Impulse Sounds and the Startle Response: Why Some Dogs Fear the Clicker Sound

In 2018, I wrote a post titled “My Dog Is Afraid of the Clicker. What Should I Do?” I told the sad story of how I scared a dog with the clicker, then scared her even more by following the standard advice to remedy the situation. In the post, I did something I rarely do, which was to give straight-up advice. I advised people whose dogs were afraid of the clicker to switch to a verbal marker if they really needed a marker, and to leave the click sounds alone for a bit while they determined the extent of the dog’s fears.

I stand by that advice. And now I am going to show you why switching to a quieter mechanical click is not enough of a change to remediate some dogs’ fear.

It’s been great to see more research on training with and without the clicker and the comparison studies rolling in. Many people would be surprised at how many studies of markers, bridges, and secondary reinforcers have been made over the years. I’ve been keeping a spreadsheet of them for quite a while now. For instance, it’s often said that the click sound has special properties in that it is processed by the amygdala. But it turns out that the amygdala is involved in reward expectation and the processing of all predictors and secondary reinforcers—not just the click sound. There is research on this dating back to at least the 1980s.

People have long speculated that the clicker has special effectiveness because the sound is unique. Its short duration and salience seem to help with precision. But do you know what I have never seen? An analysis of that sound compared to other sounds. How long is it, really? What kind of sound is it?

I’m going to show you. Then I’m going to put forth some ideas about the ramifications.

How Can We Communicate about Sounds?

We don’t have enough words in English to describe sounds. As an auditory-oriented person, I run up against this problem a lot. Here is one thing that helps a little. Waveform diagrams allow us to translate the aspects of a sound wave into a visual presentation. So I’m going to give you some examples of what various sounds “look like.” We’ll examine their amplitudes (volumes), rhythms, and onset times graphically over time.

Instead of talking a lot about it, I’m going to show you a lot of examples. You’ll get the hang of it soon enough.

Examples to Get Started

The x-axis (horizontal) is time in seconds. The y-axis is amplitude (volume). I am not including details for the y-axis. These would properly be in decibels. But because these sounds were recorded in different situations, I didn’t control for the distance between the sound source and the mic. Giving readings in decibels would be misleading. I want you to look at the shapes. (If you are curious, the y-axis is on a linear scale to help the user know their recording level. Several of the click sounds “saturated” the scale, meaning that their volume exceeded the bounds of the scale at the distance from the microphone I used. Bad audio engineering behavior on my part!)

I’m not going to get into pitch, because if there are many different frequencies playing at the same time, we don’t hear pitch at all. Most of the sounds I’m going to show you are of this variety. For the piano and violin, the frequency is too high for us to see individual oscillations at the given scale on the page. But most of the sounds are too complex to show oscillations at all.

Here is the C above middle C (C5) on a piano, played at loud, medium, and soft levels. Note how the sound starts off very suddenly (the piano is actually in the percussion family of instruments). Even the very soft one has a definite beginning. Then the amplitude decreases (decays) quickly over time on each one.

Here is the same C played on the violin. String instrument sounds played with a bow don’t necessarily decay. This particular sound starts abruptly, but stringed instruments can also fade in.

Here is what talking looks like. (This is the image of me saying, “Here is what talking looks like.”)

Here is a chainsaw being used to cut down a tree. The last shape is the tree falling.

OK, now we get to the good stuff, the point of this article. I want to show you what the sounds of the clicker and other mechanical markers look like.

Impulse Noises

The following noises are all what acousticians call impulse noises. An impulse noise goes from zero to a high volume in such a short time that it is perceived as instantaneous. Impulse noises are likely more common in human society than in nature. Sudden thunderclaps are impulse noises. Natural explosions can be. But humans create all sorts of impulse noises. Exploding gasses, mechanical impacts, and explosions are impulse noises. Digital noises that are not deliberately faded in, but just “turn on” can be impulse noises. Noise is well studied and regulated by OSHA and the CDC because it can be harmful in several kinds of ways. For instance, very loud impulse noises can cause ear damage because of the suddenness, whereas a gradual noise that peaks at the same volume would not.

You may suspect what I’m working up to. Even though these sounds are quieter, clickers and other mechanical markers have the other characteristics of impulse noises: sudden, with a very fast onset. They are of the mechanical impact type. The suddenness is one aspect of their precision. If you want a short marker, you want it to start (and stop) fast. Here are some examples.

Here is the pop of bubble wrap. Check out the time scale: the loud part is over in less than 1/10 of a second. The loud part is about 0.07 seconds, or 70 milliseconds. I’m going to use milliseconds from here on out. Just remember that 1,000 milliseconds comprise a second.

Here’s the click of a dog’s plastic buckle collar. Hmmmm, imagine that right next to your ear.

