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How to make a fake auditory signal?

How to make a fake auditory signal?



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My question is about making fake auditory signals. The ear collects sounds from the environment, which are transformed into a neural signal by the hair cells in the inner ear. This signal is sent through the auditory nerve to the to brain, where it is decoded into a hearing sensation.

Now can we make fake signals and feed them into the auditory nerve to bring it to the brain? E.g., instead of the ear collecting sound, could we use an electrical instrument for collecting sound and convert this signal into a neural signal in the auditory nerve?


Devices that bypass the hair cells in the inner ear and directly stimulate the auditory nerve are called cochlear implants. Cochlear implants are used to treat deafness caused by the loss of hair cells in the cochlea. The hair cells are the sensory cells that convert sound vibrations into electric neural signals (Purves et al., 2001). With state-of-the-art devices, the better performing implant wearers are able to talk over the phone(!) An exclamation mark is in place, because it means they can understand the spoken word without the need for lip reading or sign language. Hence, cochlear implants are the answer to your question, but they definitely are not designed to generate fake signals. Instead, they are used as an effective treatment for deafness and are capable of transmitting meaningful speech information.

Cochlear prosthetics consist of an array of typically 20-24 electrodes that are inserted in the scala tympani of the cochlea. The inner ear is tonotopically organized, which means that high frequencies are coded in the base of the cochlea, while low frequencies are encoded in the tip. Hence, each electrode stimulates a separate frequency band (Fig. 1). By using a microphone and sending the acoustic signal through a filter bank, a number of auditory frequency bands can be obtained equal to the number of electrodes in the implant. After this speech processing step, the acoustic frequency bands are converted into trains of biphasic pulses. These pulse trains are sent to the electrodes in the cochlea, which then activate the auditory nerve directly, effectively replacing the degenerated hair cells in the inner ear (Stronks, 2010).


Fig. 1. Cochlear implant. Source: Mayo Clinic.

References
- Purves et al., Neuroscience (2001) 2nd ed.
- Stronks (2010). PhD thesis, Utrecht University


As @AliceD mentioned, cochlear implant is one of the earliest achievements of neural engineering. However, there are orders of magnitude more inner hair cells (IHC) and even more auditory nerve fibers (AN) in human cochlear than the current cochlear implants offer electrodes. If you are interested in a more detailed model of IHC to AN signal transmission, there are tons of research, for example:

  • Meddis, R. (1986). Simulation of mechanical to neural transduction in the auditory receptor. The Journal of the Acoustical Society of America, 79(3):702-711.
  • Walsh, E. J. and McGee, J. (1987). Postnatal development of auditory nerve and cochlear nucleus neuronal responses in kittens. Hearing Research, 28(1):97-116.
  • Sumner, C. J., Lopez Poveda, E. A., O'Mard, L. P., and Meddis, R. (2002). A revised model of the inner-hair cell and auditory-nerve complex. The Journal of the Acoustical Society of America, 111(5):2178-2188.
  • Heinz, M. G., Colburn, H. S., and Carney, L. H. (2001). Evaluating auditory performance limits: I. One-Parameter discrimination using a computational model for the auditory nerve. Neural Computation, 13(10):2273-2316.

9 Sound Design Hacks for Bigger, Fuller Mixes

It can be deceptively easy to mix and master a track, but what happens to the sound when it leaves the speakers?

Our friends at Get That Pro Sound are here to deliver a crash course on sound design tricks 101 that will seduce your listeners’ ears into hearing exactly what you want. Music producers, pay attention!

Using basic knowledge about psychoacoustic principles, you can find creative ways to bring your listeners a more powerful, clear, and “larger than life” experience. By understanding how our ears interpret sounds, we can creatively and artificially recreate certain responses to particular audio phenomena, particularly EQ, compression, and reverb.


How to Speak Cicada

(Inside Science) -- When you first hear it, a cicada chorus may sound like simple buzzing. But to a cicada, that cacophony is full of meaning.

There are three species in Brood X, the cohort of 17-year cicadas now emerging in much of the eastern U.S. Members of each species congregate with their own kind and talk to each other with their own species-specific sounds. Males sing to court females and "jam" the songs of other males, while females make clicks with their wings to encourage or repel suitors.

Humans can learn to decode these sounds. John Cooley, a biologist at the University of Connecticut, can speak cicada so well he can seduce insects of either sex. He uses his voice to imitate males and gentle finger snaps to imitate females.

"All the females are cueing in on is the pitch and the rhythm," he said. "You hit that, and you're going to get a response."

Males "sing" by vibrating tymbal organs located on the sides of the abdomen. They also produce alarm calls when handled, as seen in this video by Greg Holmes.

Loud or soft?

Cicadas spend most of their lives as juveniles called nymphs, living underground and feeding on fluid from tree roots. Eventually, they dig to the surface, shed their nymphal exoskeletons, and fly into the trees to sing, breed and die.

Most species don't synchronize their emergence instead, a small batch will come out to breed every year. Such species are often called annual cicadas, even though they may live for several years as nymphs.

