# I can "Hear" when electronics are on? **URL:** \ **Category:** Factual Questions\ **Created:** [November 9, 2009, 4:15am UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879 "2009-11-09T04:15:34Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [November 10, 2009, 8:42pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/21 "2009-11-10T20:42:30Z")
There is a curious phenomenon where certain individuals can hear electronic power supplies that are totally silent to most other people; this usually occurs in tinnitus sufferers where the ultrasonic emissions from the equipment meets the tinnitus noise, and due to the non-linearity of the ears amplitude response this produces intermodulation distortion products that are lower in frequency, and hence audible to that one person alone. Not a special power I’d like to have, I think. ---
**Author:** ![Cliffy](https://avatars.discourse-cdn.com/v4/letter/c/59ef9b/32.png) [@Cliffy](https://boards.straightdope.com/u/Cliffy)\ **Post date:** [November 11, 2009, 4:38pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/22 "2009-11-11T16:38:54Z")
I too can hear electronics hum, although I guess probably more when I was younger. It was quite convenient when I was a boy. My computer was in the basement, so if I was worried I’d left it on, I could just open the basement door instead of traipsing all the way downstairs to check. –Cliffy ---
**Author:** ![salinqmind](https://avatars.discourse-cdn.com/v4/letter/s/3ec8ea/32.png) [@salinqmind](https://boards.straightdope.com/u/salinqmind)\ **Post date:** [November 11, 2009, 4:43pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/23 "2009-11-11T16:43:01Z")
In spite of a lifetime of having my ears blasted with loud music, I can hear (thankfully) when electric appliances (coffee maker, oven, stove) are on, not doing anything, but are switched on. ---
**Author:** ![YourAdHere](https://avatars.discourse-cdn.com/v4/letter/y/65b543/32.png) [@YourAdHere](https://boards.straightdope.com/u/YourAdHere)\ **Post date:** [November 13, 2009, 7:10pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/24 "2009-11-13T19:10:01Z")
There is a certain high pitched noise that certain electronics like a tv and the flash on a disposable camera make which older adults typically can no longer hear. I thought it was so neat when I discovered that high school kids use this as a ringtone on their cellphones since older teachers will not be able to hear it. It’s like some sort of dog whistle for teenagers. Unfortunately for them I’m 25 and I can still hear it, and my sister is 30 and she can still hear it as well. ---
**Author:** ![BACI](https://avatars.discourse-cdn.com/v4/letter/b/ce73a5/32.png) [@BACI](https://boards.straightdope.com/u/BACI)\ **Post date:** [November 13, 2009, 10:40pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/25 "2009-11-13T22:40:36Z")
There’s no doubt that on the occasions when a blackout has hit my house, and there’s no electricity even coming into the property, the stillness is significantly more profound than when I’m awake in the middle of the night with everything electrical nominally turned off. I find it disconcerting. I don’t know how you’d describe the sound of a digital bedside clock but it has a presence that goes missing when the power is cut. ---
**Author:** ![\_RavensFlight](https://avatars.discourse-cdn.com/v4/letter/_/e9a140/32.png) [@\_RavensFlight](https://boards.straightdope.com/u/_RavensFlight)\ **Post date:** [October 4, 2016, 10:54am UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/26 "2016-10-04T10:54:23Z")
I can always hear it too and it makes having electronics in the room annoting and painful because I have extra senative hearing ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [October 4, 2016, 1:33pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/27 "2016-10-04T13:33:14Z")
I have an Acme Mk 3 zombie detector that emits a low hum when it detects a zombie. ---
