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My kids get nervous as soon as they even see a hand dryer. They start crying when it's on. I thought they were exaggerating, it never occurred to me that sound levels for kids are different because they are smaller (though it makes complete sense). That, coupled with higher sensitivity to noise and more delicate hearing canals of youngsters kind of make me feel like a bad parent for trying to let them use the dryers anyway (Even though I have long since given up). This kids research proves my kids right, and I am not easily convinced ;) Great accomplishment for I should listen to my kids.

Already an impressive combination of curiosity and perseverance to get a scientific paper published for any non-academic, let alone a 13 year old!!

edit: The absolute worst things are these https://www.ehanddryers.com/hand-dryers/tap-hand-dryers, my kids just plain refuse to wash their hands out of fear of accidentally triggering the dryer

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>> The absolute worst things are these https://www.ehanddryers.com/hand-dryers/tap-hand-dryers, my kids just plain refuse to wash their hands out of fear of accidentally triggering the dryer

Wow, I was recently in an airport bathroom where a young boy absolutely refused to wash his hands. His father was extremely patient and said that he needed to wash his hands. The boy was near tears saying that they would miss their plane. It was all a really strange and illogical situation. Until I read your sentence. I don't know if this is why the boy wouldn't wash his hands, but it makes me realize that sometimes kids have reasons for what they say or do, even if they can't explain it. Reminds me of the hand licking incident: https://news.ycombinator.com/item?id=18842009

I thought I had read all about the hand licking incident and learned not to make presumptions about kids. Today, I realize that the lesson hasn't really been ingrained into me yet.

Thank you for sharing that link. Truly.

One thing to remember is that sometimes it's correct to realy trust your kids even in contradiction to your best assessment of the situation. The hand-licking story is about tactics for diagnosis, but another angle is that (sometimes) it's OK to not understand something, to think your kid is wrong, but to let them have their way anyway. Missing a plane vs dirty hands? Trust the kid, find another solution (grab a towel, wipe hands on pants, take the germ risk, etc), and talk about it later as best you can.

You don't want to let your kid be the boss of everything; you don't want to let your kid ignore your intructions or choose to do something fun instead of necessary work, but if your kid would rather stand there and do nothing while getting upset instead of doing some small work item, they aren't "cheating" you out of anything by getting their way.

Kids have a reason for everything they do. If you don't know the reason, it's because you've failed to communicate with them. Sometimes they don't know themselves, but that's still a kind of communication failure.

There are many things my kids were saying that I only figured out days, weeks or years later. Listen, guide them, let them be, and don't be a helicopter parent.

I'm with the child on those tap dryers. They seem designed to blast any remaining drops of water in the bowl into your face or shirt. Hate the damn things and avoid them now. Maybe the places were using the wrong bowl or something. :)

I saw these for the first time on monday. The first thing they did was blast all the water in the sink into a fine mist and spray it over me. I can't believe that the people who designed or specified these ever used them.

Interesting, thanks for sharing that link. I had a ton of weird tics as a kid which could easily be traced back to the large amounts of prescribed amphetamines I was forced to take under threat of punishment. The solution to the tics was... more punishment.

It took me years to realize things such as, the reason I would chew on my shirt color all day even though I would routinely get sent to the principal's office and publicly embarrased by teachers or beaten at home was just because my jaw would get very tense and chewing motions relaxed it, and my mouth was the Sarah Desert and sucking on the fabric pulled moisture into my mouth.

You too!? I thought I was the only one!

My shirts would be sopping wet in the front and would all have tooth holes from my chewing them, I'd go through a shirt a week nearly.

I wasn't on any meds but my teacher at the time would dole out punishments regularly to me in class. I've put 2 and 2 together before, but I never knew I wasn't alone in this behaviour! Thanks for commenting, this really helped me.

All those poor buttons. And then I come to find out that one popular tip for reducing dry mouth in dry environments is literally sucking on a button.

I wonder how common it really is in young children. Certainly seemed I was the only one dealing with it at several different schools. Is it too late to form a club?

Similarly, I had issues with scratching my nose in public, nail-biting, hair-pulling, picking at scabs, sucking my thumb at night... punished and beaten all the time for it, and some particularly nasty teachers would try to make a public example... come to find out in my adulthood that I have a literal disorder, body-focused repetitive behavior (BFRB) syndrome, which is related to OCD and bipolar disorder and ADHD which I also deal with, and heavily exacerbated and permanently worsened by my forced exposure to intense medication.

Did you outgrow the tics? If so, at what age and what led to outgrowing them?

