Can You Hear Me Now?

Made in Minnesota Minnesota is home of several companies that specialize in hearing research and designing personal hearing devices. Starkey Laboratories, based in Eden Prairie, has a new product line called the Destiny Series, which uses nanotechnology instead of mechanical switching to activate features different features. GN ReSound, a hearing device company with North American headquarters in Bloomington, offers the ReSound Metrix, which focuses on reducing background noises such as echoes and wind.

Can you hear me now? That ubiquitous refrain makes a great pitch for a cell phone service provider because almost everyone has experienced the crackly conversations and misheard words that come with poor cell phone reception. However, unlike difficult-to-understand cell phone discourse, a person with hearing loss may not be aware of the parts of the conversation that he or she is missing.

Hearing is a complex process that converts sound waves into electrical signals that are interpreted by the brain. The outer ear gathers or funnels sounds into the middle ear. There it vibrates a thin, transparent membrane called the eardrum, which separates the external ear from the middle ear. Small bones in the inner ear, called ossicles—the hammer, the anvil, and the stirrup—pick up the vibrations from the eardrum and send them through ear fluid to the cochlea, a spiral-shaped cavity that looks like a snail shell, which contains tiny hair cells. The movement of the tops of the hair cells stimulates nerve impulses, which are then sent to the brain.

Cell phones are notorious for abrupt dropped calls when the reception cuts out. We lose our ability to hear somewhat more gradually—over perhaps 25 to 30 years. According to the Hearing Loss Association of America, there are four types of hearing loss:

Sensorineural or nerve-related hearing loss in the inner ear can be caused by such as aging, infections, trauma, heredity, and exposure to loud noises. Hearing loss caused by these factors tends to be treatable with hearing devices.

Conductive hearing loss is due to actual blockage of the outer or middle ear, preventing sound from entering the inner ear. Causes include earwax build-up, a punctured eardrum, heredity, or infections, and can be treated medically or with surgery.

Mixed hearing loss is a combination of both sensorineural and conductive losses.

Central hearing loss is a much rarer phenomenon. Here, sound is able to pass through the ear, but somewhere along the nerve path to the brain, or in the brain itself, the signal becomes garbled.

Lend Me Your Ears

Hearing aids could be the solution for 95 percent of the 28 million Americans with hearing loss, according to the Hearing Loss Association. (Medical and surgical options are available for the other 5  percent.) However, the association notes that only 22 percent of those with hearing loss currently use hearing aids.

As the ability to hear decreases, many people have no idea what they aren’t hearing. A 2003 study from the University of Florida found that people with hearing loss denied the problems it caused. “There’s an expression by a famous audiologist, Mark Ross, that when someone in the family has a hearing loss, the entire family has a hearing problem,” says Patricia Kricos, the University of Florida professor who led the research. “That is so true, because it affects every member of the family, not just the person who’s hard of hearing.”

Notes Dr. Kurt Pfaff, a Minnesota licensed audiologist, “We’re all going to have hearing loss at some point in our life. It’s kind of like eyeglasses. When you turn 40, you start using glasses to read better. It’s the same kind of issue. But some people lose it to a greater degree, sooner. Others hold on for a longer period before it starts to diminish.”

Protecting yourself from damaging sound is the best option, because once the damage occurs there is no way to reverse it. Hearing tests can establish a benchmark and help shape a treatment plan. The main test used is an audiogram, which measures responses to low, middle, and high sound frequencies. A newer test called the otoacoustic emissions test measures the integrity of the hair cells that vibrate to stimulate nerve impulses in the inner ear.