Having difficulty listening to conversations in noisy cafes and social gatherings could soon be a thing of the past for the hearing impaired, due to technology that cuts through background noise, according to a press release from the HEARing Cooperative Research Centre (HEARing CRC) at the University of Melbourne in Australia. The technology was developed by researchers at the HEARing CRC, the university, and the National Acoustic Laboratories (NAL) in Sydney, and initial testing has shown it can improve speech understanding in noisy environments by up to 50% for hearing aid users.
Following are a selection of interesting news items from our field. This section will be updated on a continuous basis so check back often in between issues, to see what is new.
A cochlear implant that can be wirelessly recharged would use the natural microphone of the middle ear rather than a skull-mounted sensor.
Larry Hardesty, MIT News Office
Cochlear implants — medical devices that electrically stimulate the auditory nerve — have granted at least limited hearing to hundreds of thousands of people worldwide who otherwise would be totally deaf. Existing versions of the device, however, require that a disk-shaped transmitter about an inch in diameter be affixed to the skull, with a wire snaking down to a joint microphone and power source that looks like an oversized hearing aid around the patient’s ear.
Researchers at MIT’s Microsystems Technology Laboratory (MTL), together with physicians from Harvard Medical School and the Massachusetts Eye and Ear Infirmary (MEEI), have developed a new, low-power signal-processing chip that could lead to a cochlear implant that requires no external hardware. The implant would be wirelessly recharged and would run for about eight hours on each charge.
The researchers describe their chip in a paper they’re presenting this week at the International Solid-State Circuits Conference. The paper’s lead author — Marcus Yip, who completed his PhD at MIT last fall — and his colleagues Rui Jin and Nathan Ickes, both in MIT’s Department of Electrical Engineering and Computer Science, will also exhibit a prototype charger that plugs into an ordinary cell phone and can recharge the signal-processing chip in roughly two minutes.
“The idea with this design is that you could use a phone, with an adaptor, to charge the cochlear implant, so you don’t have to be plugged in,” says Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor of Electrical Engineering and corresponding author on the new paper. “Or you could imagine a smart pillow, so you charge overnight, and the next day, it just functions.”
Existing cochlear implants use an external microphone to gather sound, but the new implant would instead use the natural microphone of the middle ear, which is almost always intact in cochlear-implant patients.
The researchers’ design exploits the mechanism of a different type of medical device, known as a middle-ear implant. Delicate bones in the middle ear, known as ossicles, convey the vibrations of the eardrum to the cochlea, the small, spiral chamber in the inner ear that converts acoustic signals to electrical. In patients with middle-ear implants, the cochlea is functional, but one of the ossicles — the stapes — doesn’t vibrate with enough force to stimulate the auditory nerve. A middle-ear implant consists of a tiny sensor that detects the ossicles’ vibrations and an actuator that helps drive the stapes accordingly.
The new device would use the same type of sensor, but the signal it generates would travel to a microchip implanted in the ear, which would convert it to an electrical signal and pass it on to an electrode in the cochlea. Lowering the power requirements of the converter chip was the key to dispensing with the skull-mounted hardware.
Chandrakasan’s lab at MTL specializes in low-power chips, and the new converter deploys several of the tricks that the lab has developed over the years, such as tailoring the arrangement of low-power filters and amplifiers to the precise acoustic properties of the incoming signal.
But Chandrakasan and his colleagues also developed a new signal-generating circuit that reduces the chip’s power consumption by an additional 20 to 30 percent. The key was to specify a new waveform — the basic electrical signal emitted by the chip, which is modulated to encode acoustic information — that is more power-efficient to generate but still stimulates the auditory nerve in the appropriate way.
The waveform was based on prior research involving simulated nerve fibers, but the MIT researchers tailored it for cochlear implants and found a low-power way to implement it in hardware. Two of their collaborators at MEEI — Konstantina Stankovic, an ear surgeon who co-led the study with Chandrakasan, and Don Eddington — tested it on four patients who already had cochlear implants and found that it had no effect on their ability to hear. Working with another collaborator at MEEI, Heidi Nakajima, the researchers have also demonstrated that the chip and sensor are able to pick up and process speech played into a the middle ear of a human cadaver.
