Marina Sarris

Date Revised: December 14, 2023

Donald was “perfectly petrified of the vacuum cleaner.” So was Elaine, who would not venture near the closet where her family’s vacuum was stored. Richard, Barbara, and Virginia, on the other hand, ignored sound to the point that others wondered if they could hear at all.¹

They were among autism’s first children,² described in the landmark 1943 article by Leo Kanner that gave a name and description to a condition that today affects 1 in 36 children in the United States. Kanner, an American psychiatrist, advocated for a new diagnosis for these children, some of whom had been assumed to have intellectual disability.

Among other things, most of the children he saw shared an unusual relationship to sound – either ignoring or fearing it. Seventy years later, in 2013, American psychiatrists officially recognized under- or over-reacting to one’s senses as one of several signs of autism.

The senses include sight, touch, taste, smell, and movement. But for many people, the most recognizable sensory sign of autism involves hearing. Children on the autism spectrum are often shown covering their ears to block out noise. In fact, that’s what Elaine did when she heard the rumble of the vacuum cleaner. She was hyper(over)-responsive to noise. Richard, Barbara, and Virginia were hypo(under)-responsive; they barely acknowledged many sounds.

Researchers still have many questions about how children and adults on the autism spectrum process information from their senses, and how it affects development.

Noise sensitivity is common in autism, although it also occurs in people who don’t have autism. At one point in their lives, 50 to 70 percent of autistic people were hypersensitive to everyday sounds, according to a 2021 scientific review.³ This may cause distress and interfere with routine activities, such as sitting in a noisy classroom or traveling to work amid rumbling trucks and blaring horns.

Some participants in SPARK, the largest study of autism, have described different perceptions of, and responses to, sound. Some report being very sensitive to sounds of certain intensity, pitch, and tone, or feeling bombarded by noises that other people tune out. Others are not bothered by loud sounds and have even played in a band. No one single type of sensory symptom is “consistently associated” with autism.⁴

How is Sensory Information Typically Processed?

Think of your brain and nervous system as a controller, taking in information from your senses, deciding what’s important, and choosing how to react. If you don’t have autism, it may work like this: Your boss comes to your desk to talk. A fluorescent light flickers overhead, a co-worker laughs in the next cubicle, and a microwave whirrs in the break room. Your brain filters out those sights and sounds so you can focus on what your boss is saying. You also tune out the sound of a siren outside, but when you smell smoke, you respond to that sensory input and leave the building.

If you have autism, you may process sensory information differently. You may be unable to filter out irrelevant sights or sounds, such as, in the previous example, the flickering light or the microwave. Or you may find certain sounds, lights, smells, or textures to be severely distracting or uncomfortable.

Some suspect that sensory sensitivities may trigger some common behaviors in autistic children, such as very picky eating or running away.

Studying How Autistic People Perceive Sound

To measure sensory symptoms, researchers have used surveys, skin conductance tests, hearing exams, electroencephalograms (EEGs), and brain scans.

A group of British researchers found that autistic teens as a group had the same ability to discriminate sounds overall as their typically developing peers. But there were differences among autistic teens. About 20 percent had exceptional pitch, the ability to distinguish one musical tone from another. Another group of autistic teens, however, had trouble determining the loudness of a tone; those teens were also more likely to be sensitive to noise.⁵

Other researchers wanted to see how children’s autonomic nervous systems, which control involuntary processes such as heart rate, reacted to noise. For this study, they measured skin conductance ─ the response of sweat glands on the hand ─ in children with and without autism.

Children with autism had stronger autonomic reactions than typically developing children when they heard noises, but also when they didn’t.⁶ Their stronger bodily responses may trigger greater behavioral responses to sound, the researchers concluded.

