Inside the cochlea are very small ‘hair cells’. Each ear has about 24,000 of these specialized cells. They are lined up in two sections. Outer hair cells are lined up in three to four rows, while the inner hair cells are only in one row. The hair cells are tuned like a piano to respond only to a certain frequency. The hair cells use chemicals to send a message to the hearing nerve each time they are activated. The hearing nerve sends the message up to the brain where the signal is decoded and turned into meaningful sounds or speech.
An audiologist is an individual with an advanced degree in hearing and balance science. They have the goal of promoting healthy hearing, and communication that provides a good quality of life for their patients. The audiologist works to prevent hearing loss when possible and identify, assess and provide rehabilitation for hearing and balance problems.
The education of audiologists has changed over the past ten to fifteen years to meet the larger scope of practice. At the Jefferson Balance and Hearing Center, all audiologists have earned a doctoral degree in audiology (Au.D.). The Au.D. degree typically requires four years of intensive study and clinical experience in addition to an undergraduate degree.
The auditory pathway is a series of structures by which sounds are received from the environment and conveyed as signals to the central nervous system. It consists of the outer, middle and inner ear and the tracks along the auditory pathway. For a better understanding of the auditory pathway, consider exploring http://www.neuroreille.com/promenade/english/ear/fear.htm
The cochlea is part of the inner ear, and it is responsible for transmitting sound to the hearing nerve. It is connected to the vestibular system which helps keep us on balance. Scientists are still discovering how the cochlea works at the molecular level, but the following is a basic explanation.
A sensorineural hearing loss is often the result of damage to these small hair cells in the cochlea.
Conductive Hearing Loss
A conductive hearing loss is found when sound does not transfer optimally through the outer and middle ear to the inner ear. There will be a difference in the air conduction and bone conduction responses. There can be many causes of conductive hearing loss including ear wax, an infection of the outer or middle ear, trauma or disease in the middle ear, a hole in the eardrum, or Eustachian tube dysfunction. This type of hearing loss may require medical treatment, but some cases are managed with amplification.
The ear has three parts: the inner, middle and outer ear. If any of these parts is not working correctly there will be symptoms such as itching, discharge, discomfort, fullness, popping sounds, soreness, pain, loss of hearing, tinnitus, dizziness or imbalance. The recommended course of action is to schedule an appointment (call 1-800-JEFF-NOW) to see one of our otologists.
The frequency of a sound is a measured in hertz (Hz) and is defined as how often a cyclical pattern occurs. Low pitch sounds have large, slowly repeating waves, while high pitch sounds have smaller, faster repeating waves.
Hearing is measured by frequency and intensity, or in other words, by pitch and loudness. There are three main types of hearing loss: conductive, sensorineural and mixed. The type of hearing loss is further described by a degree of hearing loss.
Mild hearing loss: 25-40 dB HL
Moderate hearing loss: 41-55 dB HL
Moderately severe hearing loss: 56-70 dB HL
Severe hearing loss: 71-90 dB HL
Profound hearing loss: 90+ dB HL
A typical hearing test begins with the audiologist looking into the ear canal with a small light or otoscope. This is done to examine the ear canal and look at the ear drum.
Next, the audiologist will place a small, soft probe into the ear canal to evaluate the middle ear system. You may hear a buzzing and feel a small change in pressure during this portion of the exam.
The third portion of the exam will examine the inner portion of the ear, the cochlea. Once again, the audiologist will place a small probe into your ear canal and you will need to sit quietly and listen to the tones presented. Next, the audiologist will put ear phones on you and, using an audiometer that is calibrated to measure hearing precisely, you will be asked to respond to tones that are presented through the ear phones. The audiologist will record your responses across all frequencies tested.
Finally, the audiologist will measure your ability to understand speech that is presented at a comfortable listening level. At the end of the evaluation, the audiologist or your physician will review the results of the hearing test with you.
When everyday sounds become painful or intolerable a person may be suffering from hyperacusis. The worst thing someone can do who has a decreased tolerance to sound is wear earplugs. One study looked at individuals with normal hearing to see the affects of auditory deprivation and wore ear plugs for a period of time. They reported a decreased tolerance to sound once the earplugs were removed. The good news is that they were able to quickly return to normal once their brains had a chance to get used to everyday sounds again. It may not seem to follow logic, but avoiding sound at levels that are not dangerous is the worst thing someone with hyperacusis can do. Rather, they need to build up their tolerance to sound either in a self-guided program, or through a more structured therapy.