“It’s very cool,” says Lawrence Lustig, director of the Cochlear Implant Center at the University of California at San Francisco. “There’s a much greater stigma of having a hearing loss than there is of having a visual loss. So people would be very keen on losing the externals for that reason alone. But then there’s also the added functional benefit of not having to take it off when you’re near water or worrying about components getting lost or broken or stolen. So there are some important practical considerations as well.”
Lustig points out that the new cochlear implant would require a more complex surgery than existing implants do. “A current cochlear-implant operation takes an hour, hour and a half,” he says. “My guess is that the first surgeries will take three to four hours.” But he doubts that that would be much of an obstacle to adoption. “As we get better and better and better, that time will shorten,” he says. “And three to four hours is still a relatively straightforward operation. I don’t anticipate putting a lot of extra risk into the procedure.”
Reprinted with permission of MIT News
The likelihood of hearing loss has always far greater for those who work in the high-noise industrial sector. Despite the predominance of males employed in mining, forestry and automotive body shops, Regina St. Denis, deaf/blind intervenor with the Canadian Hearing Society, said the vast majority of her clients here in Timmins, ON, are female. It may be attributable to the fact women live longer so they are the ones more likely to experience the combined loss of vision and hearing due to age.
A woman in Taiwan had an unusual cause of her ear pain: a fruit fly larva was wriggling around inside her ear canal.
The 48-year old woman went to the emergency room after experiencing severe ear pain for a day, according to a new report of the case. Doctors removed the woman's hearing aid, and saw bloody fluid in her ear.
An exam revealed a fruit fly larva moving around in her ear canal, and the skin close to her eardrum was eroded, according to the doctors at Tri-Service General Hospital, in Taipei.
The National Hearing Conservation Association (NHCA) will recognize audiologist and educator Richard W. Danielson, PhD, with its Outstanding Hearing Conservationist Award in Las Vegas, NV, in March 2014. This prestigious award, established in 1990, recognizes outstanding contributions and achievements in the field of hearing conservation. The NHCA is pleased to honour Dr. Richard Danielson for his distinguished career as an enthusiastic educator and his productive contributions to national efforts to prevent noise-related hearing loss.
Dr. Danielson is an associate professor at Baylor College of Medicine, Houston, with dual appointments in the Department of Otolaryngology - Head and Neck Surgery and in the Center for Space Medicine. Since 2003, he has been the Manager for Audiology and Hearing Conservation at NASA-Johnson Space Center. There, he leads a NASA program aimed at preventing noise-induced hearing loss (during spaceflight and ground-based missions) among NASA’s astronauts, pilots, and other employees. He also collaborates with NASA and international partners towards resolution of auditory and acoustic issues on the International Space Station.
Prior to his work with NASA, Colonel (Ret.) Danielson held several senior leadership positions in the U.S. Army during his 28-year career, which included serving during Operation Desert Storm as the officer-in-charge of the first Audiology Task Force ever deployed to a combat theater. In addition to his exceptional military career, Dr. Danielson has held numerous national leadership roles in several audiology-related professional organizations. He has chaired the Council for Accreditation in Occupational Hearing Conservation (CAOHC) and served for 13 years on its national council, where he was instrumental in revising CAOHC’s curricula for certification and recertification of course directors and professional supervisors of audiometric monitoring. Dr. Danielson recently served as chair of the American Academy of Audiology Foundation Board of Trustees, and has been the president of the Texas Academy of Audiology, the Washington Society of Audiology, and the Military Audiology Association, He has held faculty appointments at 11 universities, where he has taught, supervised research, published, and mentored doctoral candidates, graduate students, medical residents, and audiology interns.
NHCA’s presentation of the Outstanding Hearing Conservationist Award recognizes Dr. Danielson’s lifelong campaign to persuade others to become, what he calls, “evangelists for hearing conservation,” sharing a truly devoted enthusiasm for hearing loss prevention.
Dr. Danielson’s acceptance of the Outstanding Hearing Conservationist Award will take place at an awards luncheon during the NHCA’s 39th Annual Conference to be held March 13-15, 2014 in Las Vegas, Nevada. Many of his colleagues and associates will be on hand to honour and recognize this prestigious achievement. For more information about the NHCA Conference, “Stop Gambling With Your Hearing,” go to http://www.hearingconservation.org.
Noise at an NHL Playoff Game Equivalent to Sitting Next to a Chainsaw for 3 Hours
Spectators at pro sports games like the Super Bowl need to protect their ears while enjoying the action, Canadian experts say.
