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Can you hear ultrasonics?
September 29, 2005 12:35 AM   Subscribe

does anyone else hear ultrasonics? (high pitched sounds generally considered outside the range of the human ear) on a thread yesterday, some MeFites said they did, and i always thought it was just me.

ever since i've been a kid, i've heard these high-pitched sounds that no one else seemed able to hear. most notably, TVs left on with no signal, but also computers, radios, various other bits of electronics. on the thread linked above, fivefreshfish, loquacious, and a few others pointed out that they regularly hear these sounds as well, and i'm fascinated by it, since i haven't encountered anyone who had experience with this. is this a common thing?
posted by spiderwire to Technology (50 answers total) 2 users marked this as a favorite
 
When I was a child, I could hear them so loudly that older TVs would cause me to leave the room. I've since done a bit of damage to my ears by spending too much time in nightclubs, but I can still hear it, faintly.

However, the upper limit to your range of hearing degrades significantly as you age, so you won't have to worry about it for too much longer.
posted by Jairus at 12:43 AM on September 29, 2005


It's relatively common. I can hear TVs and some dimmer lights that aren't turned all the way up. It's not a special ability, our hearing just stops at a higher point - and it's definitely fading out up at that level, I can just hear one of those dog chaser but I'm sure it's deafening for a dog. Which makes me wonder just how loud our appliances are up at those frequencies (and if so why aren't all dogs traumatized and slightly deaf).
posted by abcde at 12:47 AM on September 29, 2005


I used to until I destroyed my upper range hearing through loud rock shows. I'd have to turn off monitors all the time around me, because if the computer wasn't on the ringing would drive me nuts.
posted by angry modem at 1:08 AM on September 29, 2005


I'm not sure I would call these things ultrasound, because the very definition of ultrasound is sound of a frequency too high for a human to hear... and you're hearing it. The high pitch of a TV is approx 15.7kHz, which is far below the often-spouted "20kHz ceiling." I would guess that most of these things that people tend to notice are still under 20kHz, but I don't doubt there are some rare people that can hear far past that. There have been studies of this and I'm sure someone has a link.
posted by Rhomboid at 1:12 AM on September 29, 2005


I used to. Loud music and/or age destroyed the ability some time in my mid twenties. Now the only high pitched whine I hear is my tinnitus.

I can still pick the noise of a flyback coil about to go. There's a race on between when all the old CRTs get decommissioned and the last short haired sensors in my ears die.
posted by i_am_joe's_spleen at 1:13 AM on September 29, 2005


I can hear dodgy CRTs and roo-scarers (like a dog whistle but very high-powered with a chirp noise and bolted to the front of some cars/trucks in AU). Can't say I've ever heard a door-sensor thing as mentioned by a poster in the previous thread - all the ones I've seen are optical.
posted by polyglot at 1:45 AM on September 29, 2005


I hear bats.
posted by altolinguistic at 3:23 AM on September 29, 2005


Another ultra-oral-sonic-er here. Older/dodgy TVs, failing PSUs and burglar alarms etc. all annoy the hell out of me.

I mentioned it to my doctor in passing a while ago and he said that the ability to hear very high frequencies inaudible to most people is often a side-effect of asthma (which I have). Is there any correlation here?
posted by NeonSurge at 3:27 AM on September 29, 2005


i want to hear everyone's age. i'm in my mid-twenties, and i'm just now thinking that i might have recently lost the ability to hear these ranges, because i can't remember the whine of the TV bugging me recently.

then again, i haven't had a TV for 5 years for precisely this reason, so it's hard to say. :)

there are still a lot of odd super-high-pitched noises that disturb me, though, like the sound of a camera flash charging. abcde brought up the dimmer lights -- it'd forgotten that one, but it's definitely been aggravating at times. any idea what causes those sounds?; why powered-down appliances seem to make weird high-pitched whines? (any engineers in the audience?)

and joe's spleen, is it really about the "short hairs" in your ear canal?

i'm hoping that loquacious happens upon this thread -- he's a DJ and claims to still be able to hear in this upper range, which is what made me start to wonder if we all lose this ability later in life, and why. "too much loud music" seems to convenient to me since i'm not the concert-going type. i mean, it could be like the need for reading glasses that we all seem to develop as we age, despite still having good vision -- but i'm still waiting for the link that explains it all.

my google skills failed me at this one. either way, in this case it sounds like a mixed blessing -- that whine annoys the hell out of me, but i'm something of an amateur audiophile and i dread the thought of losing that faculty as i age. but it seems like a lot of middle-aged audiophiles get along just fine without. is it a learned skill?