A male annual cicada will find his own spot from which to sing, and interested females who hear the song will fly to meet him. The louder the male's song, the farther it will travel, and the more females he can call in. As a result, the songs of annual species are often deafeningly loud.

Male annual cicadas like this Neocicada hieroglyphica must call in females from far away, so their songs are often deafeningly loud.

The songs of periodical cicadas, including the 17-year cicadas, sound loud en masse, but each male's song is typically quieter than that of an annual cicada. That's because periodical cicadas emerge on the same schedule, waiting for a set number of years and then all coming out to breed at once. The adults gather in dense choruses with huge numbers of individuals, so there's little point trying to call in females from far away. Instead, periodical cicada males use their songs to get the attention of females that are already nearby.

"It's obvious where the females are. They're right here in this giant pile of bugs," said Cooley. "The chorus is such an acoustical mess anyway, your sound's only going to travel a very short distance before it's washed out in the general chaos."

High or low?

The three species now emerging in Brood X -- Magicicada septendecim, M. cassini and M. septendecula -- have the longest documented lifespans of any cicadas in the world, according to Floyd Shockley, an entomologist with the Smithsonian National Museum of Natural History in Washington. Different regions have their own broods that emerge in different years, but all broods containing those three species are on 17-year schedules.

Females only want to mate with males of their own species, and songs are how they tell the difference. Species that emerge together in the same brood typically have songs that are easy to tell apart.

In Brood X, M. septendecim's song is low and haunting, resembling "a UFO landing or a strange musical note in the woods," said David Marshall, an evolutionary biologist with the University of Connecticut. M. cassini's is similar to M. septendecim's in structure, but higher and faster. M. septendecula has a more complicated song made up of rapid pulses that change tone half way through.

In the early 2000s, Cooley and Marshall discovered a previously unknown cicada species that appears to have changed its song to avoid being mistaken for its neighbors. While they can't be sure how the new species arose, evidence suggests the process started when some of the 17-year M. septendecim switched to a 13-year schedule. Marshall suspects the split happened at least several thousand years ago.

In the northern edge of its range, the new species, dubbed M. neotredecim, doesn't encounter any similar-sounding species, and it retains the song of its 17-year ancestors. But farther south, it meets another closely related 13-year species, M. tredecim, which sounds almost the same. In areas where M. neotredecim and M. tredecim emerge together, the new species appears to have shifted to a higher pitch. Evidently, the females' need to identify their own species was so strong that it drove males to evolve from baritones to tenors.

To click or not to click?

For a long time, the courtship rituals of cicadas in the Magicicada genus appeared to make little sense. The males would go through an elaborate series of songs and behaviors, while the females, to all appearances, "just sat there like lumps," said Cooley.

What was missing was a signal by the female to show she approved of a male's efforts. Researchers in the late 70s failed to spot it, and so did Marshall during his first field season in 1991. But four years later, Cooley and Marshall noticed what the male cicadas had been watching for all along: a flick of the female's wings that produced a soft click.

This wing-flick signal means "yes, come mate with me" -- but only if done at precisely the right time. Performed at any other time, it means "go away, I'm not interested."

To make matters worse, nearly all the wing-flicks one sees are of the "go away" variety, because females typically mate only once. By the time most researchers spotted the "come hither" wing-flick, they had already seen so many of the other kind that they'd learned to discount it.

"The females that you see obviously out in the chorus are the ones that are either not yet ready to mate, or they have already mated, and so they're not interested in mating," said Cooley. "They come into sexual receptivity unpredictably and gradually, and then they flick their wings, and boom, they're out of the mating pool."

Because mating opportunities are so rare, males will pursue anything that seems even vaguely promising. If a random movement or clicklike sound occurs at the right time, a male may mistake it for a receptive female.

"They'll try to mate with acorns. They'll try to mate with spiders. Anything," said Cooley. This was fortunate for the researchers, because it allowed them to perform experiments by snapping their fingers and posing miscellaneous objects as model cicadas. The caps of Sharpie pens worked well, being about the same size and color as a female cicada. So did an old light switch, which had "plenty of places on it where the male can attach his genitalia," said Cooley.

This video by Greg Holmes shows courtship and mating in Magicicada tredecim, a 13-year species that is very similar to M. septendecim.

The experiments confirmed how the wing-flick signals work, which in turn unlocked the whole process. A hopeful male will give a call, which for most Magicicada species consists of a sustained note that falls in pitch at the end. Then he will pause, watching and listening for a potential partner. If no one replies, he'll continue searching through the throng, often flying a short distance before trying again.

When a female does signal approval, the male will approach her, shifting to a faster series of calls with little pause in between. If another male tries to court the same female, the first male may sing over top of his rival's call, preventing the female from hearing the down-slurred ending that would entice her to reply.

When the male reaches his intended, he extends a tentative foreleg that often vibrates gently as he touches her. Then, if she allows it, he will climb aboard, shifting to a staccato song that lacks the down-slur. He keeps crooning until his body connects with hers.

