Most of us know it as that ringing sound we hear after a loud concert, but an estimated 45 million Americans experience some form of the condition, which is called tinnitus, with 20 million constantly suffering from it, unsure of where the sound is coming from. But now, a new study has shed some light on the source of that sound.

Taking advantage of a rare opportunity to observe the brain of someone with tinnitus — this person had to undergo surgery for epilepsy — researchers from the University of Iowa and Newcastle University discovered that the condition affects areas of the brain beyond the primary auditory cortex. They found this person’s brain was also active in the areas involved with the broader perceptions of noises, including those that control attention, memory, and emotion, New Scientist reported.

“It’s like when you’re walking home on a dark night and you can hear every little flicker of sound that would normally go unnoticed,” Will Sedley, of the Institute of Neuroscience at Newcastle, told New Scientist. “Maybe in people with tinnitus, the ‘high alert’ activity somehow kicks in, gains access to wider perception networks in the brain, and is difficult to dislodge.”

In other words, tinnitus may occur when the brain amplifies sounds that normally wouldn’t enter our consciousness.

The researchers discovered this while conducting invasive electrode monitoring in a 50-year-old epileptic man who also happened to have tinnitus in both ears due to hearing loss. Awake during the surgery, the man had recording electrodes placed in various parts of his brain to identify the source of his seizures.

Meanwhile, Sedley’s team tested the man’s tinnitus by measuring brain activity while suppressing it with white noise for 30 seconds, and then allowing it to return — after about 10 seconds of turning off the white noise. The man was also asked to rate the loudness of the tinnitus before the white noise was turned on, right after it was turned off, and about 10 seconds later. They did this several times over the course of two days before concluding brain activity was more widespread. Even when they played a sound mimicking tinnitus, it was perceived in a centralized area.

“We now know that tinnitus is represented very differently in the brain to normal sounds, even ones that sound the same,” Sedley said in a press release, while noting this may be the reason why current treatments aren’t always effective.

Currently, the most effective treatment for tinnitus is acoustic  neural stimulation, in which a device alters the brain’s waves and eases the constant sound. Besides that, however, counseling and sound generators don’t actually treat the problem, and instead rely on teaching a person how to cope with the ringing. The new study offers new insight into the way tinnitus works, and may eventually lead to more effective treatments, Sedley said.

Source: Sedley W, Gander P, Kumar S, et al. Intracranial Mapping of a Cortical Tinnitus System using Residual Inhibition. Current Biology. 2015.