Expired

Whistling electric plugs ?

20
Found 3rd Oct 2014
I can hear my phone charger whistling when switched on ? I can also hear other electrical items whistle sometimes.
I've read that electric items do this and just depends on how good your hearing is at that frequency. or the items are faulty or the electric current is dirty ?
Just curious if any electricians/ electronic types know for sure ?

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Common noise problem samsung chargers...I'm guessing you're using a samsung phone?
You can hear at higher frequency usually the younger you are some people have more sensitive hearing may also hear these's tone's
Some electrical's do produce a high frequency sound i'am in my 30s i can hear an alarm unit at work whilst other can't.

I'am not 100% on how this sound is produced from all appliances but i would be guessing if i said the sound in some came from within the electronic circuits from inductors and ceramic capacitors.

The cross product of current and magnetic field is a force. Forces always work on two things, which in the case of a inductor are the core and individual segments of wire that make up the windings. At the right frequency, this can make the winding vibrate a bit, which you hear as sound.

Edited by: "savage27" 3rd Oct 2014
Can't answer the question but yeh I hear my phone charger doing the same.
my Samsung does this too very annoying!
bruce287 not a Samsung charger but I might get a new one just in case.
savage27 sounds like what you said. Have to charge it on other side of room it seems
northeastkev it appears to be a common inconvenience then :-(
PS the gear 4 is quite loud whistling in standby but my gf can't hear a thing !
Check out Mains Hum
Denbi

bruce287 not a Samsung charger but I might get a new one just in … bruce287 not a Samsung charger but I might get a new one just in case.savage27 sounds like what you said. Have to charge it on other side of room it seems northeastkev it appears to be a common inconvenience then :-(PS the gear 4 is quite loud whistling in standby but my gf can't hear a thing !



I am the same yet my hubby who is older doesn't hear the noises. I have BlackBerry charger but we also have Samsung and nokia one.
It is very annoying and only does it when the phone is fully charged or plug not in use and not turned off.
kester76

Check out Mains Hum


It's not mains hum - that's the frequency the grid runs at.

The high-pitched whistle comes from the switched-mode power supply which uses a higher frequency to be more efficient. Usually it's too high to hear but not always.
nick1austin

It's not mains hum - that's the frequency the grid runs at.The … It's not mains hum - that's the frequency the grid runs at.The high-pitched whistle comes from the switched-mode power supply which uses a higher frequency to be more efficient. Usually it's too high to hear but not always.


It's the transformer/coils that causes the issue. You don't get switch mode PSU's in basic phone chargers.
See en.wikipedia.org/wik…ise
The whine is vibration. If it wasn't then it wouldn't move the air to make the noise.

3 Phase invertors are damn loud to the point you can hear the thing screaming at certain frequencies but they're not common at home luckly.
http://www.digyourowngrave.com/content/matrix_vision.jpg

Sounds like a form of 'the one' syndrome best see a doctor
Some plugs do it, some other devices too. I think itt's when the electric is trapped in the capacitors. Usually heard most on standby. I hear it too from my PSU and my external harddrive power plug.
It's not mains "hum" that's 50Hz, and it' not "trapped" electric either. What's happening is normal and will be different for each design,here's a rough explanation of what's going on -

Basically Mains AC power is first stepped down to a lower voltage (a bit above the output voltage), then converted to DC (rectified) with a diode bridge. Here's where the interesting part happens- a special regulator circuit rapidly switches the power on and off. The capacitor smooths this out, creating a constant voltage. This output voltage is continuously sampled by the switching regulator so it knows if the capacitor needs more 'on' or 'off' time.

Think of it like a 10PSI water hose, connected with a T-junction to a balloon, and you want 5PSI output. So you constantly watch the output pressure guage and turn the water on when it hits 4.9PSI and off when it hits 5.1PSI. The balloon will absorb these pulses of pressure and result in a steady 5PSI output.

Now this switching circuit works fast- in the kilohertz range. Most switching power supplies use a switching frequency above 20-30KHz so the human ear can never hear it. However for one that is in the 10-20KHz range, the switching is sometimes translated into audio frequency noise by aging capacitors.

The noise changes based on how much power is being consumed by your phone. When the phone is consuming power, the switch is 'on' more often. When the phone uses less or no power (unplugged), the switch (even if it operates at a supersonic frequency) may only be 'on' one out of every several hundred cycles, which creates an audible tone in the capacitor.

Hope this makes sense ?
Edited by: "RxTx" 3rd Oct 2014
It's the transformer or a coil acting like a transformer resonating due to magnetic flux like savage27 quoted.
There is no oscillation in dc it's zero Hz unless you have ac ripple which is smoothed out my the capacitors.
kester76

It's the transformer or a coil acting like a transformer resonating due … It's the transformer or a coil acting like a transformer resonating due to magnetic flux like savage27 quoted.There is no oscillation in dc it's zero Hz unless you have ac ripple which is smoothed out my the capacitors.



It's not mains hum as savage27 said, it's switching of the output by the PSU to stabilise the output at the correct DC voltage. There is a small transformer in the output and it is this vibrating at the switching frequencies that is what we hear.
RxTx

It's not mains hum as savage27 said, it's switching of the output by the … It's not mains hum as savage27 said, it's switching of the output by the PSU to stabilise the output at the correct DC voltage. There is a small transformer in the output and it is this vibrating at the switching frequencies that is what we hear.



Yep hands up you're right. I assumed wrongly that usb chargers worked on the same principle of as the old DC chargers I learnt about in the past. I checked out nolenf.wordpress.com/201…er/ and it explained that the practice of using a transformer/bridge rectifier/smoothing capacitor/zener diode or 7805 was too wasteful of electricity so they swapped to more efficient design.

Also explains why my nettop worked during a brown out but my wife's old led clock radio didn't.


Hi kester76,

The newer types of PSU have lots of advantages over the old ones, as you said they are much more efficient, generate less heat as well and are much lighter because they don't use the traditional type of transformer to step down the mains voltage. Another key advantage is that the way the switch mode ones work allows them to accept a very large range of input voltages, which means your ipad PSU just needs the connector swapping when you go to the USA for instance. The PSU chops up the incomeing 110V in the USA in the same way as it does the 230V in the UK, it doesn't make a jot of difference as far as it's concerned and means that Apple etc can manufacture one PSU that works anywhere in the world.
Here's a write-up on wikipedia that does a much better job of explaing how they work than I did - Switched Mode Power Supply
Edited by: "RxTx" 3rd Oct 2014
RxTx

Here's a write-up on wikipedia that does a much better job of explaing … Here's a write-up on wikipedia that does a much better job of explaing how they work than I did - Switched Mode Power Supply


Thanks for the link. I remember most of it from college, the inverter part was described as a mark space ratio or Pulse width modulation but this was back in 1996 I think. I've only seen full bridge block diagrams but never heard of a 'Ringing Choke Converter' but checking brings up that it was patented late 1998. Seems weird only having a single diode to half wave rectify but it cuts down on interference.
Ok thanks for the input everybody. We've had quite a few suggestions from knowledgeable people but i think the correct answer must go to RxTx. From what you have said people arnt generally supposed to hear this noise but ageing capacitors may be part of the problem.
Its not a sign of dodgy electrics or appliances and there's not much i can do about it other than try a different charger hoping that it vibrates at a lower frequency i cant hear. Many Thanks.
Edited by: "Denbi" 4th Oct 2014
My nexus charger does it, i switched the the usb plug bit with my old apple one and it no longer does it. Im really sensative to this kind of noice. Old Tvs, plugs humming, drives me crazy
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