Understanding Hearing Loss, Causes, Types & Symptoms.
More than 28 million Americans suffer from a significant loss of hearing. Almost half are under the age of 65 and 54% of the population over the age of 65 suffer from hearing loss. Hearing loss is the third most common medical condition in our adult population, following only high blood pressure and arthritis. On average, once a person determines that they have a hearing loss, they wait over seven years before seeking assistance.
The impact of a hearing loss can be far reaching and involve many aspects of one's life. Hearing impaired individuals may have difficulty localizing sounds, understanding speech in busy environments, and participating in everyday normal conversations. This can lead to social isolation, confusion, frustration, tension, anger, stress and depression. Recent studies also indicate that untreated hearing loss negatively affects one's overall health, quality of life and happiness.
Causes of Adult Hearing Loss.
With the advancement of medical science over the last few decades, one would think that we would be abe to explain the reasons for each individual's hearing loss, unfortunately this is not the case. There are basically two types of hearing loss, Sensorineural and Conductive.
Sensorineural Hearing Loss is the most common type of hearing loss. Previously this type of hearing loss was referred to as Nerve Deafness or Nerve Damage. With this type of hearing loss the hair cells in the inner ear (Cochlea) have become damaged or less effective. Sensorinerual hearing loss is almost never correctable thru medical or surgical means. There are numerous reasons for this condition to occur, but the most common are:
- Aging or Presbycusis, the naturally declining hearing due to the aging process,
- Exposure to loud, sudden or prolonged noise,
- Certain medicines,
- Injury or Infection.
Conductive Hearing Loss occurs when there is a problem in the outer ear or the middle ear, such as ear wax, fluid behind the eardrum, or middle ear infection. Many times this type of hearing loss may be corrected by medical or surgical treatments.
Symptoms of Hearing Loss.
If you recognize any of the following symptoms of hearing loss, please contact one of our offices or your personal physician to have your hearing professionally evaluated. If you are not close to a Manan Hearing Care Center please contact us at
1-800-416-2434 for a referral to a competent hearing professional in your area.
Do you have any of the following symptoms?
- Have to strain to hear conversations,
- Have to watch other people's faces for speech cues,
- Need to ask people to repeat,
- Misunderstand what people are saying,
- Turn the television or radio up,
- Feel that people are mumbling,
- Hear better on the phone with one ear than the other.
The fitting of hearing aids begins with audiometry or the measurement of hearing. Commonly, a pure-tone-hearing test is used to obtain hearing thresholds at a number of frequencies (e.g., 250, 500, 1000, 1500, 2000, 3000, 4000, 6000, and 8000 Hz). The results are normally plotted and reported in the standard form of an audiogram. Figure 2 shows an example of an audiogram. Based on the audiogram, the hearing professional can determine how much speech information is lost as a result of hearing loss. The audiogram can also be used to suggest how hearing-aid amplification should be applied at different frequencies to maximize the recovery of the lost speech information.
Figure 2. Audiogram showing the hearing threshold (red curve) of an impaired ear. The gray area marks where the energy of conversational speech could spread over intensity and frequency. The portion of the area above the hearing threshold (i.e., the red curve) is inaudible to the ear, resulting in a reduced speech-intelligence index (SII) of 0.55. The yellow area marks where the energy of a conversational speech could spread over intensity and frequency AFTER amplification. The amplification moves a significant portion of the inaudible speech energy above threshold, improving the SII to 0.78.
Call Manan Hearing for a FREE hearing evaluation today. 1-800-416-2434.
More about Hearing Loss:
Conductive losses are caused by problems with the outer or middle ear (see Fig. 1 for the structures of outer, middle, and inner ear). The reasons can be buildup of wax or fluid, puncture of eardrum, middle-ear infection, and diseases that immobilize the bones of the middle ear, which lead to attenuation in the transmission of the signals. This type of hearing loss typically reduces sensitivity but not the dynamic range. With sufficient amplification that gives equal boosts to soft as well as intense sounds, the patient's perception of the acoustic world can be restored close to normal. For these patients, hearing aids are an effective remedy. It should be noted that, in many cases, these conditions can be corrected medically without the use of hearing aids.