Editor's note (May 28, 2021): This article was edited after publication to clarify when David Marshall believes the species M. septendecim and M. neotredecim split and the date of his first field season.


How to Make a Kaleidoscope Without Mirrors

Making a kaleidoscope without mirrors provides a fun way to view the outside world. A kaleidoscope distorts images and colors, making ordinary objects look unique, interesting and colorful. Kaleidoscopes made without mirrors use transparency film instead of mirrors to provide a reflective surface, allowing students from elementary to college levels to produce a kaleidoscope without handling sharp, breakable mirror pieces. Using a few household items, you can make a kaleidoscope in no time at all and enjoy the vibrant and flashy images your kaleidoscope can create.

Trace the top of the paper towel roll onto the folder, and cut out the traced circle. In the center of the circle, punch a hole in the center of the circle with the hole punch 1. This hole will become the eye-hole for your kaleidoscope.

Measure the outer edge of the circle with the compass. Mark every 1.5 cm around the circle and make small cuts with scissors on the marks. The cuts will form tabs around the edge of the circle.

Cut a piece of transparency film large enough to cover the eye-hole on the circular piece. With rubber cement, glue the transparency film down over the eye-hole. Place the circle on one end of the paper towel roll, fold the tabs down and secure with masking tape.

Cut the file folder, black construction paper and transparency film into three 6.5-by-27-cm strips. Glue the strips together by placing the black construction paper on top of the folder, then the transparency film. When finished, you should have three sets of layered strips. The transparency film on top of the black paper will provide a mirror-like surface.

Place the strips on your work surface, transparency side down, side by side. Put masking tape on the top and bottom of the strips, on the folder side. Fold the taped strips to form a triangle with the transparent side on the inside, tape the triangle together and place the triangle into the open end of the tube.

Cut out two circles of transparency film the exact way you made the piece of folder that became the eyepiece. Cut each piece of transparency film to the same size as the circle you traced from the paper towel roll cut tabs into it without the eye-hole.

Place one of the transparency circles into the open end of the tube so that the circle touches the mirrored column and the tabs face outward. Secure the circle to the paper towel roll with tape, and place sequins into the open end of the tube.

Place the other transparency circle over the open end of the tube on top of the sequins. Fold down the tabs onto the outside of the paper towel roll, and secure with tape.

Try adding glitter, rocks or bits of tissue paper to the kaleidoscope. You have many choices be creative and experiment with new items.


A few simple tricks make fake news stories stick in the brain

Purveyors of deceitful messaging use a few key tricks that take advantage of the brain’s desire to believe.

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Bad information isn’t new. Propagandists and scam artists have been selling their brand of proverbial snake oil for ages, all to bend people’s thinking to their goals. What’s different today is that the digital world flings information faster and farther than ever before.

Our brains can’t always keep up.

That’s because we often rely on quick estimates to figure out whether something is true. These shortcuts, called heuristics, are often based on very simple patterns (SN: 9/20/14, p. 24). For instance, most information we come across in our daily lives is true. So when forced to guess, we often err on the side of believing.

Other shortcuts exist that encourage information — true or false — to find its way into our minds, research on human psychology shows. We take notice of information that is new, that fires up our emotions, that supports what we already believe and that we hear over and over.

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Most of the time, these shortcuts make us “super-efficient,” quickly leading us to the right answer, says cognitive psychologist Elizabeth Marsh of Duke University. But in fast-moving digital landscapes, those shortcuts are “going to get us in trouble,” she says.

How the various online platforms feed us information changes the game, as well. “We are not only contending with our own cognitive crutches as humans,” says Jevin West, a computational social scientist at the University of Washington in Seattle who cowrote the 2020 book Calling Bullshit: The Art of Skepticism in a Data-Driven World. “We’re also contending with a platform, and with algorithms and bots that know how to pierce into our cognitive frailties.” The goal, he says, is “to glue our eyeballs to those platforms.”

Here, scientists who study misinformation pull back the curtain on some false social media posts to show how bad information can creep into our minds.

Sharing what’s new

People take special notice of fresh information. “Novelty has an advantage in the information economy in terms of spreading farther, faster, deeper,” says information scientist Sinan Aral of MIT and author of the 2020 book The Hype Machine: How Social Media Disrupts Our Elections, Our Economy, and Our HealthAnd How We Must Adapt. Fresh intel can inform our beliefs, behaviors and predictions in powerful ways. In a study of Twitter behavior that spanned 10 years, Aral and his colleagues found more signs of surprise — an indicator that information was new — in people’s responses to false news stories than to true ones.

Sharing new tidbits can also provide a status boost, as any internet influencer knows. “We gain in status when we share novel information,” Aral says. “It makes us look like we’re in the know.”

New information becomes even more alluring in times of uncertainty, West says. That played out early in the COVID-19 pandemic, when researchers and physicians were scrambling to find life-saving treatments. Unproven methods — vitamins, garlic and hydroxychloroquine, among others — got lots of attention. “There were not a lot of answers on how to treat COVID early in the pandemic,” he says.

