range that was not accompanied with anything in the human hearing range.

I found what people have been worried about: sound that dogs can hear but we can’t. But the sound was very quiet; it would likely be inaudible unless a dog was very close.

This ultrasonic noise was emanating from ordinary AC/DC adapters. I have at least 20 of these in my house. I found three that put out a high-frequency noise that was outside of humans’ hearing range. These were the adapters for:

• A floor lamp with a 24 V DC power supply. It put out a group of frequencies peaking around 21,000, 31,000, and 43,000 Hz.
• A decorative “Moon” lamp with a 12 V DC power supply. It put out a group of frequencies peaking around 23,000, 28,000, and 33,000 Hz. This adapter even put out a little sound when the lamp was off, but more when it was on.
• A Fi GPS collar charger that output 5 V DC. The USB adapter put out a band of frequencies peaking around 22,000, 30,000, and 45,000 Hz.

Note that it was the adapters, not the lights or the charger putting out the sound. I spent a lot of time pointing my microphone at the wrong ends of things!

The following image shows the ultrasound put out by the adapter of the floor lamp. The x axis is time and the y axis is frequency. You can see blue and green bands in the 20–70 kHz range that correspond to the peaks I listed above during the periods the lamp is on. Also note that there is no change in the sound output lower than 20 kHz when the lamp is on. That means that we humans can’t hear the adapter. (The thin vertical lines were created by the click of the remote for turning the lamp on and off.) For more information on reading this kind of diagram, see the page of examples that accompanies this post.

I found one more item that had a constant, quiet, high-frequency sound in the human hearing range plus sounds in the ultrasound range. These sounds were coming from a battery charger for a Dremel tool (8220). It put out an audible tone at 6,000 Hz, and harmonics (mathematically related higher tones) at 12,000, 18,000, and 24,000 Hz. The charger itself (the part where you insert the battery, in this case not the wall plug) has a built-in AC/DC adapter.

AC/DC Adapters

AC/DC adapters function as power supplies for devices that use direct current and lower voltage than what our wall outlets provide. They are the things that often annoy us by taking up more than one space on a power strip. They are often referred to as wall warts because of their bulk. That makes them easy to locate in your home. Two of my culprits were wall warts, and one had a profile almost as small as a normal AC plug.

What Do They Sound Like and How Audible Are They to Dogs?

Here are recordings of the sounds, digitally altered to make them audible to humans. There is some unavoidable distortion, but you can get the general idea. To create these sounds, I did the following:

1. I recorded the sound in WAV format using my Dodotronic 192 kHz ultrasound mic attached to my iPhone 12 Mini using the free Ultrasonic Analyzer app.
2. I imported the audio file into the free sound software Audacity on my Mac.
3. I applied a high-pass filter to isolate the ultrasound.
4. I amplified the signal. The sound was so quiet that I needed to amplify it to be able to see on the screen where the device was on and where it was off so I could edit. See this image.
5. I changed the pitch to bring it down to human hearing range.
6. Sometimes I amplified again.
7. I exported the file as an MP3. The limitations of MP3s don’t affect the sound quality needed for these recordings.

Floor Lamp

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“Moon” Lamp

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Fi Collar Charger Plug

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All the original sounds have ultrasound components in dogs’ hearing range, between 20,000 and 45,000 Hz. But the adapted versions are amplified in the above recordings; in all cases, the original sounds were much, much quieter.

For those of us who are concerned about them possibly bothering dogs, there is a blessing. Ultrasound waves are tiny. For instance, the wave that corresponds to the frequency of 25,000 Hz is 14 millimeters, or a little more than half an inch long. For comparison, a 60 Hz wave such as we could hear in a thunderstorm is 5.7 meters or almost 19 feet long. The tiny ultrasound waves don’t travel far over distances because they are reflected and absorbed so easily. It’s a good bet that even dogs don’t hear sounds such as the ones I presented above unless they are close to the source. The sounds are not blasting through whole rooms.

The two lamps are within about 2 meters of where Lewis sleeps on my bed. While recording, I moved the ultrasound mic from the lamp’s power adapter toward where Lewis sleeps. The mic stopped being able to pick up the sound at about 1 meter. You can see the attenuation of the sound as I moved the mic in this image.

Items I Tested with Null Results

Various scholarly and lay articles include lists of household devices that may put out ultrasound. I chose the following devices from those sources, tested, and detected no ultrasound. Other brands or models of these items might yield different results. Note that some of these items have been reported to scare dogs (Grigg et al., 2021). But noises do not have to have an ultrasound component to do so, and we don’t know if the ultrasound component contributed to the fear response.

• new and old lights: fluorescent, incandescent, LED including ring lights, night lights (which include adapters)
• screens: desktop computer, tablets, laptops, flat-screen TV
• motion-sensitive wildlife camera (Meek et al., 2014)
• laptop fan
• computer power adapters (I was sure I’d find a culprit here, but no. The Apple devices were all silent.)
• power strips
• USB wall plugs (these are also AC/DC adapters). The only noisy one was the Fi collar plug.
• smart plugs (two brands)
• refrigerator, microwave, oven
• smoke alarms on standby (not beeping)
• remote controls (except for occasionally the click of a key)
• ultrasonic humidifier
• space heater
• various fans

A Special Note about Smart Plugs

Because of a viral social media post from November 2023, many people are concerned about the possibility of so-called “smart plugs” putting out ultrasound. While it is possible, neither of the two I tested put out any. I deliberately chose cheap ones, because they are less likely to have strong quality control. An engineer pointed out to me that standard QC includes making sure electronics don’t put out noises such as coil whine or capacitor squeal in the human hearing range. But there is far less concern about the ultrasound range, for the same usual reason. We can’t hear it.

