Are noise-cancelling headphones making it harder for teenagers and young adults to understand speech in a noisy environment? That鈥檚 the provocative question聽: health reporter Hannah Karpel reports on five audiologists in the UK who are seeing an increase in young patients referred to them for hearing problems. The twist? Their ears are fine. The issue seems to be with how their brain processes sounds, and a hesitant finger is pointing at the noise-cancelling headphones they wear so much.
Skeptics often like to say that 鈥渢he plural of anecdote is not data鈥� to mean that anecdotes are unreliable, whether there is one or thirty-seven of them. But anecdotes聽are聽data: a low form of evidence, certainly, contaminated with all sorts of uncontrolled variables, but one that can serve as an early-warning system. Anecdotes can generate hypotheses that science can test properly.
These anecdotal reports by the BBC are certainly interesting but, for now, they lead to many unanswered questions, especially since the problem these young people are being diagnosed with is not without its share of controversy.
A microphone that creates silence聽
Headphones can cancel noise in one of two main ways. Just like the earmuffs used by people working in very loud environments, headphones can聽辫补蝉蝉颈惫别濒测听cancel out some noise by being thick enough and filled with sound-absorbing material like foam. No battery required; just a lot of stuff between your ears and the noises around you.
But a newer technology鈥攚hich became commercially available in聽鈥攃an cancel out noise聽补肠迟颈惫别濒测听through the use of a microphone. This tiny microphone can be placed inside the ear cup or outside of it, with some models using both. The microphone records the outside noise, like the loud hum of an airplane in the middle of your flight, and an internal circuit generates the same sound wave but inverted鈥攚ith negligible delay. Where the noisy sound wave goes up, the headphones鈥� sound wave goes down, and vice versa. They cancel each other out. This works especially well with constant, low-frequency hums, like those of a vehicle, fan, or air-conditioning unit.
More recent models of noise-cancelling headphones or earbuds can fade in ambient noise to give you some transparency on the go, and they can also adapt to how noisy the environment is and adjust the degree of noise cancellation in order to save battery life.
Some people鈥攁nd I include myself in this group鈥攅xperience a weird sort of pain while using noise-cancelling headphones. This is because the relative lack of low-frequency sounds reaching your ears is being perceived as a difference in pressure between your inner and outer ear. This is the same feeling we experience when on a plane that鈥檚 changing its altitude, and the sense of pressure inside our ears invites us to 鈥減op鈥� them: a strong swallow usually does the trick. But with these headphones, popping your ears won鈥檛 work because the problem isn鈥檛 the pressure. So the pain continues until we remove the headphones or turn off the noise cancellation.
None of this is worrying from a health perspective; but if noise-cancelling headphones make it harder for us to understand speech in everyday life, that would be concerning.
A cause or an effect?聽
The audiologists interviewed by the BBC are concerned by a rise in what is called auditory processing disorder or APD. It is also commonly called CAPD, where the 鈥淐鈥� stands for 鈥渃entral.鈥� To oversimplify, a hearing problem can be due to an issue with the ear itself (peripheral), but it can also arise further down the line (central), in the bundle of nerves linking your ear to the parts of your brain that interpret sounds, and in those brain areas as well. People with CAPD can usually hear just fine: when audiologists test their hearing, everything looks normal. But they have difficulty聽listening, which is to say that there is a processing problem along the way. Noise-cancelling headphones could be causing CAPD, although it is much too soon to know for sure.
When we look at the literature on CAPD, however, we find a lot of controversy. In a disputed聽聽that leans heavily into skepticism, Professor David R. Moore writes that he knows 鈥渙f no other area of audiology or neuroscience where such a long-standing intellectual, theoretical and practical impasse exists.鈥� The way to diagnose it is contentious; the interventions to treat it are not based in strong science; and it is firmly entangled with other disorders, like speech delays, dyslexia, and attention deficit hyperactivity disorder (ADHD), which can also be present in people with CAPD. Knowing how many people truly have CAPD is nearly impossible because its diagnosis is not as firmly set as it should be. Even ASHA, the American Speech-Language-Hearing Association, recognizes on聽聽that there is 鈥渙ngoing debate regarding how to define, assess, and treat鈥� this condition.
