“Safe” Noise Harms the Brain: The Hearing Journal

Helping clients navigate hearing in noise is an important part of an audiologist’s skill set, and noise-induced hearing loss is one of the most common causes of hearing impairment.

www.shutterstock.com. Noise, hearing, brain.

The National Institute for Occupational Safety and Health (NIOSH) specifies how long you can withstand exposure to a given intensity before hearing loss becomes a real risk. Sustained noises at a level of 85 decibels or more are damaging to the ears. Spending too much time in a noisy place, using power tools, or listening to loud music likely causes hearing loss. Many of us treat our own ears with respect by wearing hearing protection at concerts, while mowing, at the shooting range, or in other inevitably noisy places.

THE EFFECT OF THE COVID-19 PANDEMIC ON NOISE

But noise doesn’t have to be loud to cause biological damage, as my book, “Of Sound Mind” explains extensively. 1 When the human world temporarily went quiet during the first weeks of the coronavirus pandemic, people around the world noticed a distinct and refreshing lack of noise. Measurements from all continents have confirmed a reduction in man-made sound levels, in some cities of up to seven decibels.

The kind of noise that the pandemic has temporarily erased — the idling truck, the rumbling subway, the murmur of voices in restaurants, the noise of daily human activity — doesn’t damage our ears, and we can mostly ignore it. Yet, it should concern us for the sake of our brains. Having our hearing always “on” is taxing on the brain, especially when the noise is this brutal combination of unimportant and relentless. Our ability to distinguish signal from noise is crucial in almost everything we do, and the more noise surrounds us, the less able we are to call our brains to attention when attention is warranted.

INSIDE THE BRAIN

Our brains evolved to respond to otherwise predictable changes in sound patterns because our distant ancestors needed to be alerted to potential sources of danger. Separating signal from noise is evolutionarily important – think of the sudden movement of a snake while the crickets chirp. Chronic exposure to meaningless noise forces our brains to maintain an exhausting state of alertness and ultimately dulls our perceptions; the signal becomes more and more elusive. If you live in a noisy city or work in a noisy place, you may pass your audiogram but be less able to detect sounds in noise or pick up subtle timing cues in sounds than your peers who are used to quieter environments. You may be overly distracted by irrelevant sounds, compromising your work effectiveness, psychological health, and relationships.

A constant low-level barrage of meaningless sounds is especially devastating to a developing brain. Vital medical equipment in neonatal intensive care units has the unintended consequence of funneling a jumble of potentially damaging noises into the brains of fragile newborns during their developmentally critical first days, some scientists fear. . 2 This concern has spawned a rapidly growing field of study among neuroscientists and other specialists, suggesting that NICU auditory trauma may compromise infant linguistic and cognitive development.

Children raised in noisy neighborhoods often have a high level of neural noise in their brains, which means their auditory neurons are active even when the outside world is quiet. 3 The result is a noisy brain, processing sound less distinctly than it might otherwise. Another study found that chronic exposure to aircraft noise negatively affected cognition and reading comprehension in children. 4 Whatever the source of the noise, it erodes our ability to pick up the signal with sometimes devastating consequences.

THE IMPACT OF MAN-MADE NOISE ON NATURE

Human-made noise is also harmful to our non-human compatriots. During the weeks of lockdown in March and April 2020, many of us noticed a riot of birdsong. The birds increased the complexity of their songs, perhaps realizing that the hard work they put into their compositions would not be lost, buried under the usual human din. The birds also shifted the pitch of their songs down to fill the vacant lot space once filled with traffic noise. But here’s a little surprise about the birdsong during the quiet period: the birds have actually reduced the volume of their songs. Yet their quirky, sophisticated, and now softer songs went twice the distance and stood out with bold relief against the newly calm backdrop of our pandemic-induced commotion caesura. 5

Birdsong during a pandemic is just one example of human noise impacting animal life. Birds, frogs, and even whales, like humans, increase the volume of their voices as the environment becomes louder. Animals also change their call rates or pitches, or make other qualitative changes, just to be heard above us.

But sometimes animals just give up. Ship sonar can silence whales. It also interferes with the echolocation they depend on for navigation and is thought to be the cause of some strandings. 6 Man-made noise has forced hundreds of species of animals around the world to alter their behaviors, which has consequences for mating, migration and even their continued existence. As these species are doing, so can humans if the delicate balance between the human and animal worlds is upset more than it already has been.

Sound also has interesting and unexpected roles in plant life. Bran can stimulate plant growth and promote resistance to pests. 7 Some flowers release their pollen only when the preferred bee species buzzes with its characteristic tone. Evolution has “taught” tomatoes, peppers, eggplants, kiwis and other plants that the pollen from their flowers spreads best when carried on the bodies of species of bees that buzz at around 200-400 hertz. 8 Who knows how human-made noise might affect our non-animal cohabitants of the earth?

THE POWER OF SOUND

The power of sound is therefore ubiquitous but under-recognized. We rally around causes that reduce visual pollutants in our cities or protest the loss of forests, which are easy to see. But little is known about the acoustic network that helps many species thrive.

We’ve heard a little of what we’ve been missing in the spring of 2020. As man-made noise reaches its pre-pandemic roar, let’s not forget the damage we’re causing to our brains and to the other living beings we share this noise with. world.

THE REFERENCES

1. Kraus N 2021 Of Sound Mind: How Our Brain Builds a Meaningful Sound World, MIT Press.

2. Lahav A, Skoe E 2014 An acoustic gap between the NICU and the uterus: a potential risk of compromised neuroplasticity of the auditory system in preterm infants Frontiers in Neuroscience 8,381 https://dx.doi.org/10.3389%2Ffnins.2014.00381

3. Skoe E, Krizman J, Kraus N 2013 The impoverished brain: Disparities in maternal education affect neural response to sound Journal of Neuroscience 33 17221 17231 https://doi.org/10.1523/JNEUROSCI.2102-13.2013

4. Stansfeld S, Berglund B, Clark C, et al. 2005 Air and road traffic noise and children’s cognition and health: a cross-national study The Lancet 365 1942 1949 https://doi.org/10.1016/s0140-6736(05)66660-3

5. Derryberry E, Phillips J, Derryberry G, Blum M, Luther D 2020 Singing in a Silent Spring: Birds Respond to a Half-Century Reversal of the Soundscape During the COVID-19 Shutdown Science 370 575 579 https://doi.org/10.1126/science.abd5777

6. Simonis A, Brownell R Jr, Thayre B, et al. 2020 Co-occurrence of beaked whale and naval sonar strandings in the Mariana Islands, Western Pacific Proceedings of the Royal Society B: Biological Sciences 287 20200070 https://doi.org/10.1098/rspb.2020.0070

7. Creath K, Schwartz G 2004 Measuring the effects of music, noise and healing energy using a seed germination bioassay Journal of Alternative and Complementary Medicine 10 113 122 https://doi.org/10.1089/107555304322849039

8. Buchmann S Phillips S, Comus P, Dimmitt M 2015 Pollination in the Sonoran Desert Region A Natural History of the Sonoran Desert ■ University of California Press 124 129