Why does my phone make noise while charging wirelessly?
Wireless charging has become common feature in many latest smartphones. It offers a convenient way to charge your phone without plugging in wires. However, users often notice strange noises coming from their devices during wireless charging. While this noise is harmless, it can be annoying and disruptive.
This article has will explore what causes the noise during wireless charging, and provide solutions for limiting the sound while still using this technology.
How Wireless Charging Works
Wireless charging technology works by transmitting power between two objects through electromagnetic induction, which utilizes an electrical coil to create an alternating electromagnetic field between the two objects (the wireless charging pad and your phone). This is known as inductive charging.
The charging pad contains a transmitter coil, while your phone contains a receiver coil. An alternating electric current is passed through the transmitter coil in the charger, which induces an alternating magnetic field around that coil. When a device with an induction receiver coil is close enough to that magnetic field, a current is induced in that coil by the magnetic field. This thereby transfers power to your phone wirelessly to charge its battery, without the need for a physical wire or connector (Verizon, 2023).
Causes of Noise
There are two primary causes of noise in wireless chargers: coil vibration and electromagnetic interference.
Coil vibration is when the coils inside the wireless charger vibrate during power transfer with the phone’s coil, resulting in an audible buzzing or whining noise.[1](https://www.reddit.com/r/iphone/comments/82m72a/does_anyone_else_hear_a_high_pitched_noise_when/) This can be more noticeable in cheaper chargers that use lower quality components that are prone to vibrate.
Electromagnetic interference is when the high frequency signals from the charger interfere with other circuitry in the charger or phone, causing interference noises. The electrical current going through the charging coils creates electromagnetic fields that can induce noise into audio components if not shielded properly.
Coil Vibration
One cause of noise from wireless chargers is vibrations between metal coils inside the charger and phone. As explained, wireless chargers work using electromagnetic induction between transmitter and receiver coils. The changing magnetic fields induce currents and attractive/repulsive forces that can make the coils physically vibrate against each other at high frequencies.
These vibrations create audible noise and sometimes a high-pitched whining or screeching sound. The effect can be more noticeable with cheaper chargers that have looser tolerances or less structural rigidity to dampen vibrations. Using a high quality charger with tight construction may help minimize this noise.
Electromagnetic Interference
Electromagnetic interference (EMI) can cause the buzzing or whining noise you hear from your phone while it’s wirelessly charging.
When the power transfer coils in the wireless charger and phone resonate to exchange power, they also emit electromagnetic waves. These waves can interfere with other components in the phone, especially sensitive audio components like speakers.
The amount of interference depends on factors like how well shielded the coils are and how close together the coils are. More powerful wireless chargers with higher power transfer rates generally emit stronger electromagnetic fields and have a higher likelihood of interference.
According to Electronic Design, “EMI in Wireless Power Transfer Designs,” “Wireless power transfer (WPT) technology, an excellent technology for easier and safer battery charging, doesn’t use a wired electrical contact…”
Other Factors
The materials used in phone cases can also contribute to noise while wireless charging. Certain case materials like metal can interfere with wireless charging and produce noise. As noted on Reddit, “It’s called coil whine. Reason why is probably because you bought a cheap wireless charger.” [1] Using a high-quality charger made with better components can help reduce noise.
Additionally, the design and component quality of both the phone and the wireless charger impact noise levels. As explained on iPitaka, “And wireless chargers are no exception, they make noise as well. When your phone is on the wireless charger, an electromagnetic field is formed…” [2] Improved engineering and construction of both devices can mitigate unnecessary vibration and interference.
1. Phone Design
The design of the phone itself can contribute to noise while wirelessly charging. Some key factors include:
- Speaker placement: If the phone’s speaker is located near the wireless charging coil, the electromagnetic interference can cause the speaker to vibrate and make noise. This tends to happen more on cheaper phones with less internal shielding (source).
- Shielding: Insufficient electromagnetic shielding inside the phone allows interference to reach components like speakers and buzz or amplify the noise. High-end phones often have better shielding to prevent this (source).
So in summary, factors like cost-cutting speaker placement near charging coils and lack of shielding can lead more poorly designed phones to make noise when charging.
Solutions
There are a few solutions that can help reduce or eliminate the noise from wireless charging.
Charge Slowly
Charging your phone slowly on a low wattage wireless charger can help reduce noise. Slow charging applies less power, resulting in less coil vibration and electromagnetic interference (Should You Be Concerned If Your Wireless Charger Makes …, 2022).
Use a Case
Putting a case on your phone can dampen vibrations between the coils that lead to noise. A thick or rubbery case is ideal for reducing wireless charging noise by absorbing vibrations (Does Anyone Else Hear A High Pitched Noise When …, 2022).
Reposition the Phone
Noise can sometimes occur if the phone is not perfectly aligned on the charging pad. Repositioning the phone until the noise goes away can fix alignment issues between coils (Wireless Charger Making Wierd Noise (How to Fix) – Scan Techy, 2022).
Charger Design Improvements
Wireless charger manufacturers can implement some design changes to reduce or eliminate noise while charging.
Better shielding around the charging coil and electronics can block electromagnetic interference from radiating outwards. Shielding acts like a Faraday cage, containing the electromagnetic fields inside and preventing interference with the phone’s components.
Additional dampening or soundproofing materials added to the charger housing can absorb vibrations from coil movement. Soft padding placed under the charging coil can also dampen vibrations before they transfer into the surface the charger sits on.
Higher quality components such as capacitors, inductors, and transistors can produce smoother, more stable power output with less ripple or electromagnetic noise.
Some chargers even allow adjusting the charging frequency slightly, which can avoid frequencies that resonate with a particular phone’s hardware.
With quality engineering and testing, wireless chargers can transfer power efficiently and quietly to smartphones and other devices.
Conclusion
In summary, the noise heard during wireless charging is typically caused by electromagnetic interference between the coils in the phone and charger, as well as physical vibration of the coils. While harmless, it can be annoying to some users. Phone and charger manufacturers are continuously working to refine designs to minimize this interference and vibration. Advances in materials and coil layouts will likely lead to a quieter wireless charging experience in the future. With wireless charging adoption increasing, there is strong incentive for the industry to perfect the technology and provide a seamless user experience.