Misinformation: Natural “cure”

Expert’s review

This tweet provides unequivocal, confident certainty with “cure” and it appeals to people’s beliefs [in natural remedies] with “pawpaw tree” and “garlic.” The author understands well these tricks. The consumer will want to believe this, and … be in the know by seeing it before their friends receive it as a share.
Jevin West, University of Washington

Editor’s note: This box and those below show false statements found on social media or in the news. These examples, all misleading and untrue, show how misinformation can trick us.

Supports prior beliefs

Accepting information that’s consistent with what we already know to be true can feel like a safe bet. We tend to give that sort of message less scrutiny. “It’s more comfortable to find pieces of information that fit our narrative,” West says. “And when we are confronted with information that breaks that narrative, that’s incredibly uncomfortable.”

But this reliance on our stored knowledge can lead us astray. People are wrong about a lot of facts, easily confuse facts and opinions and claim to know facts that are impossible, as Marsh and her colleague Nadia Brashier of Harvard University wrote in 2020 in Annual Review of Psychology. And with so much information streaming in, it’s easy to find the material that fits with what you think you know. “To the extent that I want to believe X, I can go out there and find evidence for X,” Marsh says. “If I were an anti-vaxxer, it wouldn’t matter how many times you told me that vaccines are good, because it would be against my world identity,” she says.

Baseball legend and civil rights advocate Hank Aaron died on January 22 at age 86. Some people soon noted that he’d received a COVID-19 vaccine 17 days earlier. Anti-vaccine groups used his death to blame vaccines, with no evidence that the vaccine was involved. “It’s so opportunistic,” says global health researcher Tim Mackey of the University of California, San Diego.

Misinformation: Sports legend

Expert’s review

This one is very emotive. Most everyone knows Hank Aaron. [The post is] playing on [a] reaction of shock over his death (novel info) and then introducing misinformation that leads people to believe he died from the COVID-19 vaccine. The use of the [CBS Sports] link is compelling as it’s from a trusted news source, even though the link says nothing about Aaron dying from the vaccine. It almost makes him an unknowing martyr for the anti-vax movement. Aaron said he wanted to encourage vaccine uptake among African American people. His untimely death is instead used strategically to target this population.
— Tim Mackey, UC San Diego

Tugs on emotions

Playing on emotions is the “dirtiest, easiest trick,” West says.

Outrage, fear and disgust can capture a reader’s attention. That’s what turned up in Aral’s analyses of over 126,000 instances of rumors spreading through tweets, reported in 2018 in Science. False rumors were more likely to inspire disgust than true information, the researchers found.

“False news is shocking, surprising, blood-boiling, anger-inducing,” Aral says. “That shock and awe combines with novelty to really get false news spreading at a much faster rate than true news.” The presence of emotional language increases the spread of social media messages by about 20 percent for each emotion-triggering word, researchers at New York University reported in Proceedings of the National Academy of Sciences in 2017.

Along with message content, readers’ emotions matter, too. People who rely on emotions to assess a news story are more likely to be duped by fake news, misinformation scientist Cameron Martel of MIT and colleagues reported in 2020 in Cognitive Research: Principles and Implications.

Misinformation: Emotions

Expert’s review

[In studies], this headline was particularly evocative of both anger and anxiety, even relative to other false news headlines. I would guess that this has to do with the fact that the headline is tapping into both a common myth about (false) vaccine dangers, and focuses on potential harm to a vulnerable population (children).
— Cameron Martel, MIT

On repeat

Even the most outlandish idea begins to sound less wild the 10th time we hear it. That’s been the case since long before the internet existed. In a 1945 study, people were more inclined to believe rumors about wartime rationing that they had heard before rather than unfamiliar ones.

Many recent studies have found similar effects for repetition, a phenomenon sometimes called the “illusory truth effect.” Even when people know a statement is false, hearing it again and again gives it more weight, Marsh says. “Keep it simple. Say it over and over.”

There’s lots of repetition to be found on Twitter, where hashtags can draw many people into a conversation, Mackey says. On July 27, 2020, then-President Donald Trump tweeted a link to a video of a doctor making false claims that hydroxychloroquine can cure COVID-19. Similar tweets exploded soon after, jumping from an average of about 29,000 daily tweets to over a million just a day later, Mackey and his colleagues reported in the Lancet Digital Health in February. “It just takes one piece of misinformation for people to run with,” Mackey says.

Misinformation: Repetition

Expert’s review

[The tweet about Gates and Fauci] was a pretty common theme. Repetition for this one is all about building an online campaign. Essentially propagation serves two roles: (1) getting [the fake message] out there that people who are against use of hydroxychloroquine are involved in a conspiracy to keep the treatment out of people’s hands and (2) a campaign [to] force these public figures to actually get tested. — Tim Mackey, UC San Diego

Trustworthy journalism comes at a price.

Scientists and journalists share a core belief in questioning, observing and verifying to reach the truth. Science News reports on crucial research and discovery across science disciplines. We need your financial support to make it happen – every contribution makes a difference.

