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How We Hear

Anatomy of Our Ear

To understand hearing loss, the best place to start is inside the ear. It is the place where many complex and delicate functions combine to create what we call hearing. Your ear is an amazing organ that can perceive sounds from barely audible to very loud at frequencies or pitches of 20 to 20,000 Hz. It can pinpoint the direction of a sound source to an amazing degree of accuracy.

The human ear consists of three parts: the outer ear, the middle ear, and the inner ear.

Anatomy of the Ear


The outer ear includes the visible part of the ear (pinna) and the ear canal. Sound is collected and directed through the ear canal.

The middle ear is an air-filled space separated from the outer ear by the eardrum. The middle ear contains three small bones (ossicles), which make up the ossicular chain. These bones connect the eardrum to the inner ear.

The portion of the inner ear responsible for hearing is called the cochlea. It is full of fluid and has thousands of tiny nerve fibers.


Additional terms

External auditory canal - part of the outer ear, a one-inch long, one-quarter inch diameter tube that ends at the eardrum. Its shape helps to boost speech frequencies.

Eardrum or tympanic membrane - a membrane about 1/3 of an inch in diameter that stretches across the inner end of the external ear canal. It vibrates in response to sound waves and forms the boundary between the outer ear and middle ear.

Cochlea - converts sound waves to nerve impulses through movement of thousands of tiny hair cells.

Acoustic hair cells - located inside the cochlea, these convert mechanical sound waves into electrical signals.

Auditory nerve - transmits the electrical signals from the acoustic hair cells from the inner ear to the brain.

Brain - processes the electrical signals from the auditory nerve that we interpret to be "sound."

How We Hear

The process we know as hearing begins when your funnel-shaped outer ear or pinna collects sound waves, then channels them through to the end of the ear canal, where the eardrum is located. The impact vibrates the eardrum and touches off a process in the auditory-vibrations pass from the hammer (malleus), to the anvil (incus), then to the stirrup (stapes). The stapes footplate fits into the oval window, which forms the entrance to the inner ear, where the cochlea is located.

The movements continue to the cochlea, one of the two main structures of your inner ear. It is filled with fluid and contains thousands of microscopic acoustic hair cells. (The other main structure of the inner ear, the semicircular canals, governs balance.) The fluid's wave-like action causes the acoustic hair cells to bend. This converts the mechanical sound signal into electric stimuli, which are transmitted via the auditory nerve to the brain.

The auditory nerve carries these impulses to the cochlear nucleus and then to the hearing center of the brain. Nerve pathways here divide and lead to a pair of auditory corti, one located in each half of the brain. There the central auditory system processes the auditory information.

The result of this complex process is what we perceive as "sound."

Speech and Balance Are Intimately Connected to Hearing

Speech and Hearing

 Hearing and speech affect our ability to communicate and experience the world around us. An enormous degree of what babies learn comes to them through their ears. They stop crying or coo when they hear their mothers talk to them. They may react (smile) to a change in a tone of voice. Parents who suspect hearing difficulties in their babies may notice that their child is not reacting to a new sound, responding to "no" or enjoying rattles and other toys that make sounds. Experts say parents who discuss their baby's suspected hearing problem with their doctors early may be able to reduce the impact it may have on speech development. Hearing problems may make older children, adults and the elderly more silent and socially withdrawn.

Balance and Hearing

The vestibular system in the inner ear controls our sense of balance and relies on information from a number of sources, including hearing, to operate. Because of this intimate connection between balance and hearing, impairments of the inner ear such as Meniere's Disease involve symptoms that may include both dizziness and progressive deafness. Age-related hearing loss affects 30-35 percent of the U.S. population between the ages of 65 and 75, and 40 percent of those over 75 years of age. Likewise, one study of 65- to 75-year-olds found that one-third also experienced dizziness and imbalance. Balance-related falls account for more than half of accidental deaths in the elderly.

Your vestibular system consists of three semicircular canals, each governing a different movement: up/down, side to side, and tilting. These canals contain sensory hair cells that respond to movement of hte inner ear fluid. When your head moves, these hair cells send nerve impulses to your brain via a portion of the acoustic nerve. The brain stem and the cerebellum process the vestibular impulses.