(this is something i'm all of a sudden super-curious about -- like i said, it was always a mystery to me as a kid. so if anyone's reading this an chuckling at my ignorance, please excuse my naivete.)

regardless, good to know i'm not the only one, though, so thanks all. ...esp. Rhombold for the note about TV frequencies -- i don't suppose you have a link for that?
posted by spiderwire at 3:30 AM on September 29, 2005


NeonSurge, no breathing problems here. did he give a reason? that sounds weird to me.

Rhomboid, dictionary.com says that "ultrasonic" is "Of or relating to acoustic frequencies above the range audible to the human ear, or above approximately 20,000 hertz," so i think we're both right here -- either way, we're talking about things that some of us can hear and others can't, and that's what i was wondering about. i didn't know that other people were hearing this stuff, too.


[also... this is kind of (actually, extremely) tangential, but after surfing around from the killer green beret assassin dolphins thread recently i came upon an interesting chapter from a book by john c lilly (note: the guy's a quack -- a "pathetically eager acid freak," as HST would put it, if that's offputting to you) about the acoustic abilities of dolphins... the good stuff us about a third of the way down the page. amazing to think about what those creatures can do. can't imagine how they would feel about TVs...]
posted by spiderwire at 3:41 AM on September 29, 2005


When I sat my hearing test for the Royal Signals I scored stupidly high on the tests for different ranges. You sit in an anechoic chamber and press a little button when the tone is played to indicate that you can hear the noise. I do have to admit that scoring 100% was easy since all you had to do is listen to when the white noise between the tones ended.

Otherwise, count me as one of the people that can hear all these annoying noises such as tv tubes etc.
posted by longbaugh at 3:48 AM on September 29, 2005


I, too, can hear common high-pitched noises like televisions (small ones in particular), dimmer switches, and stuff, though I believe all of this stuff is approximately within the 20 kHz range. I believe age has a lot to do with it, though, as my parents are cheerfully oblivious to these sounds.

I mentioned it to my doctor in passing a while ago and he said that the ability to hear very high frequencies inaudible to most people is often a side-effect of asthma (which I have). Is there any correlation here?

Now that's fascinating. I wonder why that would be the case.
posted by musicinmybrain at 4:10 AM on September 29, 2005


If you're curious how high 20 Khz really is, you can generate sine waves of various frequencies with TrueRTA. Very high frequencies may be unreliable, as your speakers may not be able to handle them and may produce lower frequencies... also, it may or may not be possible to produce very high frequencies at volumes which are damaging to your speakers if you really try. However, try 16000 Hz with an amplitude of -9 or so. That's roughly the pitch of a television's whine (no, I don't have a link; I state this from personal experience).
posted by musicinmybrain at 4:28 AM on September 29, 2005


More discussion of this here.

I hear those TV-left-on noises and I also hear [or feel] a lot of very low-level sounds that those around me don't even notice like trucks idling in the parking lot. When I worked in a large office with a noise-music fan I suddenly felt this really distressing sort of vibrating hum, low and very disorienting. I wandered around the office trying to track down where it was coming from and it was this guy, trying out some very low frequency noise generator thing. Apparently I was the only one who heard it. I'm 37 and I have asthma, if that matters.
posted by jessamyn at 5:08 AM on September 29, 2005


Bats and tv monitors drive me nuts. Once a roommate had a graphic EQ that caused me searing physical pain in my throat(?) when he set it some way, yet he heard nothing.
posted by dong_resin at 5:56 AM on September 29, 2005


My fiance says he can hear the high pitched noises TVs make. In the same vein, he is also very sensitive to the high pitched squeals little kids tend to make.