Questions or comments on this article? E-mail us at [email protected]

A version of this article appears in the May 8, 2021 issue of Science News.

Citations

S. Vosoughi, D. Roy and S. Aral. The spread of true and false news online. Science. Vol. 359, March 9, 2018, p. 1146. doi: 10.1126/science.aap9559.

N. Brashier and E. Marsh. Judging Truth. Annual Reviews of Psychology. Vol. 71, January, 2020, p. 499. doi: 10.1146/annurev-psych-010419-050807.

W. Brady et al. Emotion shapes the diffusion of moralized content in social networks. Proceedings of the National Academy of Sciences. Vol. 114, July 11, 2017, p. 7313. doi: 10.1073/pnas.1618923114.

C. Martel, G. Pennycook and D. G. Rand. Reliance on emotion promotes belief in fake news. Cognitive Research: Principles and Implications. Vol. 5, October 7, 2020. doi: 10.1186/s41235-020-00252-3.


Different types of hearing aids

Behind-the-ear (BTE) hearing aid

This aid hooks onto a person's ear. It consists of a hard plastic case, which sits behind the ear, connected to a small plastic, resin, acrylic or silicone earmold, which sits inside the outer ear. According to the U.K. National Health Service, it is the most common type of hearing aid. The behind-the-ear case contains the device's electronics, and sound travels from the hearing aid, via the earmold, into the ear.

Pros of BTE hearing aids:

&mdashA wide variety of people can use these aids, from young children to older adults, and they can assist with a broad spectrum of hearing loss, according to Hearing Aid UK, Ltd.

&mdashThey have larger batteries and so last longer.

&mdashThese aids tend to be cheaper than other models and are available in many styles and colors, with many functions.

Cons of BTE hearing aids:

&mdashBehind-the-ear hearing aids are not as discrete as other models, such as in-the-canal aids.

&mdashThe earmold can get blocked with ear wax and requires cleaning to avoid damage.

&mdashThese aids can make phone use awkward, because you have to hold your phone to the microphone rather than your ear canal.

Newer versions of this type of aid, called mini-BTE, have a smaller earmold, so that it does not block the outer ear completely. The smaller earmold means that fluid can drain in the ear.

In-the-ear (ITE) hearing aid

In-the-ear hearing aids sit entirely inside the outer ear. A hard plastic case still contains all the device's electronic components. There are two designs for this type of hearing aid: They can fill the ear bowl completely (called full shell) or partially (called half shell), depending on the wearer's preference.

Pros of ITE hearing aids:

&mdashThese aids are discrete, comfortable and small, according to Hearing Aid UK, Ltd.

&mdashThey are easy to insert into the ear

&mdashBecause they are in the ear, they are shielded from wind noise

Cons of ITE hearing aids:

In-the-canal (ITC) and completely-in-the-canal (CIC) hearing aids

In-the-canal hearing aids are custom molded to a person's ear canal. Some of them are almost invisible, being completely contained within the ear canal, while others are partially visible. Additionally, they have smaller batteries and less computing circuitry space (because they have to be as small as possible). Practically, this means that they cannot amplify as loudly and lack some of the signal processing functions that other types have.

Pros of ITC hearing aids:

&mdashPartially or completely invisible, depending on whether ITC or CIC, according to the AARP.

&mdashEasy to use a phone with these aids

Cons of ITC hearing aids:

&mdashBecause of their small size, they can be fiddly to insert and some can only be inserted by a professional.

&mdashThey tend to be expensive.

&mdashThey are small and so lack the battery and computing power of other types of hearing aids, and so may not be suitable for severe hearing loss.

How do smart hearing aids work?

In the same way that hearing aids benefited from the invention of the transmitter and transistor, they are also enjoying the current technological push in computer processing and big data. "Artificial intelligence has revolutionized the hearing aid industry and has brought a wide array of capabilities to the technology that helps you hear," said Hearing Industries Association, an American hearing aid lobby group.

For example, next-generation hearing aids, sometimes referred to as "smart" hearing aids, are able to connect to other internet-capable devices and remember a wearer's preferences. They can detect the wearer's environment and learn which noises to mute, like the clank of plates and background voices in a restaurant, and which to emphasize, such as the voice of another person sitting at the same table. By linking hearing aids to smartphones, apps are now also able to "clean" the sounds that the aid-wearer hears, making it easier to cut out noise, Healthy Hearing reported.

According to one article on a "smart" hearing aid from WIRED, linking to the internet and GPS allows the hearing aid to remember settings for different locations and automatically adjust its own levels. These levels could even be transmitted to a cloud-based service, said an article from the Institution of Engineering and Technology, with pre-set levels for different environments.

Current hearing aids are already able to stream music and audiobooks.

How do I know if I need a hearing aid?

According to the Mayo Clinic, signs of hearing loss include:

&mdashStruggling to understand works, especially when there is noise in the background

&mdashYou find yourself constantly asking people to speak more loudly or to repeat themselves

&mdashDifficult hearing consonants

&mdashPlaying the TV or music at a volume that other people find too loud

&mdashWithdrawing from conversations because you struggle to understand what people are saying

If you suspect that you may be losing your hearing, which happens naturally with age, or if you have a sudden loss of hearing in one or both ears, see a doctor. Hearing tests are also available online.