Note that smart plugs are not AC adapters. You might plug an adapter into one, though. Many smart plugs note 2.4 GHz or 5 GHz on the back. Don’t worry; these numbers refer to compatible Wi-Fi types and are not audible sound frequencies to humans or dogs.

Items That Produce Sound That Includes Ultrasound

These are not the stealth items that people are worried about, but I was fascinated to find so many noisy items that included ultrasonic frequencies. I created a page of ultrasound examples that includes images of the output of some of these loud items.

• computer keyboard strokes
• clicker
• ultrasonic squeaker toy
• regular squeaker toy (you can see an image of the ultrasound components of noise from the preceding four items here)
• barks and whines of a small dog (Sibiryakova et al., 2021)
• clicks of various switches (like on remotes to fans or lamps)
• smoke alarms doing a test beep
• computer mouse clicks
• hands clapping
• jingling keys
• hand-held hair dryer
• jingling dog tags
• upright vacuum
• small rotary tools (e.g. Dremel)
• Makita screwdriver and drill
• Makita rotary hammer drill

For some of these items, the ultrasound component was among the loudest of the frequency bands. Because dogs’ hearing is more sensitive in the upper frequencies than ours, if a dog were close to such an item, they would likely hear a louder sound than we do. Most apps that measure volume, such as SPL meters for smartphones, don’t include the ultrasound range.

People frequently ask me about using ear-muff type ear protection for dogs who are fearful of thunder or fireworks. I always explain that such gear can’t protect against the huge sound waves generated by those low-frequency sounds. But these ear protectors can usually prevent the transmission of smaller sound waves very well. If your dog has been conditioned to wear ear gear, it would be a kindness to have them wear it as much as possible for grooming. The hair dryer and rotary tools I checked were loud in the ultrasound range, on top of being loud in high frequencies humans and dogs can both hear. Clippers may also put out ultrasound, but I didn’t have any to test.

“Ultrasound” Is an Arbitrary Definition

It’s crucial to understand that sound doesn’t magically change when the frequency goes over 20,000 Hz. That boundary of 20,000 Hz for ultrasound is derived from “sound that is too high for humans to hear.” It’s a handy distinction, but it’s based on biology, not physics. It’s anthropocentric. Ultrasound is just sound with a higher frequency. I always make the point in my sound webinars that we shouldn’t assume that a sound is aversive to dogs if it is in the ultrasound range, even though there are some oddball online articles that claim this is so. Keep in mind that dogs’ hearing evolved to function in that range. Many small animals that are prey to canids vocalize in that range. It’s no coincidence that domestic cats can hear in that range and even higher, too.

Anything happening above 20,000 Hz is a mystery to us. But it’s not to dogs; it’s just part of their world. It is quite possible that a constant noise in the ultrasound range could bother some dogs. It’s also likely that many dogs habituate to it, just as many dogs (and many humans) stop noticing other ongoing stimuli. For instance, the furnace is on in my house as I write this. There is the sound of the fan blowing air through the ductwork and perhaps the sound of the furnace itself coming through the registers. But I don’t “hear” these long duration sounds unless I turn my attention to them. Likewise, most of us who live in cities don’t notice the common 60-Hz hum of transformers. But people who live in rural areas may notice it when they come to town. And some people are immediately bothered by some ongoing sounds or never habituate.

I have an example in another post of dogs hanging around during a very obnoxious ongoing sound, even deliberately basking in the sun close to the sound source. This example “proves” nothing about how all dogs respond to sounds. However, it provides evidence that we may not be able to predict their response.

Limitations of My Testing

In the interest of transparency, I have created a separate page that delineates aspects of my home setup that affect the precision and accuracy of my data, in this and other posts that present results. I do not have controlled laboratory conditions. But I include in the list how the limitations were mitigated and why I can be confident in the results I have presented here.

Conclusion

Two major takeaways:

• The “stealth” sounds I found are likely inaudible unless a dog approaches close. Here is a photo of sound-reactive Lewis standing right next to the adapter for the floor lamp while he determines whether I have “webinar or Zoom treats” in a drawer.
• The ultrasound generated by motors can be loud. Properly conditioned hearing protection would be beneficial for dogs undergoing grooming procedures where a hair dryer or rotary tool is used.

Others have found more stealth ultrasound than I have, as described in this dramatically-titled CNET article. However, the author doesn’t discuss the rapid attenuation over distance of ultrasound, nor do they give us a good sense of how loud the sounds are.

I will keep performing periodic sweeps for ultrasound culprits in my area and report any findings.

Supplemental Materials

There are two pages with information relevant to this post:

Copyright 2025 Eileen Anderson

References

Grigg, E. K., Chou, J., Parker, E., Gatesy-Davis, A., Clarkson, S. T., & Hart, L. A. (2021). Stress-related behaviors in companion dogs exposed to common household noises, and owners’ interpretations of their dogs’ behaviors. Frontiers in veterinary science, 8, 760845.

Meek, P. D., Ballard, G. A., Fleming, P. J., Schaefer, M., Williams, W., & Falzon, G. (2014). Camera traps can be heard and seen by animals. PloS one, 9(10), e110832.

Sibiryakova, O. V., Volodin, I. A., & Volodina, E. V. (2021). Polyphony of domestic dog whines and vocal cues to body size. Current Zoology, 67(2), 165-176.