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The Audiogram Explained, At Last!

By: MELANIE SISSON, AU.D., CCC-A
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Does an audiogram show test results that help you make sense of hearing loss, or is it a confusing series of lines and circles that leaves you frustrated? Audiograms are not as complicated as they look if you know what you're looking at. And you will by the end of this article. Let's start with some details about what to expect when you or your child has a hearing test and what those results tell you and your hearing healthcare professional about hearing loss. Finally, let's look at how this information helps you both best decide what the next steps should be.

Types of Hearing Loss

When we hear, the outer ear collects sound, the middle ear transmits it and the inner ear passes it on to the brain. The inner ear, which consists of the hearing organ (the cochlea) and the hearing nerve (cranial nerve VIII), introduces an electrical signal to the brain, which processes sound into comprehensible information. A problem in the outer or middle ear that prevents sound from reaching the inner ear is called conductive hearing loss. Factors that can cause conductive hearing loss include ear infection, fluid in the ear, a hole in the eardrum and blockage as a result of excess earwax. Conductive hearing loss is usually temporary and can last a few days, several weeks or even a number of months. It can also improve or get worse. The amount of hearing loss, the length of time the hearing loss persists and how it changes all depend upon what is causing the conductive hearing loss.

Sensorineural hearing loss is caused by damage to the inner ear most often involving the hearing organ and rarely affecting the hearing nerve. The hearing organ is shaped like a snail shell and is filled with fluid and tiny hair cells. The hearing nerve is part of the central nervous system and transmits sound to the brain. In some cases, sensorineural hearing loss may get worse over time, but it is unfortunately most often lifelong and cannot be corrected in one visit to the doctor.

Mixed hearing loss is a combination of conductive and sensorineural hearing loss. Since conductive hearing loss can be temporary, someone with sensorineural hearing loss may experience a short-term decline in hearing due to a conductive problem, but that is usually quite easily rectified.

Now that we have the basics under our belt, let's find out what normally happens on the first visit to have your hearing tested.

The Actual Test

Hearing tests are conducted in a sound-proof booth. You, or you and your child, will sit inside and the hearing healthcare professional will sit outside the booth, on the other side of a window. Testing for adults and children older than fi ve involves wearing earphones or ear inserts (like an MP3 player's small earbuds), listening for soft tones and raising a hand or pressing a button when you hear them. This type of testing is called air conduction testing, meaning that tones are emitted from the earphone and travel through the air to reach the eardrum. The results are plotted on a graph called an audiogram.

A game can be used to test young children, who may or may not wear earphones or ear inserts. Parents are usually asked not to do anything while their child is tested so that they do not cause their child to appear to be responding to a sound when he or she is really responding to the parent. If your child becomes upset during testing you could soothe her as you would in any other context.

Along with air conduction testing, older children and adults repeat words and undergo tests to check eardrum movement, among other possible assessments.

A test that can help identify what type of hearing loss a person has is a bone conduction test, results of which are also plotted on the audiogram. This involves placing a small box, called a bone oscillator, behind the ear or on the forehead, held in place by a headband. The oscillator vibrates the bones of the skull, which is not painful. When the bones vibrate, sound goes straight to the inner ear, bypassing the outer ear and the middle ear. As with a normal hearing test, you are asked to listen for soft tones created by the oscillator and respond when you hear them.

When the bones vibrate, both the right and left inner ears, or cochleae, hear the tone at the same time. What is often necessary, though, is to test each inner ear individually so that only one inner ear at a time hears the tone. In order to do this, a technique called "masking" is employed. The cochlea of the ear wearing the bone oscillator is tested while the other ear hears static through a headphone or ear insert to stop that ear from hearing the tone.

Don't worry none of the tests are painful.

Reviewing the Results

The audiogram is a graph that plots the hearing test results which reveal how well you hear a range of pitches, particularly those most common in speech. The audiogram helps hearing healthcare professionals decide what the best next step is, such as how much amplification a hearing aid needs to provide.

Across the top of the audiogram, a normal range of hearing is displayed. If your results are graphed in that range, your hearing is normal.

Down the side of the graph labeled "Hearing Threshold" is the measurement of volume in decibels
(dB), with lower numbers representing softer, harderto-hear sounds, such as a pin drop, and higher numbers representing something loud like a rock band concert.

Across the top of the graph, the audiogram displays pitch (Frequency), measured in hertz (Hz). Lower
numbers represent lower pitches, like a foghorn or bass drum, and higher numbers represent higher pitches, such as the chirp of a small bird or the whistle of a tea kettle (see Fig. 1).

The very softest sound you are able to hear at any given pitch is called your hearing threshold. In other
words, a threshold is the volume at which you begin to hear a certain pitch. Thresholds in air conduction testing are graphed using "X" and "O", with X always representing the left ear and O always representing the right ear.

Detecting thresholds on a small child can be tricky because movement and even breathing can interfere with accurate results. When testing is new to a young child, it will likely be minimal response levels that are noted. As the child gains practice with the testing, thresholds will more likely be obtained. Often early testing of infants and young children will give only a general idea of hearing levels and type of hearing loss. It can take some time and a few test sessions to get a complete picture of a young child's hearing levels for all pitches. Treatment can begin based on the general idea of a young child's hearing loss while still working to more accurately define the audiogram.

