Archive for the ‘Binaural’ category

Hearing with Only One Ear (Unilateral Hearing Loss)

July 27th, 2011

By: Joan D’Alessandro, Au.D.
Doctor of Audiology
Advanced Hearing & Balance Care
30 South Valley Rd., Ste. 208
Paoli, PA 19301
(610) 296-5857
www.hearingcare4u.com

Hearing loss in one ear can result from several disorders or injuries:

  • Bacterial  infections
  • Head injury
  • Vascular (blood supply) problem
  • Meniere’s disease
  • Viral infection (herpes)
  • Acoustic or 8th nerve tumor
  • Acoustic trauma (sudden loud noise to one ear)

Patients who suffer a severe to profound hearing loss in one ear report no comprehension difficulty in quiet, one-one-one conversations.  However, understanding conversation in less than ideal listening situations is severely compromised.  These include noisy areas such as restaurants,  group conversations and reverberant areas such as churches, gyms, and indoor swimming pools.

Why are these areas so challenging for those with unilateral deafness?  Your ears individually and collectively gather acoustic information and relay those signals to the auditory reception centers in your brain.  With only one ear collecting information, the auditory centers are starved for the complete acoustic picture normally provided by two ears.  When this information is lacking, a number of things  happen that impair your ability to organize and make sense of speech.

Joan D'Alessandro, Au.D. - Doctor of Audiology, Paoli, PennsylvaniaHead Shadow Effect

When a sound occurs toward the deaf ear, the arrival of that sound at the hearing ear is partially blocked by your head, commonly known as the head shadow effect.  The sounds most easily blocked are the higher pitches which are absolutely  necessary for accurate perception of the voiceless consonant sounds of speech, the s,c,f,t,p,ch and  sh sounds.  These consonants allow us to tell the difference between words like teach versus feast and distillery versus facility. This word discrimination ability is compromised by hearing with only one ear because of the head shadow effect.

Localization Ability

Your brain needs well-balanced sound information from both ears for you to be able to easily pick out the direction from which a sound originates.  Both a sound’s time of arrival (it arrives a few milliseconds faster at the ear closest to the sound) and its intensity or loudness (louder for the ear closest to the sound) are cues that your brain uses to locate the source of a sound.  When you have only one ear, all sounds seem to be coming from the side of the  good ear, even when originating from the bad ear side.  So someone with hearing in only one ear lacks the instantaneous locating cues of time and intensity.  If someone calls your name outdoors, you have to turn your head around to locate the source and it may take several repetitions to accurately pinpoint the source.

Sound Summation and Noise Squelch

To your brain, one ear + one ear = three!  A sound which is barely audible at 20 feet away with only one ear, is easily audible at 30 feet when two ears are listening.  This is called the binaural summation effect and is the result of the two hearing nerves crossing many hundreds of times before the information reaches the cortex.  This crossing or decussation results in the enhancement of sound, so softer sounds become audible.

In addition, this neural sharing contributes to an advantage, known as binaural squelch, when listening in background noise.  This ‘squelch’ provides 3 decibels more signal than noise, also known as the signal –to- noise ratio or SNR.  Even though three  decibels may not seem like much, the decibel is a logarithmic function much like the Richter scale for earthquake measurement.   For every 3 decibels, sound power actually doubles. So three decibels extra is a significant amount and allows for easier understanding in noisy situations.

Solutions for Those with Only One Hearing Ear

The traditional hearing aid solution for unilateral hearing loss has been the use of a CROS hearing aid. The acronym stands for Contralateral Routing of Sound and employs a unit on the dead ear which contains a microphone to pick up sounds arriving on that dead side.  Those sounds are then transmitted wirelessly to a receiver unit on the good side. The sounds from the dead side are then routed into the good ear.

This CROS type aid prevents the head shadow effect but does nothing for localization ability and does not provide binaural summation or squelch.

If the hearing loss is in the  severe category, a traditional hearing aid either in a behind-the-ear(BTE) or in-the-ear style  can be fit.  As with all hearing aids fittings there is an accommodation period during which the patient learns to use the acoustic information from the damaged ear.  The sooner the fitting is done, the more likely the patient will be a successful hearing aid user.

A fairly recent surgical solution for single-sided deafness (SSD) is the implantation of a BAHA or Bone-Anchored Hearing Aid.  This surgical implant uses bone conduction to send sounds from the bad ear side to the good ear via an implant with a microprocessor that adheres to a magnet under your scalp.  The processor is detachable for showering, etc., and is easily hidden underneath your hair.  Again, the BAHA does not accomplish true binaural hearing but does lessen the head shadow effect and some recipients do notice improved localization ability after use of the BAHA for some time.