I still deal with BFRB and I've had a few instances of old tics resurfacing, but a combination of practice and learning much about my disorders and cognitive science has helped me tremendously with everything else, such as nervous tapping, twitching, repetitive audible excitations, speech impediments and the like. I believe even my BFRB will eventually no longer be a problem. They all subsided at different points in my youth, mostly after conscious effort.

When I was first placed on medication at five, I developed a pretty awful tic wherein I would swallow every five seconds. I was sent to therapy and the therapist first thought I was lying to get attention and then thought I was crazy and needed more medication. This tic was causing gastrointestinal distress, dental issues from lack of saliva, and was a major speech impediment for me. My esophagus would get pretty raw. This was my first experience in learning how to deal with these on my own.

One tic that seemed to go away without extended cognitive effort (on account of its lower frequency) was extended periods where I would laugh uncontrollably over nothing for half an hour or longer until I was red in the face and choking for breath and my diaphragm was convulsing. This lasted for a few years until adolescence. My family thought I wanted attention again and would punish me when I couldn't stop at their command. It's honestly insane how some people respond to behavioral anomalies in their children.

Thanks for your response. My son is 9 and he goes through phases of having some sort of tic (throat clearing, head shaking, blinking, etc). They're not too bad, relatively speaking, and no one has really noticed. Or if they do then they probably dismiss it.

His pediatrician said it's likely a mild form of tic and tourette syndrome which often goes away by age 13. We haven't brought it up to him besides once or twice asking if he feels any discomfort. We haven't talked to him about stopping the tics and don't plan to. I hope his classmates continue to ignore it and that they remain mild.

Sorry your experience was not supportive and I hope BFRB does, in fact, go away for you.

I would say that habits are everything, and in some cases, I believe even extreme disorders like schizophrenia can sometimes be caused by bad neurocognitive habits degenerating unchecked.

You're doing the right thing by not making a big deal out of it or making them feel different, but as your son gets older and more able to have these kinds of conversations, it's worth opening a dialogue with them about finding ways to form new habits that break the old ones.

Many of my tics only went away after much effort, and growing up I felt like I had no one to talk to about them. My family didn't understand and I didn't have good experiences opening up to other children about them because they also either thought it was an attention thing or that something was really wrong with me.

At some point your son is going to become stressed by his seeming inability to control his own body and he will want to have positive dialogue about it. He may not have the courage to initiate the conversation though or he may be worried you won't understand. I wouldn't approach it with a bag of tricks but rather learn together with your son and encourage them to pursue better habits when apt. I know for me, accepting my disorders as purely physical and maintaining the belief that I could overcome them mentally was instrumental in my healing.

Good luck! I'm sure one way or another he'll figure it out as long as he is surrounded by positivity.

The Kennebunk rest area in Maine was designed by someone who hates children or is utterly incompentent or both. The diaper changing table is flanked on both sides by 4 loud hand dryers. The icing on the cake is the solitary paper towel dispenser is located ABOVE the diaper table. If you drew the short straw for diaper time, you'll be treated with your child screaming for mercy from the dryer noise AND have people who prefer paper towels dripping their wet hands all over your kid.

In re: "the hand licking incident"

Oh the pathos! If only they had known of the "Six Step Reframe" algorithm (which is actually deprecated now in favor of even more effective algorithms.)

In pseudocode: https://gist.github.com/calroc/4719702

> sometimes kids have reasons for what they say or do

Raising two kids I've come to think that this is almost always the case. The reasons may be based on misunderstandings but they are logically coherent in the context. A lot of times they may have a hard time explaining it, especially when an adult loses their temper because they decide the thing is just a folly.

In my kids' school they are not allowed to wear shoes indoors, but my son refused to take his off and wouldn't explain why to the teachers. It drove them mad, and we got phone-calls and emails telling us this had to stop that he must obey the same rules as the rest of the kids! We spoke to him (without reproach) and slowly we realize that he knows his shoes are expensive (because they are pronation) and it turns out that someone had hidden them before. After we explain to the teachers he is allowed to keep is shoes by his desk as long as they are not on his feet. Problem solved.

It makes you wonder about how teachers are selected and trained in the first place/what kind of behaviors are incentivized that they would not be able to handle a minor situation like this and had to resort to emailing/phoning parents when all that was needed was to just sit down and have a calm chat with the kid.

I imagine teachers don't have the time to have this type of 1:1 interaction with the 25 students in their class. Seems like email/phone communication to the parents is reasonable here. Something like disciplinary action would have been bad though.

I will add that it is 1 to 25 in California, other states vary.

One of the reasons why better ratios help kids is exactly to give this type of individual attention.