Seeing How the Brain Responds to Sound and Touch

Can you see how the brains of autistic people respond to sound? One research team took scans of children’s brains while exposing them to traffic sounds and scratchy fabric. The youth with autism showed greater activity in certain brain regions than typically developing children on a functional Magnetic Resonance Imaging scan.⁷ Those regions included the amygdala, which is involved in social and emotional behavior, and the cortices that process sensory information.

In another study, researchers collected information from EEGs, in which electrodes are placed on someone’s head to measure electrical activity in the brain. They measured children’s brain waves when they heard beeps and saw the same picture over and over. Typically developing children got used to the beeps and pictures over time, meaning their brains showed a weaker response to them. But the autistic children were less likely to get used to the sounds and pictures.⁸

These studies suggest that the nervous system of children with autism may respond differently to sound.

Why Might Some Autistic Children Underreact to Sound?

Does autism affect hearing in some children? One research group conducted tests to find out. They detected no difference in the hearing of children with and without autism – at least in tests that did not require a behavioral response from the children.

However, things got trickier when they administered a test that required the children to indicate by their behavior that they heard a particular sound. In those tests, 41 percent of the children with autism acted as though they did not hear as expected at least one time.⁹ Researchers repeated the tests and got different results with some of the same children. Their failure to respond consistently and typically to sound may have been caused by a problem with attention, rather than with hearing or sensory processing, they and other researchers theorized.^9-10

Those researchers cautioned that children with autism may appear to have hearing problems on tests that require a behavioral response, even though their hearing is fine. They also said that their findings may undercut some of the assumptions behind auditory integration training (AIT), a treatment that exposes autistic children to filtered music or sounds. Children with autism may perform unreliably on behavioral hearing tests that might be given before and after AIT.⁹

The National Autism Center and the American Speech-Language-Hearing Association concluded that AIT did not have sufficient scientific evidence as an autism treatment. Similarly, a 2017 review by researchers at Vanderbilt University found that interventions based on auditory integration did not improve language in autistic children.¹¹

Other therapies have been used for noise sensitivities in the general population. They include cognitive behavioral therapy to manage fear of noise, and strategies to desensitize people to noise. But there is little research on using those methods with autistic people.¹²

So where may people turn for help?

Navigating a Noisy World

Occupational therapists who are trained in sensory processing may help. They can recommend ways to manage noise sensitivity, such as noise-cancelling headphones and strategies to stay calm in loud places.

U.S. special education law and the Americans with Disabilities Act provide other options, called accommodations. Parents can ask schools to allow their children to be seated away from loudspeakers and chatty classmates, take tests in a quiet room, and be warned about a scheduled fire drill, for example.

Autistic employees can ask for quieter work areas and other “reasonable accommodations” based on their individual needs. Visit the U.S. Department of Labor’s Job Accommodations page to learn more.

Interested in joining SPARK? Here’s what you should know.

References

1. Kanner L. Nervous Child 2, 217-250 (1943)
2. Donvan J. and C. Zucker (October 2010) The Atlantic. Accessed Nov. 14, 2023.
3. Williams Z.J. et al. Ear Hear. 42, 1137-1150 (2021) PubMed
4. Schaaf R.C. and A.E. Lane Autism Dev. Disord. 45, 1380-1395 (2015) PubMed
5. Jones C.R.G. et al. Neuropsychologia 47, 2850-2858 (2009) PubMed
6. Chang M.C. et al. Am. J. Occup. Ther. 66, 567-576 (2012) PubMed
7. Green S.A. JAMA Psychiatry 72, 778-786 (2015) PubMed
8. Jamal W. et al. J. Autism Dev. Disord. 51, 3153-3164 (2021) PubMed
9. Tharpe A.M. et al. Ear Hear. 27, 430-441 (2006) PubMed
10. Ceponiene R. et al. Proc. Natl. Acad. Sci. USA 100, 5567-5572 (2003) PubMed
11. Weitlauf A.S. et al. Pediatrics 139, e20170347 (2017) PubMed
12. Danesh A.A. et al. Audiol. Res. 11, 547-556 (2021) PubMed