**Author:** ![JcWoman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jcwoman/32/2889_2.png) [@JcWoman](https://boards.straightdope.com/u/JcWoman)\ **Post date:** [October 4, 2016, 1:33pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/28 "2016-10-04T13:33:39Z")
> [@BACI](#): > > There’s no doubt that on the occasions when a blackout has hit my house, and there’s no electricity even coming into the property, the stillness is significantly more profound than when I’m awake in the middle of the night with everything electrical nominally turned off. I find it disconcerting. I don’t know how you’d describe the sound of a digital bedside clock but it has a presence that goes missing when the power is cut. I have noticed this also. I like to think of it in emotional terms as the house being “dead”. (Temporarily, I hope.) Similarly, I can always hear (unless I’m busily/actively ignoring the “house heartbeat hums”) our sump pump running under the floor of our basement even when I’m on the ground floor. Our basement is wonderfully dry but I’ve been told that the water level is just inches below the floor, so having the sump cycling on and off all the time is a normal and happy sound. If we ever get heavy rains and I don’t hear the sump running then I know there’s trouble around the bend. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [October 4, 2016, 1:39pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/29 "2016-10-04T13:39:36Z")
> [@Morgenstern](#): > > I have an Acme Mk 3 zombie detector that emits a low hum when it detects a zombie. Hmmm? ---
**Author:** ![iceiso](https://avatars.discourse-cdn.com/v4/letter/i/3be4f8/32.png) [@iceiso](https://boards.straightdope.com/u/iceiso)\ **Post date:** [October 4, 2016, 2:14pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/30 "2016-10-04T14:14:28Z")
Yes, so timely! I had a similar conversation with my fiance just a few days ago. I used to be able to “sense” that a TV was left on in a house, even if it was muted, and before entering through the front door. As described earlier, it was a pressure I could feel behind my eyeballs. Something else that drives me crazy is when people scratch their metal utensils against ceramic/metal dinnerware. I’ll get dizzy/nauseous and most definitely lose my appetite. Others usually can’t hear it and when they can, it has no effect on them. Does anyone else have a heightened sensitivity to this? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [October 4, 2016, 3:58pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/31 "2016-10-04T15:58:59Z")
Interesting thread, so those voices aren’t in my head then? ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [October 4, 2016, 7:08pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/32 "2016-10-04T19:08:51Z")
> [@Musicat](#): > > Hmmm? More of an Ummmmmmmmmmmmmmmmmmmmmmmmm ---
**Author:** ![guitario](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@guitario](https://boards.straightdope.com/u/guitario)\ **Post date:** [October 4, 2016, 8:11pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/33 "2016-10-04T20:11:46Z")
Isn’t this a normal thing? I recall being in school around the age of 9 when I was talking to a teacher at the end of the day… most of the kids had left the classroom and although it was ‘quiet’, someone turned the computer off at the wall, and the sensation was that it was ‘quieter’ but nothing other than a feeling. Like others have said, things give off a hum, and we pick up on a lot of noise or frequency that our conscious mind may not pay attention to, but when it’s not there, it becomes slightly noticeable. ---
**Author:** ![Kimballkid](https://avatars.discourse-cdn.com/v4/letter/k/b5a626/32.png) [@Kimballkid](https://boards.straightdope.com/u/Kimballkid)\ **Post date:** [October 4, 2016, 8:37pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/34 "2016-10-04T20:37:07Z")
> [@Morgenstern](#): > > I have an Acme Mk 3 zombie detector that emits a low hum when it detects a zombie. > [@Musicat](#): > > Hmmm? > [@Morgenstern](#): > > More of an Ummmmmmmmmmmmmmmmmmmmmmmmm Wouldn’t it be more of a Braaaaaains? ---
**Author:** ![TwiSpark](https://avatars.discourse-cdn.com/v4/letter/t/77aa72/32.png) [@TwiSpark](https://boards.straightdope.com/u/TwiSpark)\ **Post date:** [October 4, 2016, 8:41pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/35 "2016-10-04T20:41:56Z")
I get that very slightly, I think, though always assumed it was my imagination from ‘expecting’ things to be on. But far more noticable were CRTs (never see them now) which were nothing short of noisy to me as a child. Most annoying to me now is coil noise - which unfortunately affects many PC PSUs, graphics cards, laptops, cheap USB chargers, and allegedly the iPhone 7 (not sure, that might be something else, I’ve not seen/heard one). That’s like a high pitched hissing/fizzing sound and gives me a headache if it’s a bad one. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [October 5, 2016, 12:56pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/36 "2016-10-05T12:56:40Z")
