Introduction to hearing loss
 - How the Ear Works
 - The Hearing test
 - The Audiogram
 - The Sounds of Speech
Types of Hearing Loss
Frequently Asked Questions

Babies learn language early by experiencing the world around them with all of their senses. Following hearing screening, the next step involves testing and diagnosis. When a child is diagnosed with a hearing loss there is much to do and learn. This section includes:

• How the ear works
• Descriptions of common hearing tests
• An explanation of the audiogram
• Types of hearing loss

A good starting point is to learn how the ear is designed to work.

Sound is made up of tiny vibrations that move through the air. The process of hearing includes both the ear and the brain, with the ear changing the sound vibrations into a signal that can be understood by the brain. The brain is the most important part of hearing since that is where sounds are converted into meaningful information.

The main purpose of a hearing test is to determine the degree, shape, and type of hearing loss. Characteristics of your child's hearing loss can be determined using a number of different tests. The type of measure used depends on the child's age and abilities. Test results are then used to develop a plan to maximize your child's communication skills. Most babies with hearing loss benefit from hearing aids and other amplification devices. They may also benefit from therapy and educational programs.

How the Ear Works
The ear changes sound vibrations into a signal that can be understood by the brain. The ear has three major regions, these are the middle, inner and outer ear. Each part of the ear has a different job.

• Outer Ear:
  

  The outer portion of the ear is cupped so it can capture sound vibrations that move through the air.

  The vibrations travel through the outer ear canal and collide with the eardrum. This causes the eardrum to vibrate.

• Middle Ear:
  

  The vibration of the eardrum moves the three small bones called ossicles in the middle ear. The common names of the bones are the hammer, anvil and stirrup. They are also known as the malleus, incus and stapes. These bones amplify the vibration and transfer the sound waves to the cochlea in the inner ear.

• Inner Ear:
  

  The cochlea is a small snail-shaped channel through the temporal bone. There are three cochlear channels filled with fluid within the cochlea. The vibrations from the ossicles are absorbed into the fluid channels like waves in a pond.

  The middle channel contains the organ of Corti and sensory hair cells called cilia. Movement of the fluid starts a chain reaction that causes the cilia to bend.

  It is this bending of hair cells that translates movement into electrical impulses that move through the auditory nerve to the brain.

• Brain:
  

  The auditory cortex in the brain interprets the neural impulses into a meaningful message. We interpret the message according to our experiences in life. This process of converting air waves into meaningful sounds occurs in only a fraction of a second.

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The Hearing Test
Hearing tests are used to measure the softest sounds your child can hear. Different techniques are used depending upon the age of the child. Your child will regularly have hearing tests. The results of the hearing test are used to describe the type, degree and shape of hearing loss. The techniques and types of hearing tests used to test your child's hearing will change as your child gets older.

Auditory Evoked Potentials (AEP)
This test is used with babies younger than six months old and for some young children. While the child is sleeping, sounds are presented through earphones. Sensors placed on the forehead and behind the ears measure the way the child's brain responds to different sounds. When the sound can be heard, the sensors detect brain responses. It is important that the child is very quite during the test, so sometimes the child is given some medicine to help them sleep. The test is about two hours long. Auditory Evoked Potentials (AEP), Auditory Brainstem Response (ABR), and Brainstem Auditory Evoked Response (BAER) are all common names for this test.

Visual Reinforced Audiometry (VRA)
This technique is used for children 6 months to about 3 years old. First the child is taught to make a specific response, such as a head turn, when they hear a sound. The child is reinforced visually by an animated toy or bright lights. Sounds are presented through earphones during testing. Since the reinforcement is visual this technique is called visual reinforced audiometry. It may take more than one appointment to get all of the testing done.

Conditioned Play Audiometry (CPA)
This game-like test is used for children 3 to 6 years old. The game involves putting a block in a bucket or putting a peg on a board when they hear a sound. The child is taught to make the response only when they hear the sound. Sounds are presented through earphones. Testing can usually be completed during one or two appointments. After a child is about six years old, they can be tested like an adult.

