About Hearing

The ear is a sophisticated organ that transmits the sounds we hear into electrical impulses that are interpreted by the brain. The process of hearing and interpreting sound is accomplished at a fantastic speed. To achieve this remarkable feat, each part of the ear - outer, middle and inner ear - fulfills a specific function. Outer ear The outer ear is composed of the pinna, the familiar visible portion of the ear, and the ear canal. The shape of the outer ear serves to give preference to sounds originating from the front. The shape of the ear canal serves to enhance frequencies that are important for hearing speech. Middle ear The middle ear consists of the eardrum, or tympanic membrane, and three tiny ear bones, or ossicles. The ossicles are the smallest bones in the human body. Although named the malleus, incus and stapes, they are often referred to as the hammer, anvil and stirrup because of their characteristic shape. Besides their role in the transmission of sound, these bones help to protect the ear from damage by constricting and limiting sound transmission when sound is too loud. The middle ear also contains the Eustachian tube, which connects with the throat, and serves to ventilate and regulate pressure in the middle ear. Inner ear The inner ear is composed of the semi-circular canals, which are important for balance, and the fluid-filled, snail-shaped hearing organ, the cochlea. How we Hear/Transmission of Sound The funnel shaped outer ear functions to collect sound waves which are then transferred through the ear canal to the eardrum. Sound waves cause the eardrum to vibrate. This vibration stimulates the movement of the middle ear bones, which are attached to the eardrum on the middle ear side. These bones amplify the vibrations received by the eardrum and transmit them to the oval window, a small membrane on the cochlea, which separates the middle ear from the inner ear. On the cochlear side of the oval window is fluid (or lymph) which fills the cochlea. Vibration of the oval window causes pressure waves within the cochlear fluid. The pressure waves stimulate movement of thousands of acoustic hair cells in the cochlea, converting the sound signal into electrical stimuli via neurons. These electric stimuli are transmitted to the brain via the eighth cranial nerve, or auditory nerve. In the brain these stimuli are processed and are perceived as sound.

About Hearing Loss

Approximately 28 million Americans are estimated to have some type of hearing impairment. Hearing loss affects people of all ages and from all walks of life. Among older people, it is the most common health problem, second only to arthritis. There are many causes of hearing loss. In many cases, hearing loss happens gradually and generally worsens with age. Hearing loss caused by aging is known as presbycusis. Disease, infection, heredity, head trauma, exposure to loud noise and certain medications may also cause hearing loss. In some cases, the cause of hearing loss is unknown. Types of hearing loss Sensorineural hearing loss: Sensorineural hearing loss is caused by inner ear damage. Sometimes referred to as "nerve losses", these comprise 95% of all hearing losses. Some causes include presbycusis/aging, noise exposure, heredity, viral infection to the brain such as meningitis, and in rare cases, ototoxic medications. Although there is no cure for sensorineural hearing loss, advances in hearing aid technology can help the vast majority of people with this type of hearing problem. Conductive hearing loss: When sound transmission through the outer or middle ears is prevented or impaired, this is known as a conductive hearing loss. Some causes of conductive hearing losses are obstruction of the ear canal by impacted earwax, head trauma affecting the middle ear bones, perforation of the eardrum, fluid build up in the middle ear, and otosclerosis (a stiffening of the middle ear bones). About 5% of hearing losses are conductive in nature, and many can be treated medically. Mixed hearing loss: A mixed hearing loss is one that has both sensorineural and conductive components. A word about tinnitus: The word tinnitus comes from the Latin word for ringing. Tinnitus is a sound in the ear such as a ringing, buzzing, whistling or chirping - without the presence of an external sound. Approximately 10 million people in the United States are estimated to have tinnitus, and one in four people will experience it at least once in their lifetime. Tinnitus may be caused by exposure to a loud noise, and often will subside soon after the incident. The cause of tinnitus may be as simple as a build-up of earwax. Tinnitus may also be caused by an underlying medical condition such as a tumor growing on or near the auditory nerve. In some cases, treating the underlying condition will resolve the tinnitus. If tinnitus remains after treatment or is not caused by an underlying medical condition, there are non-medical solutions available for chronic tinnitus sufferers. In approximately half of all cases, tinnitus is accompanied by hearing loss. With the onset of acute tinnitus (less than 3 months), especially when accompanied by hearing loss, a doctor should be consulted. In cases where hearing loss is also present, tinnitus often improves when a hearing instrument is properly fitted.

Protecting Your Hearing

Exposure to excessive noise during work or leisure activities can increase a person's risk of hearing loss and contribute to worsening an already existing hearing problem. A continuous exposure of 85 decibels (dB) will begin to have a detrimental effect on our hearing. An example of this would be the noise of a street with constant heavy traffic. If the exposure to loud noise lasts for a long time, the cells responsible for our sense of hearing will be irreversibly damaged. Doctors consider exposure to loud music, such as a rock concert or via headphones, to be particularly dangerous since the sound intensity can sometimes reach 110 - 120 dB. The traumatic effect of a sudden loud sound such as an explosion can also permanently damage hearing. Other activities that may cause hearing loss over time include: use of a personal radio/CD player/stereo at a high volume; use of firearms; operating heavy machinery; use of power tools. The good news is that the noise in these cases is usually easily managed by turning down the volume or by wearing ear protection. Federal regulations govern allowable noise levels in the workplace, as well as the employer's role in providing ear protection. In addition to using ear protection, those who are regularly exposed to noise should have their hearing tested regularly. Certain medications are toxic to the ear. If you have a hearing loss, be sure to inform your doctor of your condition before beginning any new medications. There may be instances where other medications which are not toxic to the ear can be substituted. How loud is too loud A general rule of thumb is if you have to raise your voice to be heard over the music/noise, it is too loud. According to the National Institute on Deafness and Communicable Diseases, noises above 85 decibels can cause hearing damage. Ear Protection Since there is no cure for noise-induced hearing loss, prevention is the sensible alternative. Modern devices which protect your hearing, from commercially available earplugs to custom-made earmolds with various filter systems, can give effective protection against noise. If you are exposed to continuous noise in your leisure activities or at work, contact us for advice on the latest methods of hearing protection which would provide the most benefit and best suit your hearing needs.