Like seemingly everyone else I knew earlier this year, I was seduced into buying a pair of Apple’s Airpods bluetooth earbuds.
The UX (i.e. user experience) is pretty close to as amazing as advertised, so after finally acquiring a pair in May (they were sold out for months) I was using my Airpods nearly every day, often for hours on-end as I worked.
But after a few weeks of using them, I started to notice a concerning pattern.
Any time the Airpods were in my ears for more than an hour-or-so, I would notice myself feeling spacy, lacking-focus and a bit moody.
The longer the Airpods were in my ears, the more severe the effect.
Intuitively, my thoughts quickly went to the EMF (electromagnetic field) emitted by the Airpods (more on the biological effects of EMF exposure below).
But I’d used other (over-ear) bluetooth headphones in the past and never noticed anything undesirable, so given the relatively smaller size of the Airpods, they should be fine...right?
In retrospect, I’d clearly been been seduced into putting the “psychological blinders” on and ignored what should have been some red flags in the design of the Airpods. (specifically that, unlike over-ear headphones, Airpods sit literally INSIDE your skull)
Of course, I had to know if my subjective experience was supported by anything objectively measurable, so I bought an EMF meter and designed a protocol to test EMF’s generated by Apple’s Airpods vs other popular bluetooth and wired headphones.
Effects Of EMF’s On The Brain
In spite of the perception that EMF’s are a fringe new-age health topic, the effects of EMF’s on the body and brain have actually been quite well studied. Some quick searching on PubMed will yield literally thousands of studies investigating the impacts of EMF’s on various aspects of biological and psychological function.
Various types of EMF’s have been correlated with DNA damage, suppressed immune function, increased incidence of cancer, decreased fertility, and autism (just to name a few).
The spectrum of EMF’s is actually quite broad and a lot of these aren’t relevant to this informal study. For example, radio-frequency EMF’s (RF-EMF’s) emitted by cell phones have been particularly well studied and are correlated with some of the most troubling health effects, but aren’t emitted by headphones in levels significant enough to consider here.
(For a thorough overview of the research on EMF’s, the Bioinitiative Report is a good resource.)
For this article, I’ve focused on the specific type of EMF most intensely emitted by bluetooth headphones, referred to as low-frequency EMF’s (LF-EMF’s).
There are many hundreds of studies showing the effects of LF-EMF’s on hormone function, cellular metabolism, DNA transcription and other elements of body health.
To keep the information here as relevant as possible to this informal study, I’ll focus only on research showing the effects on the brain by the LF-EMF’s specifically measured by the EMF meter:
- Several studies have shown LF-EMF’s to alter the function of the neurotransmitter nitric oxide and associated enzymes in the brains of mice. 
A 2014 study showed that exposure to LF-EMF’s increased NMDA receptor activity, leading to an increase in anxiety behaviors in mice. 
- Several studies have shown LF-EMF’s to disrupt transport of essential nutrients and neurotransmitter-precursors (i.e. choline) into and throughout the brain. 
- LF-EMF’s have been shown to reduce levels of the antioxidant enzymes catalase, superoxide dismutase and glutathione reductase in the brain. (These enzymes are the brain’s primary mechanism for protecting itself from oxidative damage.) 
- LF-EMF exposure leads to altered levels of monoamine neurotransmitters (norepinephrine, serotonin and dopamine are just a few) in mouse brains. 
- A 2013 study showed LF-EMF’s to have a “devastating effect” on memory consolidation in male and female mice. 
A 2015 study used fMRI to look at patterns of brain activation in humans exposed to LF-EMF’s. “Significant changes” in functional brain activation were observed. 
Analysis: Apple AirPods
1. High Average Intensity
The average EMF intensity produced by the Airpods was easily the highest of all the headphones tested, likely by several times over the next-closest headphone (probably B&O H9...it would be difficult to do true calculations of averages because of the way the meter displays data, so we’ll have to go with the eye-test).
2. Consistent Field Intensity
The thing that stood out to me most with the AirPods was how consistently the reading stayed in the 7-10 milligauss (mG) range.
Every other headphone produced an EMF that varied in intensity quite a bit, largely corresponding to changes in the input audio as far as I could tell.
I assume this consistent intensity is due to the bluetooth technology Airpods use to communicate with the devices they are paired to. (That seamless, consistent, long-distance pairing comes at a cost, apparently)
I see this consistency as potential concern in-and-of itself. Quite a few studies done on LF-EMF’s showed that different field intensities exert qualitatively different effects on brain chemistry (rather than just quantitatively different).