How do I get a hearing aid?

To rule out other causes of your hearing loss &mdash such as an infection, ear wax, infection or rarely a tumor &mdash the FDA recommends people get a medical examination by either a general practitioner or, preferrably, an ear, nose and throat doctor. The FDA strongly recommends a medical examination for anyone under age 18: "For hearing aid consumers younger than 18 years of age, the FDA will continue to enforce the medical evaluation requirement to rule out medical causes of hearing loss prior to buying hearing aids," the FDA said in a statement.

However, if you are 18 years or older and don't think you need a medical evaluation, a hearing test is a must. Several companies also offer hearing tests online. In addition, a general doctor will be able to refer you to an audiologist, which is a hearing specialist, who will perform a hearing test. This test measures how loud a sound needs to be for you to hear it and how clear it is, according to Harvard Medical School. "People with normal hearing can hear sounds less than 25 decibels (dB). If the softest sounds you can hear are 30 dB or louder, you may be missing a significant amount of what is said to you and are probably a candidate for a hearing aid."

The audiologist will be able to guide you in which hearing aid would suit you best.

History of hearing aids

Even before the advent of modern electronics, people who were partially deaf or hard of hearing used tools to amplify sounds. The simplest tool, the ear trumpet or horn, was a funnel-shaped implement that people inserted into their ears to improve their ability to hear. The large mouth of the funnel collected sound waves from the environment and channelled them into a person's ear.

French Jesuit priest and mathematician Jean Leurechon was the first person to describe the ear trumpet in 1634 in his work "Recreations Mathématiques," wrote Max Valentinuzzi, a professor emeritus with the Universidad Nacional de Tucumán in Argentina, in a paper published in journal IEEE. By the end of the 1700s, ear trumpets were commonplace, according to Valentinuzzi.

But the invention of the telephone presaged the hearing aid revolution, Valentinuzzi continued. In 1870, Thomas Edison developed the carbon transmitter for his telephone, which amplified electric signals and increased the resulting sound's volume.

In 1898, American electrical engineer Miller Reese Hutchison used a carbon transmitter to build a portable amplifier. His invention &ndash&ndash "the akouphone" &ndash&ndash was the first dedicated electric hearing aid.

By 1920, said the Kent State University Hearing Aid Museum, hearing aid makers were experimenting with vacuum tubes instead of carbon transmitters as they were able to achieve a greater amplification. However, they were bulky and unwieldy.

The era of small, discreet hearing aids began in 1948 when Bell Telephone Laboratories invented the transistor, Valentinuzzi wrote. The transistor, which is at the heart of modern electronics, allowed hearing aids to control the flow of electrical current and its subsequent volume. They were also much smaller than previous models, and a person could wear the device in their ear.

In fact, after World War II, hearing aids became a test ground for the miniaturization of electronics. Their users became the first consumer market for printed circuits, transistors, and integrated circuits, wrote Mara Mills, an associate professor of media, communication, and culture at New York University.

"The new hearing aids were so popular and successful that more than 200,000 transistor hearing aids were sold in 1953 alone, eclipsing the sale of vacuum tube models," Max Valentinuzzi wrote in his article.

The circuitry in today's hearing aids is much more sophisticated, Mills wrote in her article, and able to amplify certain frequencies while cutting out others that might be part of background noise.


Transduction of Light

Light is tranduced in rods and cones visual information is processed in the retina before entering the brain.

Learning Objectives

Explain retinal processing and the process of transduction of light

Key Takeaways

Key Points

  • When light hits the photoreceptor, the retinal changes shape, which activates the photopigment rhodoposin.
  • Primates have full color vision because of the three- cone (trichromatic) system color is a result of the ratio of activity of the three types of cones.
  • There are three types of cones with different photopsins: S cones respond to short waves M cones respond to medium waves L cones respond to light to long waves.
  • If light is not present, neurons are inhibited by rods and cones once light is introduced, rods and cones are hyperpolarized, which activates the neurons.
  • Activated neurons stimulate ganglion cells, which send action potentials via the optic nerve.
  • Horizontal cells can create lateral inhibition, which enhances light and dark contrast in images.

Key Terms

  • tonic activity: when photoreceptors become slightly active even when not stimulated by light
  • rhodopsin: a light-sensitive pigment in the rod cells of the retina it consists of an opsin protein bound to the carotenoid retinal

Transduction of Light

The rods and cones are the site of transduction of light into a neural signal. Both rods and cones contain photopigments, which are pigments that undergo a chemical change when they absorb light. In vertebrates, the main photopigment, rhodopsin, has two main parts: an opsin, which is a membrane protein (in the form of a cluster of α-helices that span the membrane) and retinal, a molecule that absorbs light. When light hits a photoreceptor, it causes a shape change in the retinal, altering its structure from a bent (cis) form of the molecule to its linear (trans) isomer. This isomerization of retinal activates the rhodopsin, starting a cascade of events that ends with the closing of Na + channels in the membrane of the photoreceptor. Thus, unlike most other sensory neurons (which become depolarized by exposure to a stimulus), visual receptors become hyperpolarized and are driven away from the threshold.