Speech Recognition Threshold (SRT) or Speech Awareness Threshold (SAT)
This test measures the loudness necessary for speech to heard at the quietest level possible. The child is asked to repeat a two-syllable word such as 'baseball.' These results help confirm results of the pure tone audiogram. Special speech tests have been designed for use with children and non-English speaking populations. Children may be asked to point to body parts, toys, or pictures, if they cannot repeat words. The SRT and word recognition tests (described below) may be given to compare the child's performance with or without a hearing aid or assistive listening device.

Word Recognition (Speech Discrimination)
This test measures how clearly the child hears speech and may be an indicator of how well the child will learn language. Words are presented at a comfortable hearing level for the child. The audiologist asks the child to repeat a list of two-syllable words and records the percentage of correct responses. If a child is unable to speak, he or she can point to pictures instead. The audiologist may also present this test against a noisy background to predict the child's hearing performance in a noisy environment.

Lip Reading/Speech Reading
The audiologist or teacher of the deaf or hard or hearing may give this test to a child beginning at age 5. The child must look and listen to the speaker, who says different words or sentences, and must repeat the word/sentence back in response. There are several tests available depending on the child's age. A child's performance is measured as a percentage of correct responses with or without a hearing aid. These tests are different than those listed earlier because they allow a child to use both vision and hearing.

The Audiogram
The audiogram is a tool the audiologist uses to chart your baby's hearing. The softest sounds that your child can hear are charted on the audiogram. Sounds can be soft or loud and low pitched or high pitched. Both the loudness and the pitch of a sound are shown on the chart. The audiologist uses the information from this form to build a program that maximizes your child's abilities.

Loud and Soft Sounds

The loudness is measured in decibels (dB) and is represented by horizontal lines on an audiogram chart. Marks on the audiogram represent the softest sound you can hear at each frequency. Very soft sounds are located at the top of the chart Very loud sounds are located at the bottom of the chart   The softest sounds that you can hear at each frequency or pitch is known as the threshold. The thresholds for each ear are often different. Decibels are also referred to as hearing level or intensity.

Pitch or Frequency of Sounds

Pitch or frequency is measured in Hertz (Hz). Low pitched sounds, like a big drum, are located on the left side of the chart High pitched sounds, like a bird chirp, are located on the right side of the chart A loud low pitched sound, like a fog horn, will be marked in the lower left corner of the chart and a soft high pitched sound, like a mouse squeak, will be marked in the upper right corner of the chart.

Your child's team will frequently refer to your child's thresholds. The patterns formed by these thresholds are described as the degree and the shape of your child's hearing loss.

The Sounds of Speech
Most children learn to talk by listening to others. They learn to imitate sounds and the way we use words. The pitch (hertz Hz) and loudness (decibels dB) of all speech sounds are important.

The sounds your child will have trouble hearing and learning can be predicted by looking at their audiogram. Most of the speech sounds occur in the middle pitch range from 500 to 4000 Hz. This area of the audiogram is often shaded in yellow. The audiogram shows all the sounds of speech according to their pitch and loudness. For example, the "s’ sound in the word "cats" is high in pitch and fairly soft. In contrast, the "o" in "bow" is low in pitch and fairly loud. The goal of amplification is to make all of these speech sounds loud enough for your child to hear.

People can hear many sounds. The softest sounds you can hear fall into ranges on the audiogram. If you can hear sounds as soft as 0 and 15 decibels (dB) then you hearing is considered normal.

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The Degree of Hearing Loss
The levels of the patterns on the audiogram indicate the degree of hearing loss. The degree of hearing loss refers to the average amount of hearing loss for speech sounds.

The degree of hearing loss is measured in decibels (dB). For children, a mild hearing loss ranges from 20 dB to 40 dB, moderate from 41 to 60 dB, severe from 61 to 90 dB, and a profound hearing loss > 90 dB HL. The degree of hearing loss can be the same or different in each ear.

A child with a mild high frequency hearing loss will have trouble hearing and understanding soft speech, speech from a distance and speech with background noise. With moderate hearing loss the child will have difficulty with conversations even at close distances.

You will hear both the terms: deaf and hard of hearing. Deaf is a term used to describe persons who have a hearing loss greater than 90 decibels. It may also be used to refer to those who consider themselves part of the deaf community or culture and choose to communicate using American Sign Language. Hard of hearing is a term used to describe those who have a mild to severe hearing loss.