The ways in which CAPD manifests are tied to how sounds are refined, analyzed, organized, and interpreted by the brain. People with CAPD have difficulty understanding words in challenging environments: where there is noise, or reverb, or when the words are spoken quickly. They often ask people to repeat what they said. Children may have difficulty learning nursery rhymes or languages. They can also have difficulty paying attention. Clearly, there can be other explanations for these symptoms, like dyslexia or hearing loss, which is why CAPD is typically diagnosed by a multidisciplinary team using a battery of tests, none of which are considered a gold standard for the condition. But unlike ADHD, for example, people with CAPD will not see an improvement of their problem with medication, so there are ways to rule out other explanations.
I asked ASHA if they had noticed an increase in young Americans getting diagnosed with CAPD. They did not, at this time, have national data that would indicate an increase in consults for this condition. They put me in touch with Courtney Baker, an American audiologist, who pointed out to me that some people with CAPD will turn to noise-cancelling headphones to try to cope with their problem, to isolate the signal from the noise. In these cases, the headphones are a consequence of the auditory problem, not its cause.
Here, in Quebec, I spoke to Joanie Farmer, an audiologist and professional affairs advisor for聽, who told me over the phone that an increase in young people consulting for CAPD had not been reported to her and that she, as a practicing clinician, had not seen an uptick in these referrals. While the link put forth by the British audiologists has a certain logic, she said, it remains speculative.
Before we blame noise-cancelling headphones for a rash of hearing problems in the young, it鈥檚 important to also look at other explanations. The BBC coverage mentions a survey showing that nearly two-thirds of people aged 18 to 24 prefer to watch TV with the closed captioning on. They watch videos online with subtitles, we read, 鈥渄espite perfectly hearing the sound.鈥� This is a well-known problem that has nothing to do with noise cancellation.
Edward Vega did an excellent job covering it for聽.听Dialogue on TV and in films has been degrading over the years, and I don鈥檛 mean that screenwriters are incompetent. More microphones are used to capture dialogue during a shoot, which allows actors to leave behind the theatrical dialogue delivery of old and embrace a more naturalistic performance, mumbles and all. Sound that was garbled during shooting can theoretically be replaced in the editing room, by bringing the actor back in a studio, but this process costs money and studios are apparently using it less and less. And flatscreen televisions have tiny little speakers, often facing the back, which muddies the sound. No wonder we鈥檙e all reaching for the subtitles.
And there鈥檚 another reason many young people may be favouring closed captioning: actual hearing loss. Farmer told me that we are witnessing a rise in young adults presenting with a hearing impairment. Use of headphones and earbuds has skyrocketed and the volume is not always kept to a minimum, which means that many of us are losing our hearing at an earlier age than the previous generation. Hearing loss makes it difficult to hear dialogue on television, especially when viewing dubbed content where lip-reading is useless. Hence, subtitles.听
In the end, we are left at the beginning of a research process, not at the end of it. It鈥檚 possible that the overuse of noise-cancelling headphones鈥攂ecause they deprive our ears of noise鈥攚eakens the part of our nervous system that processes sounds. But this putative link has only been put forth by a handful of British audiologists at the moment: we need data from other countries. CAPD itself needs to be better researched, which will be hard as rehabilitative fields never get as much funding as, let鈥檚 say, cancer research.
There is also the possibility that any noise-cancellation-associated CAPD will be temporary. Farmer mentioned to me that people who had lived with hearing loss for a while before first getting hearing aids are warned: for a few days, maybe weeks, you will hear irritating noises you had forgotten existed. The scratches of a pencil on paper. The heavy footfall on the floor. Clicks, stomps, crinkles, and hums. Just like stepping out into a bright daylight makes it hard to see things at first, this noise will overwhelm. But the brain adapts and habituates. The same could be true for these young folks abusing their noise cancellation. We simply do not know.
For now, there is no need to toss out noise-cancelling headphones. In fact, they can be used to benefit people with CAPD as a sort of hearing aid, cancelling out some of the noise in transparency mode so the person can better focus on speech. Their use on public transportation can also allow for a reduced volume when listening to music or podcasts, thus protecting our ears from hearing loss.
滨迟鈥檚听overuse聽that we should be mindful of, at least until better data provides a sturdier sounding board.
Take-home message:
- A handful of UK audiologists are seeing an increase in young people having a specific hearing problem even though their ears are fine, and they are wondering if noise-cancelling headphones could be to blame
- The type of hearing problem seen is one that does not have a gold standard for diagnosis and which overlaps with other issues like dyslexia and ADHD
- Research is needed to look into this possible link, and while noise-cancelling headphones can be helpful to prevent ear damage during a commute, we should probably avoid overusing them
