Almost everyone reacts with discomfort when they hear the sound of a fingernail scraping on a blackboard or the screeching of chalk on slate, and they also tend to cringe when they hear the high-pitched hum of a dentist's drill.

But there are common sounds that hardly bother most people, if at all, yet drive others absolutely up the wall. The scientific name for this is misophonia, derived from the Greek for "hatred of sound."

Typical triggers are sounds of other people eating or nose/throat sounds, such as chewing noisily, slurping, lip-smacking, throat-clearing, gurgling or sniffing. Other sorts of sounds can set people off, too, including finger tapping, a clock ticking, a pen clicking, water dripping, paper rustling or Styrofoam squeaking.

"A way to describe it is that some people are able to tolerate certain sounds less well than others are," says Anne Möllmann, a psychological psychotherapist and director of studies at Bielefeld University in Germany.

Psychologists at the school have been studying misophonia since 2014. Although not yet officially recognized as a distinct disorder, it's "really a frequent phenomenon," Möllmann says and is estimated to affect about 5% of the population.

Misophonia sufferers aren't merely annoyed by certain sounds – usually ones made by others that others don't pay attention to – but have strong emotional responses such as anger, disgust and aggression.

"Physiological reactions such as palpitations, profuse sweating or nausea aren't unusual," remarks Andreas Seebeck, a non-medical practitioner of psychotherapy who has specialized in misophonia for the past eight years. His son, from the age of 12, could hardly bear hearing his mother chewing.

"We were pretty much at our wits' end," Seebeck says. "It was hugely stressful."

The offending sounds typically aren't made by strangers – for example, someone at a nearby table in a restaurant – but by people the sufferer has a close relationship with. "This makes it extremely distressing for all concerned because the people are often loved ones they spend a lot of time with," says Möllmann.

Trouble tolerating the sounds that someone makes when eating often causes a strong feeling of guilt, especially if the maker of the sounds is a romantic partner. Researchers now know, however, that misophonia isn't an expression of long pent-up relationship problems – even children can suffer from it.

Many questions remain unanswered, for example, why certain sounds are so maddening to some people. According to Möllmann, an affected person's ears have nothing to do with it. Rather, she suggests, the sound is somehow processed differently on its way to the brain.

This can evoke strong reactions "wholly disproportionate" to the nature of the sound, she remarks.

Seebeck says misophonia seems to involve a classic conditioned response – that is, an acquired response to a stimulus that was previously neutral. He describes a common situation that can give rise to such a response: children displeased by being made to remain at the dining table although they've finished eating.

"This can sensitize them to the chewing noises they then hear from family members," he explains, which, of course, doesn't mean they don't like the people doing the munching and crunching.

"All parents need to do is allow their children to leave the table," advises Seebeck. "It would prevent many, many cases [of misophonia]."

He says it's useless trying to get someone repulsed by eating sounds to learn to bear them. While repeated exposure to the source of phobias can help people overcome them, misophonia is different, according to Seebeck, who says the more that misophonics are exposed to sounds they detest, the more they feel "unending rage."

So, what's the remedy for misophonia at the dining table? Möllmann says that wearing headphones or earplugs or listening to background music can help at least temporarily. But to solve the problem for good, she says meals have to be arranged in a way that's acceptable to the sound-sufferer.

In some families and relationships, the members or partners eat separately. "This isn't an ideal strategy because people typically would prefer to spend this time together," concedes Möllmann. "But we don't discourage it during [misophonic] phases when there's no other choice."

Since the suffering caused by misophonia can be intense, she sees psychotherapy as a useful option. "In any case, this disorder should be taken seriously," she says.

If left untreated, researchers have found that misophonia can lead to complications, including social anxiety and depression.