This happens most often when they are not connected to a device or otherwise in use, and stop making noise when I connect a load to it such as by plugging in a device that is not fully charged.Is there anything I can do to suppress it? power-supply noise charger community-faq-proposedThese components use electromagnetism to convert AC mains power to low-voltage DC power. The internal switching frequency of an SMPS is typically low when unloaded and increases with load up to a certain point depending on the design. The no-load frequency is often low enough to be within the human hearing range. In addition, in low or no-load situations, the PWM used to regulate voltage at the inverter stage will be at a low duty cycle creating a "spikey" output profile which is more prone to causing vibration in coils, and the transformer itself will tend to vibrate as well (see Daniel R Hick's answer below for more details). Under load, a properly functioning SMPS should operate at a frequency well above the human hearing range, typically 50 kHz or higher (although some older designs operate at 33 kHz).

However, the same noise can occur under load with a poorly designed or defective power supply as the coils may vibrate under electrical stress at a subharmonic frequency. Coils used as inductors or transformers in other electronic devices, including those on motherboards, graphics cards, or other computer components, can also vibrate during operation. As such, a defective device can generate audible coil whine during operation. This is why you sometimes see weird gobs of glue on coils inside electronic devices. It is entirely possible for users to apply glue onto coils using a glue gun to suppress coil whine, and people have successfully done so on their computer parts. However, you generally can't do this easily on small wall chargers of the sort you mentioned without risking damage to the charger or exposure to potentially dangerous voltages. Ultimately, a whining noise isn't necessarily a sign of trouble in cheaper wall chargers when little or no power is being drawn from them.

However, a computer PSU or laptop charger that generates coil noise especially when under load may be defective and you may want to consider replacing it.buy split system air conditioner perth A "switching" power supply (like virtually all modern computer power supplies) works by "rectifying" the incoming 120V 60Hz (in the US) AC power into DC (at around 170 volts), "filtering" with capacitors, then using a semiconductor circuit to "chop" the DC voltage around 1000 times a second to turn it back into crude AC. (What's referred to as a "square wave"1000 cfm air handling unit, vs the "sine wave" of ordinary AC.) ac unit making buzzing soundThis "chopped" voltage then runs through a transformer to produce the desired output voltages.

The outputs are again rectified to DC and filtered, to produce the desired voltages for the computer. With this scheme, basic voltage regulation is performed by adjusting the "duty cycle" of the chopped voltage. When the power supply is lightly loaded the circuitry doesn't produce a nice symmetrical "square wave" but instead a series of narrow spikes, and that "spikey" waveform is more likely to produce annoying audible noise in the transformers and other components and is also more likely to produce "electrical noise" that you would, eg, hear in a nearby radio. Additionally, when a power supply is lightly loaded more of the magnetic field inside a transformer escapes to the case of the transformer and to surrounding components (since less is captured by the "secondary" coil of the transformer), and this "escaping" magnetic field is more apt to cause noise. The transformers are created in part by gluing plates of metal together. The AC fields causes back and forth forces in the metal plates.

As the transformer ages the plates begin to separate and allows for movement on the plates which vibrate causing the humming sound you hear. Is there anything I can do to suppress it? As they've already told you, glue, because glue adds damping to the vibrating coil, then the coil's stationary response gets smaller as well as the noise produced glue adds constraints to the coil, then the coil's (mechanical) fundamental frequency increases above your hearing capability. Another solution that wasn't mentioned (disclaimer: I haven't read ALL the comments...), and an environmental sound one! consists in unplugging the adapter (that's what I do all the time with the charger for my Nokia cellphone!) I came to this page as I bought a new Craftsman C3 19.2 V Li-ion battery / charger which started making that whining noise as I plugged in. I came up to look for some answer, while reading it, I realized I had one or two wireless charging toothbrushes (Philips Sonicare and an Oral B) next to it.

I moved the charger little away and the buzz went away. I presume the buzz is from electromagnetic interference from these wireless charging units that gets picked up by the transformers in the charger. The adapter of my router was also making a high-pitched noise which was literally driving me crazy. However, I solved this quickly by wrapping it up in a piece of cloth. Now I do not hear it anymore. You must log in to answer this question.Browse other questions tagged power-supply noise charger community-faq-proposed .Copyright © 1997 Hannabery HVAC. Noisy indoor unit, air handler, or furnace are all very common complaints in the HVAC field. But they usually fall into one of six different categories listed below. Some of these noises can also be caused by your air vents. For more information on this topic, click below... Loud scraping, metal hitting metal sound Loud thumping or vibrating noise Rattling, squealing or high-pitched sound Loud pop or bang sound

First of all, turn the system off immediately. This is usually the worst of the six different sounds. One cause for this sound is that the blower wheel came loose from the motor shaft, moved and is hitting the blower housing. In this case, if no damage was done to the wheel or the motor shaft, it could be moved back to the proper spot and re-tightened to the motor. Another and more likely cause is that the blower wheel actually broke, in which case it would need to be replaced. This makes a very disturbing sound almost as bad as fingernails on a chalk board. A third possibility is that a motor mount broke, causing the entire motor and blower assembly to drop and the blower wheel is hitting the housing. In any case, please shut off the system ASAP when this sound is heard or the repair bill could significantly increase. Sometimes this sounds like an out of balance washing machine. This is usually a blower wheel out of balance. Sometimes the motor itself can become out of balance as well.

The sound isn't usually too bad but shouldn't be ignored because it can cause other problems to the system. If the unit is working fine then most likely it is just a noisy transformer. Some transformers are louder than others and they all hum to some degree. If the unit is not working and a hum can be heard, it could be a bad indoor fan motor and/or capacitor. This applies mostly to Heat Pumps. This is usually refrigerant-flow related, such as a check valve, and it's not always a problem. Some units have noisy check valves or metering devices. If the sound gets louder or annoying and the air filter has been checked, then a service call should be placed. This usually happens when the system fan first starts and/or stops. This is also only found on systems with sheet metal ductwork, and it is usually from the return trunk. When the fan first starts the duct pops in from the negative pressure of the fan. When the fan shuts off, the pressure releases and the duct pops-out. This could be a sign of undersized duct, a clogged filter, closed vents or flimsy duct;

(For Gas or Oil-fired systems) Very Important: If you hear an unusual rumbling sound associated with combustion from your gas or oil-fired appliance, call for service immediately. This indicates what could be a serious problem with the burner portion of your appliance. Turn off equipment if necessary. Below is a list of possible causes. Items in red usually require a service call. Items in blue however can be addressed, some even fixed by the homeowner. Red = Professional fix | Blue = Homeowner fix Out of balance blower wheel Noisy refrigerant check valve Please keep in mind that the information found on our website is provided free of charge and Hannabery HVAC does not assume any liability resulting from the information we provide. We hope this information helps, but please note that these are just rough guidelines, and not all possible situations are covered. Your HVAC system should be inspected and repaired by a trained technician. [Must be in our service area]