Causes of Hearing Loss

Hearing Loss - A Gradual Awareness

Millions of Americans of all ages suffer from hearing loss. It is a physical, not a mental health problem that can develop at any time. Most often, it is gradual and painless. People may not realize for several years that this problem is affecting them because it develops so slowly that at first it may be barely noticeable. It can inhibit people's ability to experience the sounds and voices around them. And this affects their own lives and the lives of those around them.

There are many causes of hearing loss, including:

  • Aging
  • Long-term exposure to noise
  • Heredity
  • Illness
  • Reactions to medications
  • Injury
  • Ear Wax

Ear Wax

The outer foundation of the ear canal is cartilage covered with skin that contains hair and glands that secrete cerumen or earwax (a yellow or brown substance). Together the hair and earwax help prevent "invaders" such as insects, dust and bacteria from getting into the ear. Typically, the earwax traps the dirt, dries and flakes it out of the ear. The ear canal can become blocked by attempts to clean the ear and push wax deeper into the ear. Blockage can cause temporary hearing loss. And probing to "clean" the ear canal with cotton swabs can damage the fragile structures in your ear.

Ear canals should take care of themselves. Cleaning by wiping the external portion of the ear with a soft cloth or tissue over the finger should be enough. If you experience a hearing loss, tinnitus (ringing in the ear), earache or a sensation of fullness in the ear, then you may have an earwax blockage. Your physician can prescribe or recommend softeners or clean the wax out in the office.

Types of Hearing Loss

There are three different types of hearing loss.

Conductive hearing loss is caused by injury to, or problems with, the bones, eardrum and membranes, which carry sound from the external ear through the middle ear to the inner ear. This type of hearing loss can sometimes be medically or surgically corrected.

Examples of conditions that may cause a conductive hearing loss include:

  • Conditions associated with middle ear pathology such as fluid in the middle ear from colds, allergies (serous otitis media), poor eustachian tube function, ear infection (otitis media), perforated eardrum, benign tumors
  • Impacted earwax (cerumen)
  • Infection in the ear canal (external otitis)
  • Presence of a foreign body
  • Absence or malformation of the outer ear, ear canal, or middle ear

Sensorineural hearing loss (also known as nerve deafness) occurs when the bones, eardrum and membranes are intact but the inner ear (cochlea) deteriorates as the result of causes that can include the aging process or degeneration of nerves (retrocochlear) leading from the inner ear to the brain.

Examples of conditions that may cause a sensorineural hearing loss include:

  • Diseases
  • Birth injury
  • Drugs that are toxic to the auditory system
  • Genetic syndromes
  • Noise exposure
  • Viruses
  • Head Trauma
  • Tumors

Mixed hearing loss is when there are elements from both conductive and sensorineural hearing loss. This occurs when there is damage or disturbance to the outer or middle ear and damage to the inner ear.

Symptoms of Hearing Loss

Because hearing loss is gradual, you may not be aware of the extent of its loss until someone else brings it to your attention. It may be difficult to accept this news, but it is important to realize that recognizing a hearing loss is the first step toward improving the quality of your life.

Often, higher pitched sounds, such as women and children's voices or birds singing are the first sounds that begin to "disappear." Then the person may notice symptoms including:

  • Difficulty hearing in public gatherings such as concert halls, theaters, or houses of worship where sound sources are far away
  • Difficulty hearing television and/or the telephone
  • Difficulty understanding conversation in group settings
  • Misinterpreting what others say
  • Hearing noise ok, but not being able to understand others' speech; people seem to be "mumbling" when they are speaking.

Hearing difficulties can be a source of embarrassment. Adults who experience them usually develop a variety of ways of coping in difficult listening situations, such as:

  • Constantly asking others to repeat themselves or speak louder
  • Turning the head to one side while listening to sounds or speaker
  • Turning up the TV, radio or stereo volume to a level that disturbs others
  • Avoiding social gatherings such as at restaurants or parties where background noise makes it difficult to understand conversation

Testing For Hearing Loss

In testing for hearing loss, a Hearing Care Professional will administer a painless, quick and safe test that checks your ability to recognize tones and everyday words at different volume levels. The data produces a unique hearing pattern that is recorded on a chart called an audiogram. The Hearing Health Care Professional uses the data from your audiogram to determine whether you might benefit from hearing aids or whether medical treatment is indicated.