Judging by teacher's earnings.. they are probably very badly selected and trained.

> and wouldn't explain why to the teachers.

Looks like they thought to ask him, but a kid's parent will be able to extract better info out of them.

The hand-licking incident is more like /r/kidsarefuckingstupid.

That's not the only reason why children hear more and louder. When you're in your '30s you already have a minor hearing loss, you don't hear all sounds and noises then you did when you were 5. Children see more colours as well.

Also, we hear using the cochlea, a spiral sense organ that sorts sound by frequency. In children the whole thing is much smaller. So they hear much-smaller wavelengths of sound which means higher-pitched sound. As we grow so does the cochlea so we hear lower and lower sounds and lose the sensitivity to the highest-pitched ones?

I'm guessing that hair dryers have a scream in the upper register that adults don't normally hear.

That's very possible indeed. I remember when I was a kid my grandparent's tube TV was making a high-pitched sound that was figuratively driving me insane (maybe generated from the HSYNC frequency, now that I think about it). I couldn't understand how they could bear it but of course when I told them they didn't get it because it was probably way outside of their hearing range. I'm fairly sure that now that I'm in my 30s I couldn't hear it either.

Typically a high-pitched whine from a CRT is from the flyback transformer. I found, when I was a kid, that sometimes a well-placed whack on the CRT's cabinet could temporarily fix the problem.

Nowadays, I have no idea if I can hear that whine anymore or not, as CRTs are quite uncommon. Probably not. Much for the better, as it used to give me headaches.

15Khz colorburst whine. Its amusing how many audio recordings even today show a notch filter used at that frequency, years after there were no CRTs anywhere in the recording process.

There are recordings that really should have had it!

https://open.spotify.com/track/3B4q6KbHbGV51HO3GznBFF?si=Fgy...

https://open.spotify.com/track/6PsISpFaCEKwysPfwO9SfC?si=NQa...

(Or if these whines aren't CRT related, I'd be curious to learn the source).

Flyback, not colorburst. Monochrome sets should exhibit the whine as well.

You might still be able to hear it.

https://youtu.be/8XzNh5U8Jzw

https://youtu.be/rkEQ0b35nzw

https://en.wikipedia.org/wiki/The_Mosquito

> The Mosquito or Mosquito alarm is a hand wound machine used to deter loitering by young people by emitting sound at high frequency, in some versions so it can be heard mostly by younger people.

> The sound was made into a mobile phone ringtone, which could not be heard by teachers if the phone rang during a class.

At 35, I'm still deeply bothered by that sound. Slightly related but in a lot of parts of Ginza in Tokyo, they use a similar sound for repelling rats that I find extremely uncomfortable...

I have read this many times online and i think i must be the only one who for some reason liked that CRT sound :-P

Though it might be that since i really loved computers, i associated it with computers and liked it via association.

I was quite surprised as a young adult when one of my ears couldn't hear cricket chirps anymore. If I laid with one ear against the pillow I could hear them, but if I turned over it was silent. A hearing test confirmed that one ear was deficient.

I'm 39 and I can still hear 15kHz flyback. Not as loudly as I used to be able to, but it's still there.

It's not due to cochlear size, we lose sensitivity to high frequencies because the hair cells slowly degenerate with age.

It's not only due to size...

Does that mean that children also don’t hear deep bass? Is it commonly accepted that young children don’t enjoy the sort of music (e.g. dubstep, drum-and-bass) that employs near-infrasonic notes?

Even as adults, you feel anything below 45hz or so more than you hear it. I am confident that children feel too. But the bass heavy club music ypu describe has an adult cultural element, otherwise missing from most music.

An other thing to consider with deep bass is that, at least in concert/club conditions, you feel the bass with your body on top of hearing it. So even if your ear struggles to capture those low frequencies you'll still experience them somewhat.

This is not true.

The dimensions of the cochlea are basically fixed at the time of birth. As the dimensions of the cochlea are the main contributing factor in what tones are able to be heard, the tonal bandwidths are then set at birth as well (minus hearing loss due to damage as we age). If you are interested in how sound is interperted by the brain, be aware that it is not a straightforward process and takes a bit of research. Still, the cochlea is essentially fixed at the time of birth.

More on how the dimensions of the cochlea determine tonal bandwidths: https://en.wikipedia.org/wiki/Hair_cell

[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970226/

[1] http://www.ajnr.org/content/ajnr/early/2011/09/29/ajnr.A2713...

"Children see more colours as well."

