How Your Brain Builds the World of Sound — Inside The Sound Barrier

How the Brain Builds the World of Sound

In the 1970s, psychologist Diana Deutsch was experimenting with a synthesizer when she encountered a startling auditory illusion. "It felt as if I had stepped into another universe or gone mad — the world just flipped over," she later recalled. Deutsch's "Octave Illusion" was more than a curiosity: it revealed that perception is an active construction by the brain, not a direct readout from the ears.

The brain as an editor

What reaches our consciousness is the brain's best interpretation of incoming sound. As Professor Dan Polley explains, "Because the brain doesn’t have direct contact with the physical world, everything we experience as consciousness is assembled from brain activity." That editing ability helps us parse speech in noise, recognize music, and even reconstruct sound after hearing loss.

Relearning sound: cochlear implants

The brain's reconstructive power makes technologies like cochlear implants possible. These devices deliver a new kind of electrical input, and patients must retrain their brains to interpret it. In the series, Noam speaks with a listener who used recordings of Winnie the Pooh to help his brain relearn how to enjoy Ravel's "Bolero" after hearing was restored.

Tinnitus and hidden hearing loss

Nearly 15% of adults experience tinnitus — a persistent sound heard only inside the head. Many of these people test as "normal" on standard audiograms, which led some to dismiss tinnitus as psychosomatic. New research into hidden hearing loss shows that damage to synapses or nerve fibers can produce tinnitus and other deficits that conventional hearing tests miss. Key questions remain: why do some people with similar damage develop tinnitus while others do not, and what treatments are effective?

Silence: more than nothing

Silence is paradoxical. In one study, participants left alone in a quiet room for 15 minutes often preferred to self-administer an electric shock than remain in silence. Yet silence and certain forms of sensory deprivation can reduce anxiety and aid recovery from PTSD. In mice, exposure to silence increased neurogenesis more than exposure to other sounds. The series explores whether silence is itself a perceivable event, revisits John Cage's 4'33" (which reframes ambient sound as music), and visits some of the world's quietest places.

Listening to the cosmos

Turning data into sound — sonification — lets researchers "hear" phenomena that are otherwise invisible. Wanda Díaz-Merced, who became blind in college, first recognized a recording as one of the largest solar storms ever and described the experience as a life-changing transformation: noise turned into beauty. The series also features Nobel laureate Robert Wilson, whose work with radio observations contributed to evidence for the Big Bang, and Kim Arcand's sonification of the Milky Way's center.

About the series

The Sound Barrier is a four-part series from Unexplainable that probes how hearing works, how it can fail, and how scientists and patients reclaim sound. Episodes explore auditory illusions, cochlear implants, tinnitus and hidden hearing loss, the surprising effects of silence, and the science of listening to space. New episodes will be released every Monday and Wednesday starting November 3.

“Perception is not a passive receiving of information — it’s an active process of construction,” — series interviews and research show.