Here is a box clicker. The two clicks are about 110 milliseconds apart.

Here is a “bug” clicker. This one was a little harder to do quickly so the two clicks were about 160 milliseconds apart.

Here is a baby food lid. Note: I learned that they are very unwieldy. Trying to click with a round disc that keeps slipping out of your fingers is not practical! The amplitude is also very different, with the second click much quieter. These clicks are about 100 milliseconds apart.

Here is a retractable ballpoint pen. I had never noticed that the second sound is louder than the first one, but it is. These clicks are about 170 milliseconds apart. You’ll see in a minute why I’m mentioning the time between the clicks.

Less Abrupt Sounds

All those clicking sounds started very abruptly. Here are some verbal sounds and a mouth click for comparison.

Here’s the verbal marker “Yip.” It is about 110 milliseconds long. But look how gradually it starts compared to the clicks above.

Here’s a verbal “Yes.” It also starts gradually and is about 150 milliseconds long.

Here is a mouth click. It is about 75 milliseconds long.

Onset Comparisons

One of the characteristics of impulse noises is the fast onset of the noise and the quick rise to the maximum amplitude. So for the following images, I zoomed in 10x, that is, we now see the detail in a tenth of a second (100 milliseconds) in the space we were seeing a whole second. This is so we can see the time it takes for the onset of the sound.

Here is the “Yip” zoomed in. It may be only 110 milliseconds long, but almost all of that is the comparatively gentle onset of the Y sound.

Here is the mouth click zoomed in. Even though the mouth click looks a lot more sudden than the verbals in the images above, check it out when zoomed in. It still doesn’t have the almost instantaneous onset of the mechanical sounds.

So we can compare the above with a mechanical sound, here is the plastic buckle zoomed in. The amplitude rises to its maximum within just a couple of milliseconds.

Impulse Sounds and the Acoustic Startle Response

I’ve shown graphically how much faster mechanical clicks start than our verbal noises. Here’s why I am focusing on that fast onset.

Mammals have a reflex called the startle response. It can be triggered by a sudden noise, an unexpected touch, or even a purely visual stimulus (think of a silent jump scare on a computer or movie screen). But it is so commonly triggered by noise that that variety has its own term: the acoustic startle response.

In the startle response, the body responds with a rapid extension, then flexion of several muscles. (In humans, these often center on the head, neck, and shoulders, but also extend down to the legs. The eyes blink and the jaw tenses. You probably can summon the kinesthetic memory of your shoulders tensing when you have been startled. If you were sitting down, the quick muscle movement of your legs made you jump out of your seat a little as well.) The criteria for an acoustic stimulus to trigger a startle response have been studied in several species, although not in dogs that I can find. The criteria to acoustically evoke the startle response in rats are 1) that the sound reaches full intensity within 12–15 milliseconds (0.012—0.015 seconds) of its onset, and 2) that the sound is about 80-90 decibels (Ladd et al, 2000). Many texts note that quick onset is essential to the startle response. If a sound is equally loud at its peak but takes more time to rise to that volume, it won’t trigger a startle.

With the onset criteria in mind, take another look at the zoomed-in image of the buckle collar. The time from onset to maximum of that sound is well under 12 milliseconds: it’s less than 5. On the other hand, the onset of the mouth click is more gradual and does not reach as high an amplitude (volume). Again, the amplitudes are not exactly at the same scale, because I did not maintain an exact distance from the microphone over the time I recorded them. But they are roughly representative of the comparative volumes. The mouth click is indeed much quieter than the buckle collar.

Finally, look again at the zoomed in verbal “Yip.” It takes fully 100 milliseconds to reach the peak amplitude.

The Takeaway

  • While clickers may not quite reach the criteria to evoke the startle response, they come close. A sensitive animal could be startled by a clicker, especially if the click happens close to its ears. Animals can habituate to startling stimuli, but there is a chance that a sensitive animal will instead become sensitized. And a dog who is sound phobic may respond with fear to a click at any volume.
  • If an animal becomes sensitized to the clicker sound, changing to another mechanical sound (jar lid, ballpoint pen) or dampening the original clicker may not work. I’ve tried this with unfortunate results, and I know some of you have, too. I hypothesize that it is because these quieter mechanical sounds still have the sudden onset of an impulse sound.
  • From a bioacoustical standpoint, switching to a verbal marker will generally solve both of the problems. It is quieter, and the onset is much slower than that of a mechanical device.
  • The total time of a quick verbal marker is comparable to the time between the two clicks of a clicker, so you may not be losing much in precision.

Mechanical clicks, even quiet ones, have the characteristics of impulse sounds, which can trigger the mammalian acoustic startle response. If you’ve scared an animal with a clicker, it’s probably wise to move away from mechanically generated sounds until you know more about their particular sensitivities.

