The ear is a complex and delicate organ that allows you to detect passing waves of sound energy and thus, hear the sounds of the world around you.  The ear also contains an organ that helps you keep your balance.  Most of the ear is hidden inside the head so you are seldom aware of the job that it is doing until the system starts to fail somewhere.  Fortunately, most hearing loss can be helped through medical care, surgery, or most often through the wearing of hearing aids. 

 

When something makes a noise, it sends vibrations, or sound waves, through the air.

The human eardrum is a stretched membrane, like the skin of a drum. When the sound waves hit your eardrum, it vibrates and the brain interprets these vibrations as sound.

Actually, as most things having to do with the human body, it is a little more complicated than that.

After the vibrations hit your eardrum, a chain reaction is set off. Your eardrum, which is smaller and thinner than the nail on your pinky finger, sends the vibrations to the three smallest bones in your body. First the hammer, then the anvil, and finally, the stirrup. The stirrup passes those vibrations along a coiled tub in the inner ear called the cochlea.

Inside the cochlea there are thousands of hair-like nerve endings, cilia. When the Cochlea vibrates, the cilia move. Your brain is sent these messages (translated from vibrations by the cilia) through the auditory nerve.

Your brain then translates all that and tells you what you are hearing. Neurologists don't yet fully understand how we process raw sound data once it enters the cerebral cortex in the brain.

Did you know?

Your ears aren't just good for helping you hear. They help you keep your balance as well. Near the top of the cochlea are three loops called the semi-circular canals. These canals are full of fluid that moves when you move your head. It pushes up against the cilia and sends messages to your brain that tells it how your body is moving.

You know that feeling of dizziness after you have been spinning around? Well, the fluid in you ears spun as well. That makes the cilia move in all different directions and confused your brain.

Children have more sensitive ears than adults. They can hear a larger variety of sounds.
Dolphins have the best sense of hearing amongst all the animals. They are able to hear 14 times better than humans.
Too much fluid putting pressure on your eardrums causes earaches. They are often a result of infection, allergies, or a virus.

What HearSource Hearing Aid Do To Correct Hearing Loss 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. Fig 2 Fig 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. 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 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 io 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: HearSource at 1-800-416-2434 or email: info@hearsource.com