I'd be interested in hearing more about this. I understand the mechanism whereby audio sensitivity is progressively lost but I don't see why getting older would result in seeing fewer colors. Is this perhaps instead that we are less sensitive to color, requiring more photons to have the same color experience, but not actually seeing "fewer colors" in the sense that there are colors that fall off our gamut entirely? That would make sense to me.

discrimation (horizontal) vs sensitivity (vertical)

As we age, we lose some hearing power and visual acuity, for physical reasons on the organs.

As our brains mature, they learn to not discrimate among certain "unimportant" sounds and colors. Adults can't lose the ability to disambiguate among novel language phonemes from foreign languages (as perfectly as kids can), and similarly they lose ability to distinguish similar colors that they learned are irrelevant. This isa tradeoff adaptation, so you can see a shadow gradient as single color instead of a complex spectrum, understand that traffic lights are showing the same signal despite variation in frequency, etc.

On another level, very small children (babies) have poor color vision, because their eyes and brains are still missing basic development.

So it's a curve: newborns have poor hearing and vision tha rapidly improves for a few years and then decays slowly, for both physical breakdown and for mental "optimization"

Children do not see more colors than adults.

The cone cell of the human eye is the main type of photoreceptor that senses differences in light bandwidth, aka color. The dics of the cone cell are tuned to be receptive to certain bandwidths of light. These bandwidths are well understood and do not change as humans age (outside of damage to them)[0]. Humans only have 3 sets of these cones and do not gain or loose new types of cones as we age. The receptive bandwidths of the pigments are set by the biophysics of the molecules.

The perception of color does change as humans age, however. Typically, a newborn cannot yet use their eyes well. They can percieve light and dark, then red, then they can process depth, etc. This learning process takes a few weeks to months[1].

The cognition of color is a very in depth and facinating field. Thus far, it appears that color is a cultural and learned thing, in that if your language does not have a word for a color, it seems to be very difficult to determine the color as a different one from among other colors. Translating the mix of photons that your photreceptors are affected by into usable language is a very complicated process and is not well understood yet.

Fun Fact: The Illiad does not include the word blue and the Bible uses it very rarely as well.

[0] https://en.wikipedia.org/wiki/Cone_cell

[1] http://www.bausch.com/vision-and-age/infant-eyes/eye-develop...

A great podcast on color from radio lab if you haven’t already heard it: https://www.wnycstudios.org/story/211119-colors

In short they specifically go into how we perceive color etc. great show!

You know what really hurts my years? As a child, and even now? Airplane toilet flushes. I always wish there were a 20 second delay so I could hit it, wash my hands and run out of the bathroom.

Agreed. Luckily there is a small delay between pushing the button and it actually flushing. I usually press the button and then cover my ears until it stops again.

Except the button is probably covered in other peoples' pee so I wouldn't touch my ears without washing hands.

Hold a piece of toilet paper to flush, then drop it when bringing hands to ears.

Kids can also be over-sensitive to certain kinds of sounds. This is related to sensory integration and in some people the neural system adjusts automatically, while others might require SI therapy. This over-sensitivity is not due to the volume itself, but occurs later in the neural processing.

I've seen it myself: a child would have no problems with loud music, but any kind of noise (as in, white noise) would be painful. This included hair dryers, vacuum cleaners, some power tools, and sounds of water/sea.

Our local fast food restaurant has one of those. Coincidentally it's also a Dyson brand. They don't work very well. Water and crap gets everywhere!

The Dyson combined tap-dryers are awful, awful products - we have some in newly fitted bathrooms at my workplace. I don't know how they made it out into the world without shame. They're hard to trigger reliably, they blow water everywhere, they're generally cumbersome and unpleasant to use.

I swear by their vacuum cleaners, but none of the Dyson hand dryers are good. The boxy air blade ones are the worst I've used so far, but I haven't seen the tap ones yet.

Even the vacuum cleaners are meh at best. Beautiful from the outside, excellent finish but disappointing performance and features for the price.

We have one and it is like trying to drag a tank around the house into small spaces. Like all Dyson products, it's cleverly engineered and presumably hasn't once been tested with an actual customer.

Their stick vacuums are light, although the battery life is short. They are quite effective but only if you use the right head for the job. There is one head for carpet that is amazing for carpet, but it's terrible for hard floors. There is a head that is great for hard floor, but obviously terrible for carpet.

I love the stick vacuum for cleaning stairs, it's far more convenient than dragging a full size one up/down the stairs. Agreed that the battery life is too short.

Not really beautiful - they're 100 percent plastic and look like a child's toy.

At least put some anodised aluminium somewhere on it to make it look 21st century!

I’ve seen them use fancy metallized plastics in place of anodised aluminium.