These are my own deductions, based on the acoustic properties of mechanical clicks, the nature of the mammalian startle response, and what I have observed in dogs. I’m not saying that clickers are dangerous for all dogs, or even most dogs. I’m saying that some fearful or sensitive dogs will not habituate to these startling noises, that they may get sensitized instead, and that the sensitization can generalize to other similar sounds, even at lower volumes. There could be errors in my assumptions, and I am open to any discussion on the topic.

References and Further Reading

Götz, T., & Janik, V. M. (2011). Repeated elicitation of the acoustic startle reflex leads to sensitisation in subsequent avoidance behaviour and induces fear conditioning. BMC neuroscience12(1), 30.

Ladd, C. O., Plotsky, P. M., & Davis, M. (2000). Startle response. George Fink. Encyclopedia of Stress.(ed), 3.

Rooney, N. J., Clark, C. C., & Casey, R. A. (2016). Minimizing fear and anxiety in working dogs: a review. Journal of Veterinary Behavior16, 53-64.

Yeomans, J. S., Li, L., Scott, B. W., & Frankland, P. W. (2002). Tactile, acoustic and vestibular systems sum to elicit the startle reflex. Neuroscience & Biobehavioral Reviews26(1), 1-11.

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Copyright 2020 Eileen Anderson

16 thoughts on “Impulse Sounds and the Startle Response: Why Some Dogs Fear the Clicker Sound

  1. Outstanding – thank you for this! I’d be fascinated to see how my marker word, DING! looks. Dogs seem to enjoy it, not be startled by it. Thank you for this terrific work.

    1. Suzanne, thank you! And if you can send me a link via email to a video where you are using “Ding” (or attach a simple audio recording) I’ll run it through. My prediction: fairly clean start, as the d is a voiced plosive, but a longer end because of the nasal -ing. Contact me on Facebook Messenger if you like and we’ll go further on this.

  2. So interesting! I went back and read your other related posts. I have a dog (yep, a border collie) who is noise sensitive to very specific sounds. She’s fine with clickers and many loud noises, including chain saws, tractors, tile saws, engines, etc. Mildly afraid of thunder and fireworks (but esp the screaming kind). Mostly afraid of metallic noises: metal file drawers, mail box, oven door, some pans (but not her metal food dish). Lately she has become afraid when I say words that include a “ch”, “sh”, or “f” sound!

    1. Oh my, don’t you hate it when they generalize! And that’s a fascinating generalization from metal to those spoken sounds. Maybe I can look at the waveforms. Are you doing counterconditioning? Access to a veterinary behaviorist? I always worry when I hear about generalization of scary sounds because I watched it with my own dog, even when on meds and doing CC. I was always having to push back, for her whole life. She got to where just about any of the sounds in her “scary” category sent her running to me for a treat, but when we got a new one, we had to do a little work.

      Good luck!


      1. Same problem as Laika (comment below). I’m also a professional trainer and thought I was good at CC, but this dog is so sensitive I can’t find a starting place. I am considering Vet Behav & meds. If you could compare those waveforms (metal vs. spoken “ch” “sh” “f”) I would be so interested and grateful.

        1. Julie I’m sorry, I thought I had answered you already. Could you give me an example of the types of metal noises that you would like for the comparison?


          1. The easiest would be two metal cookie sheets clanking together. Or two metal pot lids clanking. A metal file cabinet drawer sliding and slamming shut is a bad one too, but you might not have that. I have also noticed that she is less afraid of spoken “ch” when my husband says it in his much lower voice. I was trying to say “ch” words in a soft, high, happy voice which didn’t help. Some of the “ch” words are “chin”, “chia”, “chicky”. Thanks, Eileen!

