Is the Tech Behind Hearing Loss Simulations Accurate Enough?June 4, 2014
"Wow, you sure couldn't have asked for a better day for cooking outside," a man says over a sizzling barbecue. Children play and yell in the distance, and birds chatter directly above my head. "I can't wait 'til everyone tries my new recipe," he continues.
Though his voice is near, it's difficult to hear him clearly. The background noise makes understanding him a challenge, and certain consonants — the "t" in "couldn't," and the "s" and "k" in "asked," for example — sound dull, making the man's words seem incomplete.
I am experiencing mild hearing loss.
But I don't have a hearing impairment, and this man isn't speaking to me in real life. His voice seeps through my earphones during an online simulation from Starkey Hearing Technologies. It's one of several digital tools that allows people with normal hearing to walk a mile, or a few feet, in the shoes of someone with hearing loss.
According to the World Health Organization, 360 million people around the world have disabling hearing loss — more than 5% of the global population. Nearly 50 million Americans experience hearing loss, including one in five teens and 47% of adults aged 75 or older. It's also associated with war: 60% of veterans returning from Iraq and Afghanistan return with hearing loss and tinnitus.
More hearing loss simulators like Starkey's are available online, including one from the Hear the World Foundation and a video (below) from the House Ear Institute. They aim to portray the experience of hearing loss for parents, partners and friends of people with hearing impairments, as well as the generally curious public.
But how accurate are these simulations, and what goes into creating them? Are they even the best way to communicate hearing loss to those who hear normally?
Dr. Brian Moore, a specialist in the perception of sound and leader of the Auditory Perception Group at the University of Cambridge, believes these types of simulations are the best we have, at the moment. Moore has researched how the auditory system works, the relationship between sound stimuli and what we actually perceive, and the changes in perception that occur when people have hearing loss.
In 1995, he published Perceptual Consequences of Cochlear Damage with an accompanying audio CD, which included eight demonstrations that simulated the effects of hearing loss. Over the past 19 years, Moore and his colleagues have modified the demonstrations with minor tweaks.
"We know that these simulations aren't perfect, but they give a reasonable idea" Moore tells Mashable. His team has evaluated its simulations by testing patients who have a hearing impairment in one ear only — the other ear is normal. First, they play a sound through his impaired ear. Then they process that same sound to simulate the hearing loss of his impaired ear and present it to his good ear. That patients evaluates how similar he finds the sounds.
More often than not, they say it matches pretty well, according to Moore.
But the process isn't all trial and error. For instance, simulations are based on measurements of two aspects of hearing impairment that specialists know occur: loudness recruitment, or the ability to detect high levels of sound normally, but not low levels, and reduced frequency selectivity, when the ear can't perceive different frequencies in complex sounds (such as music or overlapping speech).
First measuring a person's sound detection threshold (the lowest sounds he or she can perceive) helps to actually process the simulation, with nearly accurate results.
"Though the simulation doesn't sound very nice to people with normal hearing, it's actually not quite as bad as what the hearing-impaired person is experiencing. So, there's some other dimension that we're missing in these simulations. We're getting close, but we're not quite there," Moore says.
Moore and others have also worked on simulations of what it's like to listen through a cochlear implant.
"Cochlear implants are devices usually given only to people with severe or profound hearing loss, who don't get much benefit from a hearing aid. They are increasingly being used in very young children," Moore says.
The cochlear implant simulations may be even more surprising to the average person — the sound is staticky, but you can pick up what is said. Today's cochlear implants, however, still aren't very good at picking up frequencies in complex sounds, such as music. There's room for improvement in that space, too.
In addition to giving parents, spouses and friends of hearing-impaired people a lot of insight into what their loved ones are experiencing, Moore also believes these simulations can be useful tools in encouraging teens especially to take care of their hearing.
"They should take steps to protect their hearing if they're at a very loud concert ... Demonstrations of what it's like to have a hearing loss can be effective in persuading people about that."
You can find some of Moore's latest simulations on the Action on Hearing Loss website, a nonprofit that supports hearing loss research in the UK. The site even lets you check if you have hearing loss, with an easy quiz.
"It's by no means perfect," Moore says, again, of these simulations. "But we're fairly confident we're on the right lines."