Intensity is the amplitude of a sound wave. Sound intensity, which is expressed in decibels (dB), is measured in relation to an accepted reference, such as the threshold at which an average person can hear a sound. The greater the intensity, the louder the sound and the greater the decibel level measurement. Below is a table of environmental sounds and their decibel level. There are many ways to measure a decibel, but one common method is to calculate the sound pressure level at the ear drum or dB SPL. As sound gets louder, small changes in dB SPL can make a large difference in comfort.
|Normal breathing||0 dB SPL||Just audible|
|A room in a quiet house at midnight||30 dB SPL|
|Easily audible whisper||40 dB SPL|
|Window air conditioner||55 dB SPL|
|Typical conversation||60 dB SPL|
|Busy restaurant||65 dB SPL|
|Loud speech||70 dB SPL|
|Inside an automobile traveling at highway speeds||80 dB SPL|
|Food Blender||90 dB SPL||Ear damage possible if sustained for 8 hours|
|NYC subway station||100 dB SPL||Ear damage possible if sustained for 2 hours|
|Symphony concert, at peak levels||110 dB SPL||Ear damage possible if sustained for 30 minutes|
|A loud rock band||120 dB SPL||Ear damage possible is sustained for 7 minutes and 30 seconds|
|Gunshot||140 dB SPL||Ear damage possible is sustained for 30 seconds|
|Fireworks at 3 feet away||190 dB SPL||Ear damage possible with exposure of less than 2 seconds|
|Rocket engine, nearby||0 dB SPL||Instantaneous ear damage|
A disorder of the inner ear that can affect hearing and balance. It is characterized by episodes of dizziness and tinnitus and progressive hearing loss, usually in one ear.
Mixed Hearing Loss
A mixed hearing loss is a combination of a conductive and sensorineural hearing loss. There is both a problem with the transmission of sound energy through the auditory system, as well as a problem with the cochlea or hearing nerve. This type of hearing loss may require both medical intervention and amplification.
Neuromonics is a tinnitus treatment that provides a decrease in awareness and disturbance of tinnitus.
A newer, commercial form of tinnitus therapy, termed Neuromonics™, is a combination of acoustic therapy with a six-month course of education and support. A low-level broadband noise is presented for several hours per day. The patient receives pre-conditioning counseling to achieve relaxation and lessening of the tinnitus symptoms. Active treatment involves desensitizing the brain to reprogram and filter out the tinnitus. Based on a neurophysiologic model, the combination of masking with the low-level broadband noise and counseling achieve habituation of the reaction to tinnitus and perception of the tinnitus itself. This is not a cure, but studies have shown that Neuromonics helps patients achieve relief in a shorter amount of time than other traditional tinnitus treatments.
This model for tinnitus was first described by Pawel Jastreboff, PhD, ScD in the 1990's. He described that many areas of the brain are playing a role in tinnitus and hyperacusis rather than just the auditory system. The limbic system, part of the brain that assigns emotion to an event or object, has been found to play a major role. The brain’s perception of the sound and its reaction to the sound are two distinct ideas. We have not yet found a cure for tinnitus, although there are treatments to help reduce the impact of our brain’s reaction to the tinnitus or hyperacusis.
The otolaryngologist or ENT (ear, nose and throat) is a surgeon who, following medical school, has completed a residency providing additional medical and surgical training for a very complex specialty. There are some ENTs who have completed additional study and surgical training (a fellowship) to become neurotologists, whose specialty is the ear.
Sensorineural Hearing Loss
A sensorineural hearing loss is found when sound does not transmit to the brain in a normal manner. This may be due to a problem with the sensing organ, cochlea or along the auditory nerve, CN VIII. A typical hearing test cannot distinguish between a problem with the sensing portion of the ear versus the nerve, thus it is described as a sensorineural hearing loss. Often there is no surgical or medical intervention for a sensorineural hearing loss, and the best course of treatment is amplification. For individuals with a profound hearing loss, a cochlear implant is an option.
This is the presence of sound such as ringing, buzzing, whistling, clicking or humming originating from the ear or head. The pitch (frequency) and loudness (intensity) of the tinnitus is variable between and within patients. Tinnitus can be subjective or objective. Subjective tinnitus is the most common, and only the person with tinnitus can hear the sound. Objective tinnitus is rarer, but another person can hear the sound coming from the ear often with the use of a stethoscope.