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The Shape of Hearing Loss
The slope or curve of the lines on the audiogram indicates the shape of hearing loss. The shape of the hearing loss could be flat, or about the same for all pitches. The hearing loss could be slightly worse in the high frequencies, or gradually sloping. It is very common for a hearing loss to be a little worse for the high pitches than the low pitches. Another common pattern is a "cookie-bite". In this pattern the hearing loss is worse in the middle of the speech sounds than it is at either end.

The degree and shape of the hearing loss indicates how well your child can hear without hearing aids. A child with a mild flat loss can hear normal conversation in quiet situations when you are close by. A child with a moderate sloping hearing loss will hear talking when it is louder than normal. A child with a severe hearing loss with a cookie bite shape will be able to hear the TV if it is turned up very loudly. A child with a profound hearing loss will be able to hear very loud environmental sounds like the siren on a fire truck.

Any hearing loss will interfere with hearing the speech sounds and the development of speech and language skills.

A hearing loss is a decrease in the ear's ability to detect sound. A hearing loss may occur in one or both ears. A loss in one ear is classified as unilateral. A loss in both ears is classified as bilateral. Both can result from interference with any of the ear structures or brain pathways.

Children with a unilateral hearing loss can develop speech and language skills equal to a child without hearing loss. However, they may have difficulty hearing faint or distant speech and figuring out the direction of a sound in noisy environments. The higher the degree of hearing loss the more affect on speech and language development.

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Conductive Hearing Loss - When a baby has hearing loss, something is interfering with the path of the sound. Sometimes the problem is in the outer ear or in the middle ear. When this happens, the sound is too soft to be picked up by the cochlea. This is called a conductive hearing loss. A conductive hearing loss might occur if the ear canal is not completely open, or if the ossicles are not formed correctly. Sometimes conductive hearing loss can be improved by surgery. If surgery is not recommended, a hearing aid can usually be used to improve hearing.

Sensorineural Hearing Loss - In some cases, the hair cells in the cochlea are damaged and these damaged hair cells do not properly transmit sound information to the brain. The hearing loss is called a sensorineural hearing loss. Although it has also been called a "nerve loss" or "nerve deafness", these terms are technically incorrect because the damage involves the cochlea not the nerve. Amplification is the primary treatment for sensorineural hearing loss. Hearing aids are helpful for mild, moderate, or severe sensorineural hearing loss,with the treatment for profound hearing loss either hearing aids or cochlear implant.

Mixed Loss - Sometimes the hearing loss is a combination of both a conductive and sensorineural hearing loss. This is called a mixed loss. The treatment for a mixed hearing loss might include a combination of surgery and the use of hearing aids.

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The degree of hearing loss refers to the severity of hearing loss. For children, hearing is usually described by the average hearing level.

Normal Range or No Loss: - 0 to 15 dB

Slight Loss/Minimal Loss= 16 to 20 dB Mild Loss = 21 to 40 dB

Moderate Loss = 41 to 55 dB

Moderate/Severe Loss = 56 to 70 dB

Severe Loss = 71 to 90 dB Profound Loss = 91 dB or more

Normal hearing threshold is between 0 and 15 dB. A child with mild high frequency hearing loss will have trouble hearing and understanding soft speech, speech from a distance or speech with background noise. With moderate hearing loss the child will have difficulty with conversations, even at close distances. A child with a severe hearing loss may only hear very loud speech or other loud sounds.

Deaf vs. Hard of Hearing
You will hear both the terms: deaf and hard of hearing. Deaf is a term used to describe persons who have a hearing loss greater than 90 decibels. It may also be used to refer to those who consider themselves part of the Deaf community or culture and choose to communicate using American Sign Language. Hard of hearing is a term used to describe those who have a mild to severe hearing loss.

What are common symptoms of hearing loss in infants?
Your baby may have some degree of hearing loss if he/she shows the following behaviors:

• Does not startle, move, cry or react in any way to unexpected loud noises
• Does not awaken to loud noises
• Does not turn his/her head in the direction of your voice
• Does not freely imitate sound

What are common symptoms of hearing loss in toddlers?
Your child may have some degree of hearing loss if he/she shows the following behaviors:

• Inconsistent responses to sound
• Delayed language and speech development
• Unclear speech
• Turns up sound on TV, radio and cd player
• Does not follow directions
• Often says “Huh?”
• Does not respond when called

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