Next-generation hearing aids emulate fly’s ability to pinpoint sound

ere is a fly that can locate a cricket from the sound it makes, despite other noises in the background. Yet the hearing mechanism that helps the fly do this spans only 1.5 mm, which is 50 times smaller than the wavelength of the cricket’s chirp. Now, engineers have found a way to mimic the fly’s super-hearing in a tiny device that does not require a bulky battery.

A paper describing the work is published in the journal Applied Physics Letters.

The engineers, from the Cockrell School of Engineering at the University of Texas at Austin, say the new device could be used in a new generation of hypersensitive hearing aids that use intelligent microphones to select only those sounds or conversations that the wearer wants to hear.

Fly’s sophisticated hearing can locate a cricket with remarkable accuracy

Neal Hall, an assistant professor in the Cockrell School’s Department of Electrical and Computer Engineering, and his team of graduate students, drew their inspiration from pioneering work by Ronald Miles at Binghamton University, NY, and Ronald Hoy at Cornell University, Ithaca, NY.

 

They were the first to describe the technological potential of emulating the super-hearing mechanism of the yellow-colored parasitoid flyOrmia ochracea, which stalks and locates male field crickets from their chirps and lays live larvae on and around them.

The fly can locate the cricket with remarkable accuracy because it has a sophisticated sound processing mechanism that determines the direction of the sound within an angle of 2 degrees.

Using the fly’s super-evolved hearing structure as a model, Prof. Hall and colleagues made a tiny pressure-sensing device out of silicon. With a span of only 2 mm, the device is nearly the same size as the fly’s hearing organ.

Unlike many insects, the reason humans and other mammals can pinpoint the source of a sound is because we have a much larger distance between our ears. The sound processing mechanism in our brains uses the time difference in the arrival of the sound at the two ears to locate the source.

But insects’ bodies are generally too small to do this – the sound waves effectively hit both sides almost at the same time.

That is, except for insects like O. ochracea – it can locate the direction of a cricket’s chirp even though its ears are less than 2 mm apart. Its highly evolved hearing mechanism can sense the 4 millisecond gap between the sound entering one ear and the other. It also amplifies this time difference using a “teeter-totter” or “see-saw” mechanism that allows it to locate the cricket with remarkable accuracy.

Engineers emulated fly’s hearing mechanism using a flexible beam

To replicate the fly’s hearing mechanism, the team made a flexible beam incorporating piezoelectric materials that allowed them to use the flexing and rotation of the beam as a way to measure sound pressure and pressure gradient at the same time.

While other teams have already tried to build hearing devices that emulate the fly’s super-hearing, Prof. Neal and colleagues are the first to use piezoelectric materials, which convert mechanical pressure into electrical signals and allow the device to work with very little power.

“Because hearing aids rely on batteries, minimizing power consumption is a critical consideration in moving hearing-aid device technology forward,” says Prof. Hall.

He sees this technology being attractive to people with hearing problems in the future. While as many as 1 in 10 Americans could benefit from a hearing aid, currently only a fifth of this number use one, he adds.

He says many believe the main reason for the gap is hearing aid wearers’ dissatisfaction with the devices:

“Turning up the volume to hear someone across from you also amplifies all of the surrounding background noise – resembling the sound of a cocktail party.”

As well as taking hearing aid technology to a new level, the device could also be useful in military and defense applications. For example, in dark environments where visual cues are absent.

Funds from the Defense Advanced Research Projects Agency (DARPA) helped finance the study.

In February 2014, Medical News Today reported how researchers have developed a new low-powered chip that offers the prospect of cochlear implants without external hardware.

Written by Catharine Paddock PhD

http://www.medicalnewstoday.com/articles/280000.php

 

 

 

Tinnitus affects processing of emotions

Patients with persistent ringing in the ears – a condition known as tinnitus – process emotions differently in the brain from those with normal hearing, researchers report in the journal Brain Research.

Tinnitus afflicts 50 million people in the United States, according to the American Tinnitus Association, and causes those with the condition to hear noises that aren’t really there. These phantom sounds are not speech, but rather whooshing noises, train whistles, cricket noises or whines. Their severity often varies day to day.

University of Illinois speech and hearing science professor Fatima Husain, who led the study, said previous studies showed that tinnitus is associated with increased stress, anxiety, irritability and depression, all of which are affiliated with the brain’s emotional processing systems.

“Obviously, when you hear annoying noises constantly that you can’t control, it may affect your emotional processing systems,” Husain said. “But when I looked at experimental work done on tinnitus and emotional processing, especially brain imaging work, there hadn’t been much research published.”

She decided to use functional magnetic resonance imaging (fMRI) brain scans to better understand how tinnitus affects the brain’s ability to process emotions. These scans show the areas of the brain that are active in response to stimulation, based upon blood flow to those areas.

Three groups of participants were used in the study: people with mild-to-moderate hearing loss and mild tinnitus; people with mild-to-moderate hearing loss without tinnitus; and a control group of age-matched people without hearing loss or tinnitus. Each person was put in an fMRI machine and listened to a standardized set of 30 pleasant, 30 unpleasant and 30 emotionally neutral sounds (for example, a baby laughing, a woman screaming and a water bottle opening). The participants pressed a button to categorize each sound as pleasant, unpleasant or neutral.

The tinnitus and normal-hearing groups responded more quickly to emotion-inducing sounds than to neutral sounds, while patients with hearing loss had a similar response time to each category of sound. Over all, the tinnitus group’s reaction times were slower than the reaction times of those with normal hearing.

Activity in the amygdala, a brain region associated with emotional processing, was lower in the tinnitus and hearing-loss patients than in people with normal hearing. Tinnitus patients also showed more activity than normal-hearing people in two other brain regions associated with emotion, the parahippocampus and the insula. The findings surprised Husain.

“We thought that because people with tinnitus constantly hear a bothersome, unpleasant stimulus, they would have an even higher amount of activity in the amygdala when hearing these sounds, but it was lesser,” she said. “Because they’ve had to adjust to the sound, some plasticity in the brain has occurred. They have had to reduce this amygdala activity and reroute it to other parts of the brain because the amygdala cannot be active all the time due to this annoying sound.”

Because of the sheer number of people who suffer from tinnitus in the United States, a group that includes many combat veterans, Husain hopes her group’s future research will be able to increase tinnitus patients’ quality of life.

“It’s a communication issue and a quality-of-life issue,” she said. “We want to know how we can get better in the clinical realm. Audiologists and clinicians are aware that tinnitus affects emotional aspects, too, and we want to make them aware that these effects are occurring so they can better help their patients.”

http://www.medicalnewstoday.com/releases/278846.php

Picture courtesy of tinnitusart.com