            1. Interesting! Those sounds are pretty disparate, but I’m in! I’ll either post results here or link to them from here.


  3. Eileen, Thank you so much for the clarity and depth of this post. It’s fascinating to think about the qualities of sounds, rather than just their amplitude, in relation to the mammalian startle response and fear learning. FWIW, your hypothesis fits nicely with the facts of my young dog’s life. She is sensitive to all impulse noises, but through careful work had learned to tolerate, even like, the ones we encounter regularly (like harness buckles, and the ever-present annoying beeps of modern life). She was also fine with the clicker. However, a bad experience with a smoke detector early on made a huge impression on her, and sensitised her to that particular sound. One day, over a year later, I decided it was time to work on it: I pulled up a sound file of a smoke detector alarm on my computer, set it to the lowest volume possible in my computer’s speakers, put it on in the far end of the house away from our training room, texted my wife to turn it on :), got out the bacon bits, and started my DS/CC with my dog. About 20 seconds in, it was clear that the stimulus was too intense for her, even though I actually couldn’t hear it. We stopped, I figured I’d regroup and start again some other day. Instead, what happened was that I had already successfully sensitised my dog to impulse sounds from my computer speakers. She generalised to EVERY notification sound, alarm beep in a video or a TV show, etc. Since I work on my computer from home, this was pretty awful. She then generalised over the next week to every impulse sound in her larger environment: clicks, oven timers, silverware clicking on porcelain, buckles, and and… It was a nightmare. With months of careful work, eating with plasticware, and a short course of meds, she recovered her previous tolerance of all of those impulse sounds. And… we now have a smoke detector that is designed to be used by sight impaired and deaf folks: it makes no noise but releases wasabi aerosol and flashes instead. 🙂 Maybe one day I’ll be brave enough to attempt DS/CC to the smoke detector again, but I don’t know! I’m a professional trainer, straight DS is kind of my speciality, and I still screwed it up royally with this dog with disastrous consequences. Thanks again for helping me think through this really important issue.

    1. Oh Laika, I am so sorry!

      I do have a business where I change sounds for desensitization purposes using aspects other than volume. I have been going to work on the low battery beep of a smoke alarm forever. The actual smoke alarm—it would be so hard to ever get all the way to the full sound because of the combination of the scary sound AND the volume.

      My Zani had several bad run-ins with the actual smoke alarm sound during her last year. I set one off when making something smoky in the kitchen. We got through that with baby food. But I had run out the door with the smoke alarm, and forgot and left it outside overnight. Turns out that humidity can set them off, so we had another round. Poor pup. 😞

      I should have switched to one of the alternative ones long ago. I didn’t know about the wasabi!

      Drop me a line if you ever want to chat about this stuff.


  4. Thank you so much for that in depth enquiry, it really helped me to understand why reducing click sounds has never worked well for me and also why I see so many dogs who are or become, scared of the clip buckles on harnesses.
    My previous dog hated clickers (her marker was “smart” in a sing song voice) and oh boy the low battery warning sounds were dreadful…. the fact they could start while I was out or overnight so that I came back to a slobberring wreck made me feel just awful. We tried cc/ds in conjunction with meds but never managed to achieve a resilient result.
    It’s such a relief to now live with a dog who is not noise shy, but my prior experience really helps me to emphasize with those who are still facing those repeated traumas.

    1. Thanks for your comments, Jane. I agree; it really changes your life to live with a dog who is sensitive to these kinds of sounds.


  5. Hi there,

    Thanks so much for this post, which has give me a key to unlock an issue for one of our dogs.

    She’s a nervous rescue with a very sensitive soul. Before she came to us, she had obviously been treated inconsistently, if not actually mistreated. She was frightened by many situations and many things. In two and a half years, we’ve made lots of progress, but some things still spook her.

    In some cases, it’s obvious what the problem is, or was. If you come into a room and she’s sitting on a sofa (which she is absolutely allowed to do) she used to look terrified, run and hide, and start hiccuping (one of her stress reactions). Now, she just looks at you a bit anxiously, with quivering ears, waiting to see what you are going to do, and visibly relaxes when you sit beside her and fuss her.

    But she hated, hated, hated having her harness put on. She’d try to hide, and if she couldn’t, she’d cower in a corner as as small as she could make herself. It broke our hearts, because she needs her harness to go out, and she loves going out! So few things make her really happy that it seems such a shame to make her unhappy first.

    After reading your article, and the difference between a mechanical click, and a verbal “click” I wondered if it was the unexpected harness clicks that were bothering her. She’s always been bothered by a clicker, so we use a marker word for training instead.

    A few days ago, I decided to try saying “click” immediately before I clicked each buckle (all three of them), hoping that would give her some warning when to expect each of the harsher mechanical clicks. I’m delighted to say that it seems to have worked. Each time since, she’s been less bothered than previously, and today, she just stood still with her tail up, while I fitted her harness. I can’t say she was wildly excited at the process, but she certainly wasn’t cowering in a corner either.

    This makes us so happy. So thank you!

    1. Hi!

      I’m so glad to have helped! Great that you have found something that is working for you.

      You probably already know this, but you can also dampen the harness click a fair amount by encircling each half of the buckle with your hand, holding it in your hand rather than with the ends of your fingers. That dampens the noise quite a bit.

      Good luck to you and your sweet rescue, and many happy walks.


  6. Laika – thank you for your smoke alarm insights. Our border collie Rowan can’t handle the random low battery beeps, so we have temporarily disabled the detectors (not a good idea, I’ll grant). I’ll look into the alternative kinds. And Eileen – another fascinating post. Thank you!

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