But yeah, I guess most Dyson items do look pretty awful.

My secret trick for the air blade dryers is to move both hands in opposite directions so it never turns off.

That's amazing. In a 2 minute promo video with many clips of people washing hands, and many clips of people drying hands, they never show someone washing AND drying hands in the same clip. They know the poducts doesn't work at its primary value-proposition.

https://www.youtube.com/watch?v=PkpP-mEUcAs

I’ve seen articles about Dysons filling the air with dispersed virus.

You are supposed to use water and soap to wash off the crap first.

I haven't seen one of those Dyson pieces of shit without at least some gunk or water sitting near the bottom, not draining or sliding into the airflow. Even if you get everything off your hands, having a stupid plastic device with a deep crevice in an environment with fecal coliform presumably floating around is a _great_ design let me tell you.

>Water and crap gets everywhere!

I've only seen those taps with trough sinks[1], which limits the mess.

[1] https://i.ytimg.com/vi/nZfqFvsuE3s/maxresdefault.jpg

I was in Japan recently and they didn't have the Dyson one but they had very similar models from Panasonic and Mitsubishi and they were much quieter and somehow worked better. We need those.

Can confirm this - the hand driers I've seen in japan were generally pretty small, yet very effective and quiet.

Shoot, I get nervous and feel like crying when I see a hand dryer, and I’m in my mid 30s.

Those devices are literally painful for me to be around. I view them as a scourge and will consider not washing my hands if there’s no soundproofed alternative.

I always think they should just take it down and put up a sign that says, "Too cheap for towels." It won't damage my hearing and will get my hands just as dry.

Let’s not even mention how they always try to justify these monstrosities by saying they’re better for the environment. Insult to injury.

YES!

"This device saves trees"

No, it doesn't. We should be (and AFAIK often are) at the point that paper towel pulp is coming from forests we replant. Also, I don't know, maybe those dryers "save trees" but the paper towels provide a forcing function for someone to always have a couple of ready forests on hand, which seems better?

Yeah, I just don’t buy it. 100% recycled paper towels are a thing. And if you really want to get technical it seems like manufacturing and using those devices consume far more energy. Anyway, glad I’m not the only one shaking my head at these things...

Honest question: Have you tried just vigorously shaking your hands and then letting them air dry? It only takes a couple minutes. Worth the wait to still have clean hands.

Honest question: is there anything about my comment or profile that suggests I’m open to receiving hygiene suggestions from a complete stranger on the internet? It’s not like I don’t know how to have clean hands, just saying.

Actually, it was the part where you stated you considered not washing your hands? And I was honestly asking because most people don't realize how quickly human skin dries. I hate air driers also, but I generally don't use paper towels anymore either unless I'm planning on needing dry hands within a minute of leaving the restroom.

Or, hey, we could go with your interpretation that I'm a raging asshole that thinks you don't know how to wash your hands. Whatever floats your boat.

Sorry. I assumed I was being trolled and reacted accordingly.

I was being ever so slightly hyperbolic in my statement about not washing hands. For the record, I do use the time-honored air-dry, shake-hands-vigorously and/or dry-on-pants methods when circumstances demand.

>is there anything about my comment or profile that suggests I’m open to receiving hygiene suggestions from a complete stranger on the internet?

It's probably that you're participating online in a discussion about hand-dryers, and, by proxy, washing your hands -- and expressing your disinterest in using them (hand dryers) .

It might even be the fact that you've said that you considered not washing your hands all together when posed with no alternative -- a danger to others besides yourself.

I find your tone to be entirely unwarranted and rude.

'Just saying.'

>my kids just plain refuse to wash their hands out of fear of accidentally triggering the dryer

That's probably fine, air dryers make your hands dirtier than if you haven't washed them at all.

https://www.washingtonpost.com/news/to-your-health/wp/2018/0...

same with lawn movers, the sounds and vibrations hurt kids. I couldn't stand using one until about 15 or 16.

My kids had a pathological fear of the automatic flush toilets when they were little. They were so loud, and they considered them out of control.

Who would have thought Hand Dryer buyers would have such a nice ecommerce website to shop on!

I wish every ecommerce store looked as good and simple as that one.

I had a similar problem as a child with hair clippers at the barber... some were really loud and were put right next to your ears!

if its bad for kids, imagine dogs.

I know the professional dryer my mother uses is specifically designed to put out good airflow but does so with by using a slower speed but larger vane fan. the motor and input is near the user with a long exhaust tube exiting near where the dog is, they are always mounted to allow ease of movement.

that sounds like a sensory processing issue.

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