Hyperpolarized visual receptors: When light strikes rhodopsin, the G-protein transducin is activated, which in turn activates phosphodiesterase. Phosphodiesterase converts cGMP to GMP, thereby closing sodium channels. As a result, the membrane becomes hyperpolarized. The hyperpolarized membrane does not release glutamate to the bipolar cell.

Rhodopsin: (a) Rhodopsin, the photoreceptor in vertebrates, has two parts: the trans-membrane protein opsin and retinal. When light strikes the retinal, it changes shape from (b) a cis to a trans form. The signal is passed to a G-protein called transducin, triggering a series of downstream events.

Trichromatic Coding

There are three types of cones (with different photopsins) that differ in the wavelength to which they are most responsive. Some cones are maximally responsive to short light waves of 420 nm they are called S cones (“S” for “short”). Other cones (M cones, for “medium”) respond maximally to waves of 530 nm. A third group (L cones, or “long” cones) responds maximally to light of longer wavelengths at 560 nm. With only one type of cone, color vision would not be possible a two-cone (dichromatic) system has limitations. Primates use a three-cone (trichromatic) system, resulting in full color vision.

Rod and cone cells: Human rod cells and the different types of cone cells each have an optimal wavelength. However, there is considerable overlap in the wavelengths of light detected.

The color we perceive is a result of the ratio of activity of our three types of cones. The colors of the visual spectrum, running from long-wavelength light to short are:

  • red (700 nm)
  • orange (600 nm)
  • yellow (565 nm)
  • green (497 nm)
  • blue (470 nm)
  • indigo (450 nm)
  • violet (425 nm).

Humans have very sensitive perception of color and can distinguish about 500 levels of brightness, 200 different hues, and 20 steps of saturation in all, about 2 million distinct colors.

Retinal Processing

Visual signals leave the cones and rods, travel to the bipolar cells, and then to ganglion cells. A large degree of processing of visual information occurs in the retina itself, before visual information is sent to the brain.

Photoreceptors in the retina continuously undergo tonic activity. That is, they are always slightly active even when not stimulated by light. In neurons that exhibit tonic activity, the absence of stimuli maintains a firing rate at an equilibrium while some stimuli increase firing rate from the baseline, other stimuli decrease firing rate. In the absence of light, the bipolar neurons that connect rods and cones to ganglion cells are continuously and actively inhibited by the rods and cones. Exposure of the retina to light hyperpolarizes the rods and cones, removing the inhibition of their bipolar cells. The now-active bipolar cells in turn stimulate the ganglion cells, which send action potentials along their axons (which leave the eye as the optic nerve). Thus, the visual system relies on changein retinal activity, rather than the absence or presence of activity, to encode visual signals for the brain. Sometimes horizontal cells carry signals from one rod or cone to other photoreceptors and to several bipolar cells. When a rod or cone stimulates a horizontal cell, the horizontal cell inhibits more-distant photoreceptors and bipolar cells, creating lateral inhibition. This inhibition sharpens edges and enhances contrast in the images by making regions receiving light appear lighter and dark surroundings appear darker. Amacrine cells can distribute information from one bipolar cell to many ganglion cells.


What Is It Like to Hear With A Cochlear Implant?

One summer, Allyson was in a car accident that totaled her car and left her in the hospital. After months of rehabilitation and recovery from her visible injuries, she woke up one morning and knew her life was different. Her dog Maddie jumped, started barking, and ran across the room, but Allyson heard nothing. She picked up the phone and listened for a dial tone, but again, nothing. Though Allyson had grown up with partial hearing and used hearing aids most of her life, her car accident had sent her into a life of complete silence. Allyson had lost her hearing entirely.

Learn more about Allyson’s experience, and how research from Rene Gifford’s lab enabled her to continue to pursue a career in audiology, in this video produced by Science Friday and Howard Hughes Medical Institute:

Next Generation Science Standards

This resource can be used to make progress towards the following performance expectations:

MS-PS4-2
Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

MS-PS4-3
Integrate qualitative scientific and technical information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals.

Common Core State Standards

ELA RST.6-8.9
Compare and contrast the information gained from experiments, simulations, video, or multimedia sources with that gained from reading a text on the same topic. (MS-PS4-3)

MATH.CONTENT.6.SP.B.4
Display numerical data in plots on a number line, including dot plots, histograms, and box plots.

MATH.CONTENT.6.SP.B.5
Summarize numerical data sets in relation to their context

Many thanks to Kristen D’Onofrio and Rene Gifford of the Cochlear Implant Research Laboratory in the Department of Hearing and Speech Sciences at Vanderbilt University for their assistance with the simulations and research shared in this resource.