Our brains are wired to receive information from both ears. Loss of hearing in one ear is a significant handicap with which many people cope through the use of CROS type hearing aids, BAHA implant and positioning themselves  to maximize the best sound reception to the hearing ear.

Now Hear this…. Are You at Risk for a Hearing Loss?

June 18th, 2010

By: Bettie Borton, Au.D., FAAA
Doctor of Audiology
Doctors Hearing Clinic
7025 Halcyon Park, Suite A
Montgomery, AL 36117
(334) 396-1635
www.doctorshearingclinic.com

Did you know hearing loss…

  • Is the third most prevalent chronic health condition in America, behind high blood pressure and arthritis?
  • Affects 36 million Americans (about 17% of adults)?
  • Is more common in men than women?
  • Costs our economy billions of dollars in lost wages and hidden costs annually?

Is not being adequately identified by healthcare professionals? Only 38 percent of adults ages 70 years and older and only 29 percent of adults ages 20 to 69 have had their hearing tested within the last 5 years!

Do you or someone you love have a hearing loss? If so, you’re not alone. Almost 20% of adults in the United States will develop hearing loss during the course of their lives, and if undiagnosed and untreated, its affects can be devastating. Impaired hearing can have a profound impact on emotional, physical, economic, and social well-being.  People with hearing loss have documented decrease in quality of life, reporting symptoms of depression, dissatisfaction with life, reduced functional health, and social isolation. Statistically, they have lower income levels, and frequently complain of frustration in relationships and various communicative situations, as well as inability to enjoy social situations, and fatigue. Despite the fact that most people with hearing loss can be helped with today’s state of the art amplification, many never seek help, or resist the use hearing aids or other assistive listening technologies.

The causes of hearing loss are varied and resultant impact on auditory capability may range from mild to pronounced. Sometimes the cause or etiology, such as wax build up in the external ear canal or an ear infection, is readily apparent. In other instances, the cause of hearing loss may be more obscure. Decreased hearing is often called “the invisible handicap”. Because hearing impairment (especially loss related to aging) often presents very gradually, those with significant hearing impairment can be unaware of their loss. Family members, significant others, co-workers and friends are frequently the first to notice communication problems related to decreased hearing sensitivity.

Given that 36 million Americans are faced with this “invisible handicap” what kinds of risk factors increase the likelihood that someone will develop hearing loss? Why do some people develop hearing loss and while others do not? Some risk factors are obvious, but others are much more obscure.

Perhaps the most widely recognized risk factor is aging. Presbycusis, or the loss of hearing that gradually occurs as we grow older, is a familiar scenario for those of us with older family members. In fact, about 30-35 percent of adults between the ages of 65 and 75 years have a hearing loss, while an estimated 40-50 percent of people 75 and older have a hearing impairment.

Loss associated with presbycusis is usually greater for high-pitched sounds, resulting in the frequent comment “I can hear people talking, but can’t understand them clearly”. It is most commonly binaural (in both ears), affecting the ears equally. Because this type of loss in hearing sensitivity is so gradual, people who have presbycusis frequently lose their frame of reference for normal loudness of sounds, and often do not realize that their hearing acuity is diminishing.

The resultant relationship dynamic is frequently the subject of jokes – “My husband suffers from ‘selective’ hearing and he’s driving me crazy”! In reality, however, hearing impairment is no laughing matter and can take quite a toll on communication with significant others. Research indicates that for couples where one person has unaddressed hearing loss, the divorce rate is actually significantly higher.

Most people would agree that we now live in a very noisy world. Noise levels for rock concerts, radios, motorcycles, traffic, industrial and lawn equipment, and even our personal listening devices constantly bombard our auditory system. It is not surprising that noise exposure is another one of the most frequently cited risk factors for hearing loss, and now rivals aging as the number one cause of hearing loss in this country.  Noise from occupational, recreational and sporting activities all pose significant hazards to hearing in the United States today. Firearm use is one of the biggest culprits in our area of the country. A single shot from a shotgun, experienced at close range, can permanently damage hearing.  Repeated exposures to loud machinery in the work place or as part of yard maintenance or recreational experience may, over an extended period of time, present a serious risk to hearing. Even something as seemingly benign as blow dryers for styling hair put hearing at risk.