I mentioned it to my doctor in passing a while ago and he said that the ability to hear very high frequencies inaudible to most people is often a side-effect of asthma (which I have). Is there any correlation here?

Oddly enough, my fiance does have asthma.
posted by geeky at 6:01 AM on September 29, 2005


I'm 27 and I can definitely hear when a TV is on anywhere in our (small) apartment. I noticed this when I was a kid. In science class the teacher played a record of sounds at different frequencies to demonstrate hearing ranges. After a little bit, I was the only one who could still distinguish the sounds. Two years of raving doesn't seem to have affected this, although I certainly hear the "buzz" when there are no other noises.
posted by Who_Am_I at 6:13 AM on September 29, 2005


I can still, despite rock-and-roll and gunfire, hear a tv set or a bat fluttering by. Like Jairus, as a kid I'd have to leave the room when certain TV's turned on. My brother was the same way.

By the way if you can hear these sounds, don't even think about getting one of those devices that uses sound waves to keep bugs and pests away!
posted by Pollomacho at 6:31 AM on September 29, 2005


Like spiderwire, I've always found the whine of camera flashes charging to be the worst. Certain TVs and monitors are a close second, though, and sometimes I could swear I've heard something near the doors of big stores. [Door sensors? The anti-theft thingies? I'm not sure.] I've become better at subconciously tuning it out - I currently have to keep my computer in my bedroom, for example, and so unless I think about it [like now] the noise from that particular computer and monitors doesn't bother me. I seem to have exercise-induced asthma, by the way, though it's never been officially diagnosed. Not sure what the connection would be...
posted by ubersturm at 6:43 AM on September 29, 2005


Oh good. Count me in too. Add to the list some types of flourescent lights, in stores and classrooms, and I've even discovered a couple of those emergency lights putting out a horrendous noise that no one else seemed to hear. I knew I was in trouble when I started sympathizing with my cat about things in our house... tvs, etc. I'm 27 and have EIA.
posted by jwells at 6:47 AM on September 29, 2005


I hear bats, flourescent lights, and CRTs.
posted by odinsdream at 6:56 AM on September 29, 2005


and joe's spleen, is it really about the "short hairs" in your ear canal?

I'm far from an expert on the subject, but your "short hairs" do have something to do with your hearing. I only know this because My high school physics teacher left his research post where his lab tried to regrow the hairs because normally they don't really grow back.
posted by jmd82 at 6:59 AM on September 29, 2005


I've always been able to hear bats chittering really clearly so I was amazed when someone tried to tell me their calls were outside the normal range of human hearing.
posted by Decani at 7:03 AM on September 29, 2005


I too can hear those high-pitched tones emitted by TVs, some lights, and other electronics. However, the severity of it has lessened. Either I've just learned to tune it out or the years of rock-music abuse on my ears has reduced their sensitivity.

OR (here's where it gets interesting)

Like many asthmatics, I've been slowly outgrowing it and haven't really felt its effects in several years. Perhaps, my ability to hear those appliance frequencies is diminishing in proportion to suffering from asthma.
posted by Jon-o at 7:04 AM on September 29, 2005


NeonSurge: I have asthma but have yet to receive any superpowers that may be due to me.
posted by mullacc at 7:08 AM on September 29, 2005


Just curious, what does asthma have to do with it?
posted by Pollomacho at 7:26 AM on September 29, 2005


Nevermind, reread that sentence.
posted by Pollomacho at 7:27 AM on September 29, 2005


As I mentioned in a previous thread, I can hear this awful ultrasonic pest repeller at my mom's house... I have to unplug it everytime I visit.
posted by amro at 7:33 AM on September 29, 2005


I should also say, all those other things you've mentioned drive me nuts, too... And I don't have asthma and I'm (sigh) 29, almost 30...
posted by amro at 7:34 AM on September 29, 2005


I also do not have asthma or allergies. I'm 22.
posted by odinsdream at 7:44 AM on September 29, 2005


I can hear flourescents, bats, dog whistles, bad motors, you name it.