Hearing loss is especially prevalent in older people. If you are over age 50, consider a yearly hearing test as an important part of your physical checkup.


The following questions will help you determine if you, or a loved one, should have a hearing test performed by a Hearing Health Care Professional. There are two questionnaires to choose from. One is for you to answer about your own hearing. The other is about the hearing of a loved one. Just answer YES or NO to each question, then review the information that follows when finished. Remember, detection of a hearing problem is the first step to improving your hearing health.

Questionnaire: Do I have a hearing loss?

  • Do people always comment that the volume on your TV or radio is too loud?
  • Have you missed visits and calls from people because you didn't hear the doorbell or telephone ringing?
  • Do you have trouble following conversation in crowded or noisy settings?
  • Do people seem to mumble and not speak clearly during conversation?
  • Do people tell you that you speak too loudly in conversation?
  • Do you frequently ask people to repeat themselves?
  • Do your friends and family suggest that you have a hearing problem?
  • Do you have a difficult time understanding the words of popular songs when listening to the radio?

    Questionnaire: Does someone I know have a hearing loss?

    • When you come to visit does the person you know hear your knock on the door or the doorbell?
    • Does the person you know complain about having a difficult time hearing on the telephone?
    • Does the person you know always ask you and others to repeat yourselves?
    • In crowded settings, does the person you know complain about not understanding what people are saying?
    • Does the person you know always turn the volume on the TV or radio up to an uncomfortable level just to hear a program or music?
    • Does the person you know often complain of ringing in the ears?

      If you answered "YES" to any of these questions, you or your loved one may want to have a hearing test to determine if there's some degree of hearing loss.

      If you suspect a hearing loss, you can consult the following Hearing Health Care Professionals:

      • Audiologists
      • Hearing aid practitioners
      • Otolaryngologists
      • Otologists


      The Sound That Won't Go Away

      Hearing loss may be too much "silence" for some, but tinnitus is a sound that won't go away. Tinnitus, or ear ringing, may be experienced as a buzz, whistle, roar or chirping. It is the perception of sound without an external cause. Many people are not particularly bothered by it, but as many as five million Americans find tinnitus chronic, irritating, and even unbearable.

      Causes of Tinnitus

      There are at least 400 known causes for tinnitus including noise trauma, orthodontia disorders and certain medications, but it may be hard to pinpoint which one of these is the basis for a particular case of tinnitus. Half of all tinnitus is accompanied by hearing loss. Unfortunately, there is no completely proven medical cure.

      Help For Tinnitus

      There is hope for many thanks to tinnitus control devices and tinnitus control hearing aids. These have been developed to shift awareness away from the relentless tinnitus noise and thereby relieve the stress of tinnitus. They emit a pleasant sound that is therapeutic, like the sound of gently rolling waves. Tinnitus control hearing aids are combination devices that produce the therapeutic sound and assist hearing loss the same way regular hearing aids do. Both types of devices are designed to be used in combination with tinnitus therapy and /or counseling for optimum results.

      How Hearing Aids Help

      No two people have exactly the same hearing loss. But pioneering research and development in the hearing aid industry, with Siemens in the forefront, has led to the design of a very wide selection of technologically advanced hearing aids and other hearing support systems to help people meet the challenge. Approximately 10 percent of hearing losses may be helped medically. And the remaining 90 percent may benefit from hearing aids. Solutions well-matched to individual needs are now possible.

      Hearing aids can help you re-establish connections to the world. They are made to selectively increase the volume of the sounds you want to hear. They can make soft sounds audible, while at the same time making moderate or loud sounds comfortable. Hearing aids are designed to provide relief in both noisy and quiet situations. Wearing hearing aids can put you at ease during conversations and make you less likely to have to ask others to repeat themselves.

      No hearing aid can solve every hearing problem or restore normal hearing, but they are designed to provide amplification so that you can hear and understand better.

      Binaural Amplification

      Two Ears Are Better Than One

      We have two ears for a reason. Hearing with both ears is what nature intended; it allows the brain to process sounds naturally so we hear sounds accurately and get a sense of balance and direction. Hearing loss causes the brain to misinterpret sounds. When a hearing loss affects both ears and only one ear is amplified, the brain is only receiving half of the accurate information. Binaural amplification (wearing two hearing instruments) can help us hear as nature intended.

