If you’ve ever wondered how your headphones or earbuds work, you’ve likely researched and learned that they have magnets in their design that help to convert audio signals into sound.
Are the magnets in headphones/earbuds bad for you? There are no studies to suggest that the magnets and the relatively small magnetic fields in headphones have any negative effects on your brain, ears, and/or body. However, the sound levels produced as a result of these magnets may cause hearing damage if driven too high.
In this short article, we’ll discuss the effects of magnetic fields on humans and the safety measures we should take when wearing headphones and earbuds.
Before we begin, I should state that I am not a medical professional nor am I a scientist that studies and experiments with magnetic fields. Rather, I am an audio engineer and blogger. Much of the information in this article has been sourced from professionals that know much more than I do in the fields of human health and magnetic fields. The sources are listed at the end of this article.
How Do Magnetic Fields Affect Humans?
Let’s start off by stating that the Earth itself is like a giant magnet. A spinning ball of liquid iron in our planet’s core produces a huge magnetic field with a north pole and a south pole.
Humans have evolved with the Earth and so we’ve evolved to survive and thrive in magnetic fields. Furthermore, our very own nervous systems produce electromagnetic fields.
To add to the everyday magnetic fields that surround us, humans have created artificial magnetic fields with power lines, electrical appliances, and many other commonplace technologies. In fact, due to electromagnetism, any flow of electrical current has a coinciding magnetic field.
The magnitude of the Earth’s magnetic field at its surface ranges from 25 to 65 microteslas and is considered static at a single point, meaning it is not varying rapidly at any given point (including at a human body).
The tesla is an SI unit for magnetic flux density with base units kg/(s2•A)
The Earth’s natural magnetic field does cause any harm and its effects are practically omnipresent.
Stronger magnetic fields, like those produced by magnetic resonance imaging (MRI) machines (in the 0.5 – 3.0 Tesla range) can trigger nausea, dizziness and a metallic taste in the mouth, but these effects are temporary.
The negative effects of the electromagnetic fields generated by our household devices, including headphones, are minimal.
That said, the WHO (World Health Organization) suggest the upper limit of continuous exposure for the general public be 40 mT.
As far as we know, there’s no solid evidence to suggest that the magnets in headphones are harmful or harmless to humans. There are barely any regulations on the matter and it is not a commonly discussed issue.
Wireless headphones and their effects on the brain, however, has become more of a conversation and argument since Bluetooth headphones exploded in popularity in the 2010s.
Why Do Headphones Have Magnets?
The vast majority of headphones use magnets in their drivers. Headphone drivers are the transducer elements that effectively convert audio signals (electrical energy) into sound waves (mechanical wave energy).
These drivers are referred to as dynamic drivers and utilize the principle of electromagnetic induction to move a diaphragm and produce sound waves that represent the applied audio.
An overwhelming percentage of headphone drivers are designed with the moving-coil dynamic driver design (the same design used in most loudspeakers, monitors and subwoofers, and in some microphones). Though planar magnetic and balanced armature headphone drivers also have magnets and work on electromagnetic induction.
Let’s quickly go over how the most common moving-coil headphone driver design utilizes magnets. We’ll start by having a look at a simplified cross-sectional diagram:
The audio signal is passed through the voice coil which is attached to a movable diaphragm and suspended in a cutaway of an oddly-shaped permanent magnet. This audio signal is an alternating current and, thereby, induces a varying magnetic field in and around the voice coil.
This induced magnetic field interacts with the permanent magnetic field, repelling and attracting the coil in such a way that moves the coil (and the diaphragm) back and forth within the cylindrical cutaway.
The strange magnet design in the driver concentrates its magnetic flux lines through the coil for maximal effect. That is why the north pole is placed directly to the interior of the coil and the south pole is placed directly to the exterior. There is minimal space between the coil and the magnetic structure to further improve efficiency.
For more detailed information on dynamic headphones and the relationship between headphone drivers and magnets, check out the following My New Microphone articles:
• What Are Dynamic Headphones And How Do They Work?
• Why & How Do Headphones Use Magnets?
How Strong Are The Magnetic Fields In Headphones?
The magnetic field strength of headphone magnets varies greatly from model to model.
Though many headphones have magnetic field strengths that would typically have a noticeable effect on our physiology, they really do not affect us much. The fields are concentrated and typically lose most of their strength before they reach our brains.
It’s important to note that the magnetic field of a headphone driver’s permanent magnets is static and will have much less of an impact as a time-varying magnetic field of the same strength. The electromagnetic field produced by the moving-coil/diaphragm is time-varying but practically negligible relative to the permanent magnet.
I’ve assembled a shortlist of headphones/earphones and their rated magnetic field strengths at their drivers:
|Headphones Model||Magnetic Field Strength (At The Driver)||Headphones/Earphones|
|JVC HA-FX33A||1.10 mT||Earphones|
|Philips SBC HS430||7.90 mT||On-Ear Headphones|
|Apple Earbuds||19.6 mT||Earphones|
|Philips SHE5920||21.5 mT||Earphones|
|Bose QuietComfort 25||24.0 mT||Over-Ear Headphones|
|JVC HA-F130A||25.2 mT||Earphones|
|Sony MDR-E828LP||26.0 mT||Earphones|
|Beats By Dre (original)||26.7 mT||Over-Ear Headphones|
|Sony MDR-Q22LP||34.4 mT||On-Ear Headphones|
|Beyerdynamic T1||1200 mT||Over-Ear Headphones|
|AKG K812||1500 mT||Over-Ear Headphones|
|AKG K872||1500 mT||Over-Ear Headphones|
Shure ensures that all their earphones have field strengths of less than one millitesla (<1000 microtesla) with the measurement meter as close as possible to the earphone driver.