Funny thing is that I'm 80% deaf in my left ear and 30% in my right since I was a baby. I can't hear any lower tones at all, but ultrasonics? Loud and piercing clear. I don't think that I'm deaf so much as just having a shifted spectrum.
posted by zerokey at 8:01 AM on September 29, 2005


No asthma, 36, and this hasn't diminished over the years. While on jury duty I had to get the court maintence crew to replace a bad thermostat. It was screaming so loudly at such a high pitch only i could hear it.
posted by Classic Diner at 8:24 AM on September 29, 2005


I'm 25, asthmatic, and can hear all those things. I'd forgotten about dimmer switches because I haven't been around them since my grandma died; her house was the only place I knew that had them. Oddly, I realize now that because of that fact, I have a positive emotional reaction to that sound (which is lower-pitched, to me, than the TV sound), because it means grandma's house.
posted by librarina at 8:41 AM on September 29, 2005


22, no asthma, I hear tvs buzzing, camera flashes charging, and buzzing dimmer switches, which for me sound low pitched not high pitched compared to tvs.

This ability has died away in recent times - probably a cause of too much loud music in clubs and gigs (the brits have different laws on how loud our clubs and gigs can get, from the sound geeks I know we have it several decibals louder)
posted by 13twelve at 8:49 AM on September 29, 2005


I can hear into a pretty high range, too: [list of things whatnotever can hear]. I'm 24ish, no asthma. I do have constant, mild tinnitus, though. At a self-administered test in a (noisy) museum I could hear up to about 19kHz.

One thing those of you with the ability might check out some day is computers. Open one up and get your head close enough, and you can actually hear it "computing." Different loads/tasks produce distinctly different whines and hisses. For example, compare idle vs dragging a window around the screen. And I'm not talking about sound-card interference; this is from the actual electronics vibrating. It's kinda neat to hear.
posted by whatnotever at 8:50 AM on September 29, 2005


I can hear all these things too, and I can't tell you how relieved I am to see this thread. When I was about 9 I went on a field trip to some science museum where they played high pitched sounds at us. We were supposed to raise our hands at the beginning and then take them down when we stopped hearing the sound. I could still hear it and was the only child with her arm still in the air, and the docent or teacher or whoever was giving the demonstration told me I was lying, that noone could hear ultrasonic sounds. I've never forgotten it and suddenly I feel justified. FWIW I'm 42 and I still hear bats & TVs & all the other noises, but not quite as clearly or as often as I used to. I've never had asthma.
posted by mygothlaundry at 8:52 AM on September 29, 2005


Add me to the list who can. 28 and never had asthma FWIW. I too am glad to see I'm not the only who can hear the high pitched noise from TV tubes and the like.
posted by johannes at 9:14 AM on September 29, 2005


I don't think my doctor (or I) meant that asthma is the only cause of high-frequency sensitivity, just that asthmatics are more likely to have this sensitivity. From personal experience and some of this replies in this thread, this seems to be correct. I've no idea what the connection is... any medical types out there care to offer an explaination?
posted by NeonSurge at 9:27 AM on September 29, 2005


I have always "perceived" some kind of highpitched whine every single time I have gone into any Sears...if I stay too long I get a headache. I have noticed this since childhood (in the 60's) and no other department stores have this effect on me. Weird.
posted by konolia at 9:38 AM on September 29, 2005


I'm 22, asthmatic, and can hear all this stuff. I learned early on not to comment on it, because everyone thought I was going crazy! Good to know that it's only because I'm the only asthmatic in the family.
posted by chota at 9:56 AM on September 29, 2005


I hear this stuff too, and I have asthma. 25 years old.
posted by agregoli at 10:15 AM on September 29, 2005


I have to unplug my laptop every night, because when it's connected to the power source the whine keeps me awake. And I can't stand florescent lights. No asthma.
posted by cali at 10:58 AM on September 29, 2005


One more to the "I hear stuff" list. 26, non-asthmatic, and like many other people, I'm relieved someone actually asked this question.
posted by wanderingmind at 11:15 AM on September 29, 2005


Ultrasonic = beyond the human hearing range. Anyone who tells you they can hear them is mistaken, but probably just misidentifying sounds that are actually well below 20kHz.