Teachers who field tested this resource had the following advice for teachers adopting this resource:
Lora from Texas said: The video was very well done, loved the comparison, opportunity to graph results and pre/post test and reflection questions. I recommend copying ear diagrams two photos per page so students can easily compare and draw pathways. You can also copy response questions into Google doc and walk students through intro and conclusions instead of it being self-paced.

This article was revised 4/21/2017 to correctly indicate that the filters that have been applied to the hearing aid simulations are low pass filters, which remove all frequencies above the indicated frequency, not below.


Mechanism of Action of Gymnemic Acids

Gymnemic acid formulations have also been found useful against obesity, according to recent reports [10]. This is attributed to the ability of gymnemic acids to delay the glucose absorption in the blood. The atomic arrangement of gymnemic acid molecules is similar to that of glucose molecules. These molecules fill the receptor locations on the taste buds thereby preventing its activation by sugar molecules present in the food, thereby curbing the sugar craving. Similarly, Gymnemic acid molecules fill the receptor location in the absorptive external layers of the intestine thereby preventing the sugar molecules absorption by the intestine, which results in low blood sugar level [11].

G. sylvestre leaves have been found to cause hypoglycemia in laboratory animals and have found a use in herbal medicine to help treat adult onset diabetes mellitus (NIDDM). When Gymnema leaf extract is administered to a diabetic patient, there is stimulation of the pancreas by virtue of which there is an increase in insulin release [12]. These compounds have also been found to increase fecal excretion of cholesterol [13], but further studies to prove clinical significance in treating hypercholesterolemia (high serum cholesterol) are required. Other uses for Gymnema leaf extract are its ability to act as a laxative, diuretic, and cough suppressant. These other actions would be considered adverse reactions when Gymnema is used for its glucose lowering effect in diabetes.

Gymnema leaf extract, notably the peptide &lsquoGurmarin&rsquo, has been found to interfere with the ability of the taste buds on the tongue to taste sweet and bitter. Gymnemic acid has a similar effect. It is believed that by inhibiting the sweet taste sensation, people taking it will limit their intake of sweet foods, and this activity may be partially responsible for its hypoglycemic effect [14].

There are some possible mechanisms by which the leaves and especially Gymnemic acids from G. sylvestre exert its hypoglycemic effects are: 1) it increases secretion of insulin, 2) it promotes regeneration of islet cells, 3) it increases utilization of glucose: it is shown to increase the activities of enzymes responsible for utilization of glucose by insulin-dependant pathways, an increase in phosphorylase activity, decrease in gluconeogenic enzymes and sorbitol dehydrogenase, and 4) it causes inhibition of glucose absorption from intestine.

The gymnemic acid components are believed to block the absorption of glucose in the small intestine, the exact action being unknown. It could be involve one or more mechanisms .

The leaves are also noted for lowering serum cholesterol and triglycerides. The primary chemical constituents of Gymnema include gymnemic acid, tartaric acid, gurmarin, calcium oxalate, glucose, stigmasterol, betaine, and choline. While the water-soluble acidic fractions reportedly provide the hypoglycemic action, it is not yet clear what specific constituent in the leaves is responsible for the same. Some researchers have suggested gymnemic acid as one possible candidate, although further research is needed. Both gurmarin (another constituent of the leaves) and gymnemic acid have been shown to block sweet taste in humans. The major constituents of the plant material 3B glucuronides of different acetylated gymnemagenins, gymnemic acid a complex mixture of at least 9 closely related acidic glucosides [17&ndash19].

Chaudhari,C, et al, (1996). The taste of monosodium glutamate: membrane receptors in taste buds.J.Neuroscience.16:3817-3826.

Kurihara,K and Kashiwayanagi, M. (1998). Introductory remarks on umami taste. Annals NY AcadSci.855:393-397.

Nelson, G. et al (2002). An amino-acid taste receptor. Nature 416:199-204. Purves,D, et al. (2008). Neuroscience 4 ed. Sunderland,MA:Sinauer Associates,Inc.

Smith, David and Margolskee, Robert (2001). Making sense of taste. Scientific American 284:32-39.

Reinberger, Stefanie. (2006) Bitter could be better. Scientific American 294:56-61

PBS has an apple sweetness lab based on Michael Pollan&rsquos book Botany of Desire http://www.pbs.org/thebotanyofdesire/apple-sweetness.php

Schroeder,J and Flanery-Schroeder,E (2005) Use of the Herb Gymnema sylvestre to Illustrate the Principles of Gustatory Sensation: an Undergraduate Neuroscience Laboratory Exercise. The Journal of Undergraduate Neuroscience Education (JUNE) 3(2):A59-62

Adapted from Schroeder,J and Flanery-Schroeder,E (2005) Use of the Herb Gymnema sylvestre to Illustrate the Principles of Gustatory Sensation: an Undergraduate Neuroscience Laboratory Exercise. The Journal of Undergraduate Neuroscience Education (JUNE) 3(2):A59-62 and from a lab by David Guay.


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Watch the video: Fake signals indicators u0026 This is the solution!! iq option strategy 2017 (August 2022).