      • Approximately 80 percent of those with hearing loss have hearing loss in BOTH ears
      • Amplifying only one ear makes it more difficult to hear in noise, understand speech and detect where sounds are coming from
      • The ear not amplified can become fatigued and strain to hear
      • Studies show that even when a hearing loss is worse in one ear, wearing two hearing instruments produces the most benefit

      Years of clinical research have shown the benefits of binaural amplification.

      • Increased Speech Understanding
        • Binaural amplification delivers more of the sounds you need, so your brain can process the sounds correctly, making it easier and more comfortable to understand speech in noise
      • Enhanced Sound Quality
        • When wearing two hearing instruments, volume levels can be set lower, minimizing the risk of distortion and auditory fatigue therefore making sounds and the act of listening more comfortable and natural
      • Improved Localization
        • When the brain receives sound from both the right and left ears it makes it easier to locate the direction of sounds (called localization), important in daily situations including being able to tell from which direction traffic is coming

      Binaural amplification is more beneficial than ever with the latest hearing instrument technology.

      • e2e wireless
        • Exclusively in Siemens hearing systems, this revolutionary technology enables two hearing instruments to exchange information and operate in complete synchronization
      • Directional microphone systems
        • These highly developed and intelligent systems are designed to detect the source of background noise and then reduce sounds from that direction, to improve speech intelligibility (even if the sound is moving, like a truck riding down the street or if there are multiple noises)
      • Automatic volume control
        • Automatically amplifying quiet sounds and helping limit loud sounds makes hearing instruments more comfortable and convenient
      • Voice activated noise reduction
        • This digital sound processing system continuously monitors for speech sounds, automatically reducing the level of some background sounds when detected

      Hearing Aid Technology

      Todays hearing instruments contain sophisticated digital circuitry available in all models from Behind-the-Ear to In-the-Ear and even In-the-Canal models that allow more functions and features than ever before.

      Digital Sound Processing

      • Automatic sound processing
        • Incoming sound is continually analyzed and processed to best amplify speech while reducing unwanted noise
        • Soft sounds are given more amplification, while very loud sounds are given little or no amplification
        • Often creates hands-free operation with no need for external controls such as volume control wheels
        • Makes hearing instruments simple to use and comfortable for the wearer
      • Directional microphone systems
        • Proven to improve speech understanding in noisy environments
        • Helps you focus on sound coming from in front of you, by reducing sound coming from the side and behind you
        • The latest directional microphone systems automatically adapt and reduce multiple noise sources around you
        • New directional technology includes systems that use three microphones
      • Speech & Noise management technology
        • Helps minimize or reduce background noise in many situations
        • Allows for special listening programs to be set that offer personalized sound processing for specific listening needs such as listening to music
      • Feedback Cancellation
        • Continually analyzes incoming signals and adjusts seamlessly and instantaneously to minimize feedback (whistling)
        • Maintains excellent sound quality
        • Advanced systems avoid unnecessary cancellation of high-pitched external signals like music or the beeps from a microwave oven
      • Multiple Listening programs
        • Adjusts the way sound is processed to adapt to specific listening situations including listening on the telephone or to music
      • Wireless technology
        • Highly advanced instruments use wireless technology to literally communicate with each other when wearing two hearing instruments (binaural amplification)
        • Sound processing is synchronized for optimized sound quality
        • Wearers can use one control to operate both instruments
      • Intelligent features and accessories
        • Remote control
          • Allows volume and listening mode changes to be done discreetly, without having to touch the hearing instrument
          • Enables volume change and multiple listening programs on instruments too small for push buttons or volume control wheels such as with Completely-in-the-Canal models
          • Advanced remote controls can display hearing instrument settings including battery status, listening mode and volume
        • Telecoil
          • Special feature that amplifies only telephone signals and not other sounds
          • Operated automatically when telephone is placed near hearing instrument or manually by a push button or switch
        • Audio input
          • Allows attachment, either with or without a wire, to FM systems (assistive listening devices used by children with hearing loss in schools), televisions, tape recorders and other devices.