> [@BACI](#): > > There’s no doubt that on the occasions when a blackout has hit my house, and there’s no electricity even coming into the property, the stillness is significantly more profound than when I’m awake in the middle of the night with everything electrical nominally turned off. I find it disconcerting. I don’t know how you’d describe the sound of a digital bedside clock but it has a presence that goes missing when the power is cut. The challenge would be to be able to accurate say if the power is on or off, in a blind experiment… that is, you are in a room with no electric devices turned on - and you can’t hear a tv or radio playing its station or white noise or that sort of thing… You can’t be exactly on the otherwise of a wall to the refrigerator … you are five metres from any refridgerator freezer and that sort of thing. Central heating/air con unit has to be off because like, it hums big time. ---
**Author:** ![Mavic\_Chen](https://avatars.discourse-cdn.com/v4/letter/m/e56c9b/32.png) [@Mavic\_Chen](https://boards.straightdope.com/u/Mavic_Chen)\ **Post date:** [October 5, 2016, 2:21pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/37 "2016-10-05T14:21:09Z")
Zombie thread I know, but I just wanted to chime in. I find that a lot of wall chargers for phones etc give off a distinctive hissing-type buzz when they have no load. When charging they are silent but once the device is charged the circuit changes and the hissing commences…! ---
**Author:** ![Fridgemagnet](https://avatars.discourse-cdn.com/v4/letter/f/22d042/32.png) [@Fridgemagnet](https://boards.straightdope.com/u/Fridgemagnet)\ **Post date:** [October 6, 2016, 5:17pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/38 "2016-10-06T17:17:42Z")
> [@Mavic\_Chen](#): > > Zombie thread I know, but I just wanted to chime in. I find that a lot of wall chargers for phones etc give off a distinctive hissing-type buzz when they have no load. When charging they are silent but once the device is charged the circuit changes and the hissing commences…! There’s an explanation for this: When your switched mode power supply is running into a moderate to full load then the voltage (or current if it’s a current output) is regulated by altering the width of the pulses in the output pulse train; a narrower pulse means less output voltage/current, and vice-versa. However, under very light loads the system reaches a point where it can’t make the pulses any narrower due to various technical limitations. To avoid an overvoltage/overcurrent condition the regulator has no choice but to start missing out pulses. Some systems miss out the odd pulse or two here and there, which is known as Pulse Skipping. Other systems employ a series of pulse bursts, which is a short train of pulses followed by a significant pulse-free gap - this is known as Burst Mode. If a continuous train of pulses has frequency components above the human audio range then it’s generally inaudible (though some people have special powers and can pick this up), but as soon as pulses are being skipped then the frequency spectrum can intrude into the audio range. Normally it’s an inductor or transformer that produces the sound due to magneto-restriction, but cheap ceramic capacitors (i.e. almost every ceramic cap that isn’t a C0G dielectric) also make good little transducers due to the piezoelectric effect. I am wary of switched mode power supplies that make hissing/spitting noises, as it’s generally indicative of a poorly tuned control loop. A well designed supply might sing a little, and that’s OK, but hissing and spitting means that there’s a large degree of chaos in the pulse skipping due to the control loop not being very stable. ---
**Author:** ![Hypno-Toad](https://avatars.discourse-cdn.com/v4/letter/h/b2d939/32.png) [@Hypno-Toad](https://boards.straightdope.com/u/Hypno-Toad)\ **Post date:** [October 6, 2016, 5:23pm UTC](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879/39 "2016-10-06T17:23:25Z")
I always remembered that “ultrasonic” sound when a TV was turned on. Started as a burst that then rose out of my perception. Sort of like it got quieter as it rose, but not really. [Previous page](https://boards.straightdope.com/t/i-can-hear-when-electronics-are-on/516879.md?page=1)