So lets say you are in a room that contains ultrasonic energy. This energy might still cause the tiny bones in your ear to vibrate, but there's an organ behind these bones called the cochlea that is responsible for turning that mechanical vibration into signals that the brain understands. The cochlea is filled with fluid and is lined with thousand of tiny hairlike cilia, each of which is attached to a nerve that is connected to the parts of the brain responsible for "decoding" sound.

When a sound wave hits the eadrum, it vibrates the three bones of the inner ear, which in turn cause pressure waves in the fluid that travel down the spirals of the cochlea. The nature of the pressure wave, which is dependent upon the frequency of the initial sound, determines which cilia it excites. And it is an excited cilia that causes us to say "I hear something."

So the reason a person with normal hearing cannot hear frequencies above about 20kHz isn't that the brain doesn't care to pass that information along in a recognizable fashion, it's that those frequencies don't excite any cilia and thus don't generate any brain signals whatoever.

Here's a description of the workings of the ear in more detail


Anyone who can, verifiably, hear ultrasonics is a mutant or some other freak of nature.
posted by pmbuko at 11:53 AM on September 29, 2005


30, and boy howdy, dimmers drive me nuts.
posted by unixrat at 12:22 PM on September 29, 2005


I'm 35, and had asthma as a child. And when I talked about short hairs, I was thinking of the cilia. I don't really know squat about the detail of how ears work, so much thinks pmbuko.
posted by i_am_joe's_spleen at 12:35 PM on September 29, 2005


pmbuko's link makes me think that it must be the outer end of the basilar membrane being more or less flexible that determines the top end of your range - corrections welcome.
posted by i_am_joe's_spleen at 12:37 PM on September 29, 2005


I also hear this stuff. My hearing was tested in a radio broadcasting class in high school, and I basically tested as a freak of nature. :) Since then I have heard (and played) a LOT of loud music but I haven't destroyed my high-range hearing yet, as testing just a couple of years ago revealed. I'm 40 now, and yes, asthmatic.

There is some evidence that I may have a Central Auditory Processing Disorder, and that supposedly tends to come along with above-average hearing (but poor auditory processing). The result is, though I can hear dimmer lights, tv whines, and all kinds of irritating noises, I have to say "what? huh?" all the time when people talk to me.
posted by litlnemo at 1:56 PM on September 29, 2005


there are still a lot of odd super-high-pitched noises that disturb me, though, like the sound of a camera flash charging. abcde brought up the dimmer lights -- it'd forgotten that one, but it's definitely been aggravating at times. any idea what causes those sounds?; why powered-down appliances seem to make weird high-pitched whines? (any engineers in the audience?)
The reason those things are driving you crazy is because they are all electronics that use a general class of design loosly called "switch mode". You might have heard of a "switch mode power supply", which is the kind used in computers -- as distinct from the simple "power bricks".

So in a camera flash, a capacitor must first be charged to several hundred volts so that it can be rapidly discharged into the xenon flash tube causing the burst of light. But most flashes are only powered by a simple battery that produces a handful of volts (varies depending on type and number of batteries.)

In order to charge that capacitor, a circuit called a dc-dc converter is used; this is a type of switch mode power supply. In essence, the low voltage DC output of the battery is switched on and off rapidly to create an AC signal that is fed to a transformer. The ratio of windings in the transformer causes the voltage to be increased by the desired amount, and the output is rectified and fed to this high voltage capacitor, resulting in the needed charge. The reason it is done this way is because a transformer can only work with AC, so the DC output from the battery must be fed into this oscillator.