When the home team scores during a NHL playoff game, the noise in the stands can be as loud as a plane taking off.
“Each time your ears have been ringing, that is evidence of hearing loss. There's no recovery mechanism in place for the death of those inner ear cells,” said Dr. Tim Rindlisbacher, director of sports health at Cleveland Clinic in Toronto, where he also works with the CFL’s Toronto Argonauts and Mississauga SteeIheads of the Ontario Hockey League.
Prof. Bill Hodgetts of the department of speech pathology and audiology at the University of Alberta in Edmonton published a study in 2006 in the Canadian Medical Association Journal, titled Can Hockey Playoffs Harm Your Hearing? to raise awareness about noise when people are enjoying themselves at a game.
The noise of an entire NHL playoff game was equivalent to sitting next to a chainsaw for three hours, said Hodgetts, who is also with the the university's Institute for Reconstructive Sciences in Medicine. When the home team scored, temporarily the noise was like a plane taking off.
Researchers at the University of Texas at Austin have developed an acoustic circulator, a one-way sound machine that could lead to the sound equivalent of a one-way mirror. "I can listen to you, but you cannot detect me back, you cannot hear my presence," said electrical engineer Andrea Alu, co-author of the study published in the journal Science. The device could lead to several sound insulation applications.
COLLEGE PARK, MD - Call it the Ray Charles Effect: a young child who is blind develops a keen ability to hear things others cannot. Researchers have known this can happen in the brains of the very young, which are malleable enough to re-wire some circuits that process sensory information. Now researchers at the University of Maryland and Johns Hopkins University have overturned conventional wisdom, showing the brains of adult mice can also be re-wired, compensating for a temporary vision loss by improving their hearing.
The findings, published Feb. 5 in the peer-reviewed journal Neuron, may lead to treatments for people with hearing loss or tinnitus, said Patrick Kanold, an associate professor of biology at UMD who partnered with Hey-Kyoung Lee, an associate professor of neuroscience at JHU, to lead the study.
"There is some level of interconnectedness of the senses in the brain that we are revealing here," Kanold said.
"We can perhaps use this to benefit our efforts to recover a lost sense," said Lee. "By temporarily preventing vision, we may be able to engage the adult brain to change the circuit to better process sound."
Kanold explained that there is an early "critical period" for hearing, similar to the better-known critical period for vision. The auditory system in the brain of a very young child quickly learns its way around its sound environment, becoming most sensitive to the sounds it encounters most often. But once that critical period is past, the auditory system doesn't respond to changes in the individual's soundscape.
"This is why we can't hear certain tones in Chinese if we didn't learn Chinese as children," Kanold said. "This is also why children get screened for hearing deficits and visual deficits early. You cannot fix it after the critical period."
Kanold, an expert on how the brain processes sound, and Lee, an expert on the same processes in vision, thought the adult brain might be flexible if it were forced to work across the senses rather than within one sense. They used a simple, reversible technique to simulate blindness: they placed adult mice with normal vision and hearing in complete darkness for six to eight days. After the adult mice were returned to a normal light-dark cycle, their vision was unchanged. But they heard much better than before.
The researchers played a series of one-note tones and tested the responses of individual neurons in the auditory cortex, a part of the brain devoted exclusively to hearing. Specifically, they tested neurons in a middle layer of the auditory cortex that receives signals from the thalamus, a part of the midbrain that acts as a switchboard for sensory information. The neurons in this layer of the auditory cortex, called the thalamocortical recipient layer, were generally not thought to be malleable in adults.
But the team found that for the mice that experienced simulated blindness these neurons did, in fact, change. In the mice placed in darkness, the tested neurons fired faster and more powerfully when the tones were played, were more sensitive to quiet sounds, and could discriminate sounds better. These mice also developed more synapses, or neural connections, between the thalamus and the auditory cortex.
The fact that the changes occurred in the cortex, an advanced sensory processing center structured about the same way in most mammals, suggests that flexibility across the senses is a fundamental trait of mammal’s brains, Kanold said.
UC San Francisco researchers are reporting a detailed account of how speech sounds are identified by the human brain, offering an unprecedented insight into the basis of human language.
The finding, they said, may add to our understanding of language disorders, including dyslexia.
The technique is designed to be an infant-friendly way of measuring brain activity using non-traditional methods, and reportedly will aid in the invention of treatment strategies leveraging neural plasticity present in the first 3 years of life.