It’s more common than you think. Folks with better-than-average hearing will tell you that a lot of phone chargers and other USB power supplies will give off some sort of noise when they are in use. This is sometimes characterized as a crackle, a hiss, a hum, or a high-pitched squeal. In rare cases it may sound like a recurring “wee-wee-wee-wee” noise. You might have noticed something like this. Not everyone can hear it, and other folks may be convinced it’s in your head. Trust me, it isn’t.
Why does this happen at all?
Considering that there are no moving parts in a phone charger, you might ask yourself how it’s even possible for a charger to make noise. The answer is simple, and it’s all part of how a phone charger works.
Current comes into the charger as 110 volts, alternating current. This is the standard for power in the US and throughout North America. Your phone, on the other hand, needs 5 volts, direct current. The whole purpose of the charger is to convert from one to the other.
(Now the difference between alternating and direct current is a subject for a whole different article, but it’s probably enough to point out that batteries charge on direct current, and alternating current is needed for long power lines. I’m simplifying things a bit but that’s the basics of it.)
Take away the plug, USB connector, and plastic shell, and you’re mostly left with two things on the inside of a phone charger. There’s a transformer, which steps the voltage down to what the device needs. There’s also a rectifier, which turns AC current into DC current. Aside from a few other bits, that’s all there is.
How the sound happens
Because alternating current comes in at 60 Hertz (60 cycles per second), it can set up vibrations inside the transformer as the current alternates. There can be similar things happening in the rectifier. The result can be a hissing, squeaking, squealing, or something sounding like a belt slipping. It may not make sense that parts that don’t move can create these noises, but they can because the energy itself is moving.
Different people can interpret the sound differently because there are usually vibrations at different frequencies. Older folks are more likely to hear a hissing, or something like a carbonation fizz, while younger folks are more likely to hear the squeal.
Generally, chargers have some sort of goo or tape in them to help minimize vibration. Over time these vibration dampeners get less effective. So you’re likely to have this problem on older chargers rather than new ones. Also, large laptop power bricks are less likely to have this problem because there’s more room for vibration dampening material.
Is this a problem? Is it even safe?
Generally, a sound coming from a charger is not a safety issue. If you’re hearing more of a crackle, that could represent a problem but most likely does not. It does generally mean the charger is getting old or that it wasn’t really well built in the first place.
If your charger is giving you trouble of any sort, especially if the noise is bothering you, you should replace it. You’ll find a lot of great phone accessories when you shop at Solid Signal, including both wired and wireless chargers.