The particular frequency required is determined by the physical properties of the transformer, but in most cases it's in the general ballpark of tens of kHz. You are probably familiar with the very well-known "whine" of a flash charging up after being discharged -- it's kind of a rising pitch that gets higher and queiter. This is because these charging circuits often vary the frequency of the oscillator as a cheap way of regulating the output. As the capacitor gets closer and closer to being charged to its target voltage, the oscillation frequency will get higher and higher, which results in the vary familiar whine. This type of circuit that varies the frequency like this is often used because it can be implemented very cheaply with few parts.

Why such high frequencies? For a given power requirement, you can generally make a transformer much smaller and lighter if it can be used with high frequencies. That is why your flash camera has a tiny little transformer that weighs almost nothing, wall the everyday "wall wart" transformers that you plug into your household outlet (50Hz or 60Hz depending on where you live) weigh a ton and are huge.

So we have this electrical oscillator circuit that is powering this transformer at (say) 15kHz. That is obviously the source of the whine that some people are sensitive to, but why do you hear it when it's just an electrical signal? The answer is magnetostriction which is a fancy way of saying, "a transformer will sometimes vibrate at the same frequency as the electrical signal passing through it." Obviously this is an undesired property of a transformer, which should otherwise be completely silent, so it's a design goal to minimize this as much as possible. And indeed most transformers are effectively silent, but old age or poor quality control can cause them to really start to squeel.

This general concept of a high frequency transformer making a whine is probably the common cause behind most all of the annoyances listed in this thread. It explains the television, computer monitor, camera flash, computer power supply, and just about any other electronic device that uses a switch-mode power supply.

The light dimmer has a similar reason, but it does not involve a transformer. But it is still an example of a switch mode circuit. The job of a light dimmer is to reduce the amount of power that would otherwise flow to the light bulb. The simplest way to do this is just by adding resistance, but the problem is that this dissipates power. If a dimmer switch was just a resistor, it would get hot and probably melt. Light bulbs dissipate large amounts of power and there is no practical way to control their brightness with a resistive load.

So, instead the dimmer uses a switch that opens and closes rapidly to regulate the power that gets to the light bulb. Conceptually you can think of someone standing at the light switch, turning it on for one second and then off for one second. The overall light output will be half since the light is only on for half of the time. But once every second would be very noticeable and annoying, so these things usually work with the natural 60Hz frequency of the power line. Visualize one cycle of a sine wave: the dimmer will allow current to flow for part of the cycle, but then turn it off prematurely. The timing of when in the cycle the swich opens and closes determines the amount of power that flows to the light, and thus its brightness.

But this is happening at 60Hz, so where does the high pitched whine come from? The answer (I believe) is because of the nature of this switching. A pure 60Hz sine wave has only a single frequency component at 60Hz. But if you start chopping this wave, you generate harmonics at multiples (octaves) of this fundamental frequency. The degree to which this happens is closely related to how abruptly you do this switching. Unfortunately, from the standpoint of dimmer design, you need this switching to be as instantaneous as possible, because the short time period where the switch transitions between open and close causes enormous power dissipation inside the switch (which is a piece of silicon, usually called a thyristor or SCR.)

So these abrubt on and off transitions cause there to be high frequency harmonics. The details of why this is the case requires a fair amount of mathematical background in the fourier series, and isn't really important.

I am also not sure of how this gets acoustically coupled, since there are usually no transformers involved in a dimmer, but I assume it's just a variation of magnetostriction. The AC signal flowing through the switch (and everything else in the circuit, including the wiring, socket, and light bulb itself) causes vibrations that the sensitive ones of you are able to hear.
posted by Rhomboid at 5:26 PM on September 29, 2005 [1 favorite]


Great post Rhomboid.

Often the frequency of operation of a switch mode power supply is highly temperature dependant. As the frequency of operation comes close to the mechanical resonant frequency of the materials in a magnetic component the noise will start.

I have a computer power supply that is really whiney when you turn it on, but it quiets down if I have enough stuff plugged into it. On the other hand I have worked on power supplies that only start to whine when you load them very heavily.
posted by Chuckles at 7:33 AM on November 30, 2005


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