Sensorineural hearing losses can be caused by problems with the cochlea or the auditory nerve, as a result of exposure to noise and toxins, diseases, or simply aging. Hearing losses with cochlear origin exhibit a number of distinct characteristics. First, they typically occur at high frequencies, with low-frequency hearing affected to a less degree, or even being normal. Second, in the frequency region of significant loss (such as at high frequencies), the loss of sensitivity is mostly for soft sounds; loudness perception of intense sounds remains largely normal. As a result, the range of sounds that are perceptible, the dynamic range, is reduced. Finally, in a noisy environment, patients with such losses have difficulty understanding speech, even when the speech signal is clearly audible. This effect on speech perception is probably the most damaging, and it is also a defect that is most difficult to correct, with hearing aids, or any other means.
To understand the symptoms of sensorineural hearing loss, it would be helpful to look at the functions of the key sensory cells of the auditory system, and, in particular, what happens to these sensory cells in a damaged cochlea. After the acoustic signal is converted into mechanic vibration by the middle ear, the middle-ear bone structure drives the energy into the cochlea via the oval window, to create a localized vibration on the basilar membrane (BM). Along the length of the BM in the cochlea sit three rows of outer hair cells and one row of inner hair cells. In responding to an incoming tone, the basilar membrane will vibrate, with the location of the peak vibration depending on the frequency. In this mapping from signal frequency to BM place, the higher the signal frequency, the closer the peak of vibration will be to the entrance to the cochlea, or the oval window. At the peak location, the outer hair cells, through their motility, will amplify the vibration by pumping additional energy into the BM system. The inner hair cells, which are the auditory sensory receptors, are driven by the amplified vibration, and transmit the information to auditory nerves connected to them.
The Outer hair cells serve two main functions. First, they provide amplification to weak sound but not to intense ones. This function is effectively an automatic gain control (AGC) system, compressing a wide dynamic range of input into something that can be managed by the auditory nerve system. Second, they sharpen the contour of the BM frequency response to tones, thus enhancing the frequency selectivity of the auditory system.
Along the basilar membrane, sensory cells at high-frequency locations near the cochlear entrance are more vulnerable to damage than those at deeper, lower-frequency locations. This explains why hearing loss usually begins at high frequencies. At a given BM location, the outer hair cells are more vulnerable than inner hair cells to insults to the cochlea. As a result, even at its early stage, sensorineural hearing loss can be identified with symptoms of losing the outer-hair-cell functions, i.e., a loss of sensitivity to soft sounds, a reduction of dynamic range, and a reduction of frequency selectivity.
When the damage at a region on the BM is so severe that both outer and inner hair cells are destroyed, some researchers call this a "dead" region. Acoustic information normally transmitted via this region must now be transmitted via sensory cells at neighboring regions. Along with the reduction of dynamic range, this loss in the effective number of frequency channels hampers the capacity of the auditory system to transmit information of signals in the auditory world, particularly the speech signals.
Speech signals are particularly affected by the decreased capacity of information transmission with sensorineural hearing loss because speech signals spread over a wide range in both intensity and frequency. Of the two major elements of speech sounds, the vowels are less affected, because they are relatively long and intense, and have energy concentrated at low frequencies. Consonants, on the other hand, are more affected in their perception, because they are short and soft, and typically have energy spread over a wide frequency range. This is unfortunate, because consonant recognition is key to speech understanding.
Speech perception is made even more difficult because of impairment to the frequency resolution, and perhaps also to the temporal resolution. With compromised resolutions, speech segments that can be processed separately in normal ears will now interfere with other segments in time and frequency, making important speech features indistinct or even masked.
The complex mechanisms of sensorineural hearing loss present a challenge for hearing industry. In many ways, a hearing aid does not have the same degree of magic effect that a pair of eyeglasses can produce, because the deficits of cochlear damage usually cannot be fully corrected. With that in mind, there is still much that can be done to improve the listening comfort, the sound quality, and, most of all, speech intelligibility. For so many who suffer the consequences of hearing losses, even a partial recovery of their auditory ability can go a long way in enlightening their life. For this, any effort for making a good hearing aid is a worthy effort.
For more information on hearing , hearing loss, hearing aids or other assistive listening devices, contact:
Manan Hearing Care at 1-800-416-2434 or email email@example.com