Tinnitus is estimated to affect 10 percent of the population at some stage, and is more common in the over 65s.
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Neuroscientist Grant Searchfield, from the University of Auckland, says for some of those who experience it, tinnitus is a huge problem.
"Often it's not so much that [the sounds are] particularly loud - it's their persistence and your inability to walk away from it, says Searchfield.
"It can disrupt their sleep, attention, affects their ability to perform work. We know that it can affect concentration and attention-related tasks, and affects the hearing as well."
The sounds, perceived by the brain but having no external source, might be high-pitched, like steam hissing out of a kettle, or similar to being surrounded by cicadas at the height of summer.
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Tinnitus is usually triggered by some some sort of change or damage to the hearing system. This sets up a cascade of events where the brain tries to make sense of an altered signal from the ear.
The brain tries to interpret the reduced activity in the hearing system the best way it can and creates a phantom sound.
Searchfield says the brain also amplifies background activity which occurs constantly in the auditory system "because the brain is never silent".
"Tinnitus is the sound of the absence of sound," he says.
Associate Professor Grant Searchfield Photo: Supplied
It's a physical event, not psychological, and is not imaginary.
Underlying it is a change in activity and firing in the auditory nerve.
"When a nerve fibre fires, the brain codes it as silence. But when the firing takes on a particular pattern that resembles sound, then the brain will hear it as sound."
Noise exposure is responsible for around 40 percent of cases, mostly recreational noise rather than from the workplace.
The length of time we're exposed to noise is a significant factor, Seachfield says.
The ease with which we can now listen to music in longer sessions gives us a much larger "dose" of sound.
"You can conveniently listen to a very long playlist and until a rechargeable battery runs out. The old Walkman - the tape cassette - you'll come to the end of one side and have to change it over - and that time would give the ears a break."
Coping with tinnitus 'not about willpower'
Many people live with tinnitus and have learned to cope, Searchfield says. But it's not a matter of willpower, it's about how the brain works.
Tinnitus is deeply rooted in a survival mechanism that takes over when we hear something threatening.
"People we find are most likely to have a reaction to tinnitus at a particular time, may be undergoing a fair amount of stress. They may be overly anxious and concerned or the tinnitus itself may create that."
Key to reducing distress is to break the connection between hearing the sound and reacting to it.
"Once you realise it's there and you become a little bit more concerned about it, often what will happen is that you'll pay more attention to it.
"Once you start paying more attention to it you're more aware of it, so you pay more attention to it, so this vicious cycle starts to arise.
"You essentially learn to become very good at listening to your tinnitus."
Though people vary in their innate ability to filter out sound, training can help, Searchfield says, and strategies using sound are very good.
"The worst situation for most people with tinnitus is when you're in a really quiet environment ... that's why it's often worse at night".
Podcasts and treatment sounds are available to download onto smartphones and hearing-aid manufacturers have tools to both help with hearing and provide treatment sounds.
In some cultures the sound is considered a blessing. "It's perceived as god or a deity talking to you in a positive light. If you see this sound as a blessing you're unlikely to have a problem with it."
Researchers are working on finding a cure but "that will be some way off", he says.
Prof Searchfield is giving free public lecture at 10.30am on 8 February, at St Chad's Church and Community Centre, Meadowbank, Auckland. It is being made available later on the National Foundation for the Deaf website. The University of Auckland also runs Tinnitus Tunes, an information and treatment programme.