More consistent exposure to a narrow intensity-range would mean greater magnitude of a certain type of neurohormone disruption.
This is in contrast to headphones that generate EMFs more variable in intensity - the expected effect in this case would be more types of neurohormonal disruptions, but all in lower magnitude of effect.
Does narrow intensity range translate to a more significant disruption to cognition and mood? It’s hard to say without research, but it could be an explanation for why I noticed disruption to mood and cognition with Airpods and not other bluetooth headphones.
3. Proximity To The Brain
Last but not least, Airpods sit, quite literally, inside the skull. If you were looking for the ideal place to sit an EMF-generating device to exert maximum effect on the brain, the ear canal would be a pretty good choice.
One look at a map of the primo-vascular (i.e. meridian) system of our ears tells you how connected our ear canals are to our nervous system (and thus, our brain).
Whereas in over-ear bluetooth headphones, the bluetooth transmitter sits at least 1cm away from the ear (thus distributing the EMF over a much larger area of ear and skull) - the bluetooth receiver in Airpods essentially makes direct contact with the nervous system only a couple centimeters from the brain itself.
Analysis: Other Bluetooth Headphones
At test volume, the Bose headphones stayed fairly consistently in the 1-5 mG range, with an average field intensity somewhere around 2.5 mG.
The B&O headphones generated a slightly stronger field, also largely in the 1-5 mG range, but with an average intensity closer to 3.5 mG.
Again, it’s important to note that in contrast to Airpods, the bluetooth receiver in both of these over-ear headphones sits at least 2cm away from the ear/skull, thus distributing the field over a larger surface area.
Analysis: Wired Headphones
If the goal is reducing EMF exposure over all else, wired in-ear buds are the clear choice.
The only over-ear wired headphones tested, Audio Technica ATH-M50x had easily the highest variance in field intensity at test volume, jumping from 1-10 quite erratically. The average intensity was likely somewhere in the 2-3 mG range.
The field generated by wired headphones comes almost entirely from the drivers themselves (speakers are magnets!).
The M50x’s have the largest drivers in the test by a good margin, so it makes sense the field generated would vary in intensity in sync with the input audio.
Limitations Of The Informal Study
There is are some important differences between the methods used to study EMF's in the academic studies and wearing headphones.
To start, the intensity of the electromagnetic field used for the academic studies is several times greater than what headphones produce. As a counterpoint to this, the EMF’s in the majority of the studies were generated by antennas in the room with the subjects, and not a device making direct contact with the skin (as with Airpods).
The intensity of an EMF decreases with distance, so having a device sitting in the ear is going to exert a much more intense effect on the brain than the same device sitting a few feet away.
Does this proximity to the brain compensate for the lesser intensity of the field? Probably not totally, but it’s fair to expect the effect exerted on the brain by the EMF’s to be more similar than the intensity figures alone would suggest.
Along the same lines, distance of the headphones from the measurement device will also have an effect on the measurements produced. I positioned the headphones relative to the EMF meter in such an orientation as to produce what I thought were the most consistent and accurate readings across all devices. Ear buds and over-ear headphones are very different shapes and sizes, so data here is not going to be perfect.
I also tried to keep in-ear volume as consistent as possible across all headphones. Setting the Macbook to volume-level 7, for example, will produce very different in-ear volumes in different headphones, so this required a bit of extra human-ear calibration. Not perfect, but I believe I got levels pretty close across all headphones.
The Headphones I Use Post-Test
The convenience of bluetooth headphones would be hard to give up entirely, so this test was embarked upon in-part to find “the best” bluetooth headphones using both conventional criteria (sound quality, UX, comfort, etc) and my own brain-performance-optimization criteria (EMF’s).
The Bose QC35’s were the clear winner here for me. The comfort and sound quality are excellent, and the intensity of the EMF was lower than any other bluetooth headphone tested.
Plus, the noise cancelling is clearly a step above the B&O’s, which lends an additional brain-enhancing effect in that it reduces stress levels as well as the amount of energy your brain has to use to subconsciously to filter background noise .
I do also use my B&O H3 in-ear with some frequency. I love the way these sound, they’re quite a bit more portable, and sometimes it’s simply too hot to wear ear muffs (i.e. over-ear headphones).