Consider the noise levels for such activities as NASCAR, jet ski and power boat usage, and lawn equipment. The cumulative effects of these noise hazards and many others pose a serious risk for hearing. Noise exposure risk is a time weighted function – in other words, the longer the exposure time, the greater the risk, and lower the loudness level required to cause damage. According to the National Institute on Deafness and Other Communication Disorders (NIDCD), 10 million Americans have already suffered irreversible hearing damage from noise, and 30 million more are exposed to dangerous noise levels each day. A one-time exposure to hazardous noise resultant from gunfire or a rock concert, no matter how brief the time, of 120 dB or more can leave hearing permanently impaired. Prolonged exposure to only 85 dB (which can be generated by a commonly used appliance such as a blow dryer or hand held power tool) can do the same. 

Children and young adults are bombarded with potentially damaging noise exposure, most of which is easy to overlook. Most people intuitively recognize that “boom boxes”  IPODS, and other personal listening devices, if played too loudly, constitute a risk to hearing. However, consider the noise levels inherent to playing in a school band or orchestra. Students engaged in this commonplace activity spend hours practice in noisy environments within the context of their academic activities, yet many of them are not wearing appropriate ear protection, nor are schools effectively addressing this problem. To complicate matters, for reasons that are not fully understood some people are more susceptible to noise exposure than others.  As an example, research indicates that those with blue eyes are more prone to noise exposure than those with darker eye color!

Aging and noise exposure are two rather obvious risk factors for hearing loss, but there are many other factors that are more insidious. Studies suggest that there is a strong genetic component inherent to hearing loss, both for childhood deafness as well as presbycusic loss. If your parent or grandparent had hearing loss, your risk factor for developing a similar impairment may increase. If you had a relative who was hearing impaired from birth, family members of child bearing age need to be mindful of this risk factor, and be particularly vigilant with regard to insuring that the newest members of the family are effectively screened at birth for hearing sensitivity.

Various diseases of the ear certainly pose risk to hearing sensitivity. Ear infection, otosclerosis (a bony growth in the middle ear cavity), Meniere’s Disease, acoustic neuroma (a tumor on the auditory nerve), and a host of other maladies are obvious risk factors for hearing loss. But did you know that hearing loss is about twice as common in adults with diabetes compared to those who do not have the disease, according to a new study funded by the National Institutes of Health (NIH)? Visual deficits have long been associated with diabetes, but hearing loss is an under-recognized complication. Because of the strong correlation between diabetes and hearing loss, The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), recently suggested that people with diabetes should consider having their hearing tested.

Use of common drugs such as antibiotics, aspirin, diuretics and chemotherapy can cause hearing loss. Typically, hearing loss from ototoxic drugs is high frequency, which often results in the hearing impairment less obvious to those it affects. All radiation and chemotherapy patients should insist on baseline hearing assessments before, during, and following their course of treatment to insure that auditory effects of ototoxic interventional strategies are carefully monitored and treated.

Race and gender also play a role in hearing loss risk factor determination. Researchers now know that compared to women, men are five and one half times more likely to have hearing loss. White and Mexican American men have a higher incidence of both high-frequency hearing loss and hearing loss in both ears than blacks, who were 70 percent less likely than white participants to present with hearing loss.

With the dramatic increase in airbag use, motor vehicle accidents (MVA’s) are common culprits for increased risk of hearing loss. In fact, 17% of those involved in MVA’s with airbag deployment will have permanent loss of hearing as a result. Other insidious risk factors for hearing loss include smoking and cardiovascular disease. The incidence of hearing loss is significantly more pronounced among smokers, as well as those with any type of cardiovascular disease.

Many healthcare professionals simply don’t make these associations, and as a result, do not refer patients for hearing evaluation as often as risk factors might dictate. So, the message is be aware, and be proactive in assessing your risk, or that of your loved one, for hearing loss. For a comprehensive audiometric evaluation, see a Board Certified Doctor of Audiology. If you’ve never had a baseline audiogram, it’s certainly in your best interest to do so. Only 38 percent of adults ages 70 years and older and only 29 percent of adults ages 20 to 69 have had their hearing tested within the last 5 years.   If you’re over 65, hearing evaluation each year by a Board Certified Audiologist should become part of your annual medical maintenance program.
(Sources: BHI, NIDCD, ABA)

Dr. Bettie Borton is a Board Certified Doctor of Audiology, and a nationally recognized expert in hearing healthcare. She has more than 30 years’ experience diagnosing and treating hearing impairment in children and adults. Dr. Borton has served as the President of the Alabama Academy of Audiology, National Chair of the American Board of Audiology, and currently serves on the National Board of Directors for the American Academy of Audiology.