As we’ve discussed, static magnetic fields of 0.5 Telsa in MRI machines cause ill effects and the WHO’s guidelines say we shouldn’t expose ourselves to more than 40 milliTesla for an extended period of time.
So then, by that metric, the 1.5 Tesla magnetic field of the above-listed AKG K812 should certainly have adverse effects on our brains and physiology. What makes them safe, then?
AKG is featured in My New Microphone’s Top 13 Best Headphone Brands In The World.
Well, the magnetic field of the oddly-shaped headphone drivers are very concentrated. Additionally, these magnetic field strengths are measured at the magnet of the headphone drivers. There is a significant decrease in field strength as we distance the measuring point from the magnet.
With all that being said, headphones have been in use for decades and there is no solid evidence that their magnetic fields cause harm to our physiology. This, to me, is evidence (or lack thereof) enough to make me feel safe wearing my headphones.
The volume of the headphones on/in our ears is much more concerning, which brings me to my next point.
The Potential Of Hearing Damage When Wearing Headphones
Although the magnets within headphones are extremely unlikely to cause any noticeable effects on our physiology due to their magnetic fields, headphones and earbuds do pose a threat to our health. This has to do with our sense of hearing and the potential damage high sound pressure levels may cause.
The sound pressure level of a sound wave, like the strength of a magnetic field, drops as a function of distance. The further the sound travels, the less intensity and power it carries with it.
Sound pressure level decreases according to the inverse-square law which states that for every doubling of distance, the SPL is quartered. In other words, for every doubling of distance, the SPL drops by 6 dB.
For this reason, earphones will be more damaging than headphones at any given sound pressure level. The drivers of earphones are positioned inside the ear canal while the drivers of headphones are positioned outside the ear. This seemingly small difference in driver placement makes a huge difference in the intensity of the sound pressure at our eardrums.
We could, of course, just turn up the volume on our headphones and get to the same level at the eardrum, but I digress.
Hearing damage occurs when we are subjected to very high sound pressure levels. A shotgun firing or a firecracker going off right next to your head, for example, would cause hearing damage.
However, hearing damage can also happen at lower levels over extended periods of time.
Below is a table that describes the recommended maximum time limits for continued exposure to various sound pressure levels.
To the left of the table is the NIOSH Standard (National Institute for Occupational Safety and Health) and to the right of the table is the OSHA Standard (Occupational Safety and Health Administration).
NIOSH is a United States federal agency while the OSHA is an agency of the United States Department of Labor. Both offer their own guidelines as to the amount of time we can safely listen to varying sound pressure level intensities.
Note that the SPL ratings are given in dBA (A-weighted decibels) which represent perceived loudness rather absolute pressure (as dB SPL does). This is because our hearing is naturally less sensitive at the lower and higher ends of the audible frequency range. At 1 kHz, dBA and dB SPL match.
Note, too, that hearing damage is often frequency-specific. For example, hearing hammering at a loud resonant frequency over time is likely to damage that part of our hearing range.
Without further ado, here is the table:
|NIOSH Standard (dBA)||Equivalent Sound Pressure Level (at 1 kHz)||Maximum Exposure Time Limit||OSHA Standard (dBA)||Equivalent Sound Pressure Level (at 1 kHz)|
|127 dBA||127 dB SPL|
|1 second||160 dBA||160 dB SPL
|124 dBA||124 dB SPL|
|3 seconds||155 dBA||155 dB SPL
|121 dBA||121 dB SPL|
|7 seconds||150 dBA||150 dB SPL
|118 dBA||118 dB SPL|
|14 seconds||145 dBA||145 dB SPL
|115 dBA||115 dB SPL|
|28 seconds||140 dBA||140 dB SPL
|112 dBA||112 dB SPL|
|56 seconds||135 dBA||135 dB SPL
|109 dBA||109 dB SPL|
|1 minute 52 seconds||130 dBA||130 dB SPL
|106 dBA||106 dB SPL|
|3 minutes 45 seconds||125 dBA||125 dB SPL
|103 dBA||103 dB SPL|
|7 minutes 30 seconds||120 dBA||120 dB SPL
|100 dBA||100 dB SPL|
|15 minutes||115 dBA||115 dB SPL
|97 dBA||97 dB SPL|
|30 minutes||110 dBA||110 dB SPL
|94 dBA||94 dB SPL|
|1 hour||105 dBA||105 dB SPL
|91 dBA||91 dB SPL|
|2 hours||100 dBA||100 dB SPL
|88 dBA||88 dB SPL|
|4 hours||95 dBA||95 dB SPL
|85 dBA||85 dB SPL|
|8 hours||90 dBA||90 dB SPL
|82 dBA||82 dB SPL|
|16 hours||85 dBA||85 dB SPL
To be safe, I’d recommend following the NIOSH standard to keep levels low and reduce the risk of hearing loss.
The moral: keeping your headphones at a reasonable level and taking regular breaks will increase the longevity of your hearing; reduce ear fatigue, and improve the quality of your listening experiences now and in the future.
How do wireless headphones/earbuds work? Wireless headphones work with radio frequencies or infrared signals. A transmitter encodes the audio signal into an RF or IR signal and emits it wirelessly. The receiver, built into the headphones, accepts the RF or IR signal, decodes it back into the audio signal and sends it to the HP driver.
Why do headphones need power? Most headphones have passive transducer elements (drivers) that convert audio to sound via electromagnetic induction. However, there are electrostatic headphone drivers that do require power to function. Additional features such as active noise-cancellation, built-in amplifiers and wireless systems also require power.
For more information on headphones and their power requirements, check out my article How Do Headphones Get Power & Why Do They Need Power?