The softest sounds you could hear during the bone conduction test appear on the audiogram as a pointed bracket symbol, "<" or ">", when the results are for both ears. No matter the direction (to the left or the right), the pointed bracket shows the response from both inner ears working together. Results for just one inner ear are graphed with a straight bracket, "[" or "]", representing the left or the right inner ear.

If these bone conduction bracket symbols are above your Xs and Os on the graph, then hearing loss is all or partly conductive. This indicates that your inner ear is hearing better than the outer, middle and inner ear working together but something in the outer or middle ear is blocking hearing (see Fig. 2). Recall that conductive hearing loss can be temporary and can get better or worse over time. Your hearing healthcare professional will want to monitor a conductive loss by doing audiograms on different days. Changes would be evident if air conduction symbols (X and O) were at a higher or lower point on a newer audiogram when compared with the older one. If symbols on the new audiogram are closer to the top of the graph than the symbols on the old one, your hearing has improved since the last test. If the symbols are lower on the more recent audiogram, as compared to previously, then hearing has worsened since the last test.

If the bracket symbols match up closely with the Xs and Os on your audiogram, then your hearing loss is sensorineural, that is, based in the inner ear, not the middle or outer ear. As mentioned previously, sensorineural hearing loss is not likely to improve. A decrease in sensorineural hearing (or cochlear/ inner ear function) from one test day to another would be apparent on an audiogram if the bone conduction symbols (<, >, [, ]) were moving further toward the bottom of a more recent audiogram when compared to a prior audiogram. If hearing loss is not a mixture of sensorineural and conductive hearing loss, the Xs and Os would also move downward on a newer audiogram. This is because results for all three parts of the ear the outer, middle and inner ears are indicated by the Xs and Os.

Once you have your audiogram in hand, your hearing healthcare professional can discuss follow-up options. In some cases, such as with conductive hearing loss, you may need to see a doctor to
address the cause of the conductive portion of the hearing loss. If the cause of the hearing loss cannot be treated, you may wish not to take any immediate action, but rather wait to see if hearing loss gets worse or look into options for hearing aids or cochlear implants. This will depend on the type of hearing loss, amount of hearing loss and your personal preferences. Follow-up options may be different for adults versus children, whose language development is enhanced by good hearing ability.

It is important to schedule regular audiograms with your hearing healthcare professional to check for possible further changes in your hearing. The plan for retests will be put together by your hearing healthcare professional and will depend on your age and type of hearing loss.

Audiograms do not provide the whole picture of a person's hearing loss. For example, they do not show how successfully you function in your daily listening environments. When you are talking with people, you use many other cues to help you communicate, such as body language, gestures, lip movements and facial expressions, as well as context provided by the topic and meaning of the conversation. Each person is unique. Even if two people have the exact same audiogram, the effects of hearing loss, the amount of success with listening and communication and the amount of success with amplification (hearing aids, cochlear implants, etc.) will be unique.

Audiograms help you and your hearing healthcare professional to decide what, if anything, should be done to make sound more usable for you. Audiograms also help you to see if hearing is getting better or worse by testing at different times. They do not define what life with your hearing loss will be like. That is up to you, with some help from your friends, family and your hearing healthcare professional.

Time to Get Your Hearing Tested?

If you answer "Yes" to two or more of the following questions, you should make an appointment with a hearing healthcare professional:
- Are you having trouble hearing the television set?
- Are you having difficulty hearing on the telephone?
- Are you having difficulty hearing the doorbell, telephone, clock or other devices?
- Do you feel that people "mumble" and don't speak clearly?
- Do you frequently ask other people to repeat themselves?
- Do you feel like your hearing is "cloudy" or "not clear"?
- Do other people ask you if you have problems hearing?
- Do you hear people, but just don't quite make out what they are saying?
- Do you find yourself avoiding situations because you are not able to hear other people properly?
- Do you find that your hearing is not what is used to be?

According to the National Institute for Occupational Safety and Health, "Anyone regularly exposed to hazardous noise should have an annual hearing test. Also, anyone who notices a change in his hearing (or who develops tinnitus) should have his ears checked. People who have healthy ears and who are not exposed to hazardous noise should get a hearing test every three years."
Source: Home Audiology Services, East Moriches, N.Y., www.homeaudiologyservices.com

If You Do Get Hearing Aids

- Daily maintenance can keep hearing aids working properly for as long as five to seven years. Experts recommend taking the hearing aids off each day and wiping them with a soft cloth or tissue. Many devices come with a brush or wire pick to remove earwax from the hearing aid. Or with Jodi Consumer Vac (www.jodivac.com), you can get the same kind of hearing aid vacuum cleaning the professionals use to remove wax. It's also a good idea to remove the batteries and leave the battery compartment door open, both to prolong battery life and to allow moisture to dissipate.
- Next, store hearing aids in an electronic dry-aid kit like those manufactured by TransEar (www.eartech.com). These kits normally feature a germicidal light that kills bacteria and other germs. And the kits' fans circulate air around the hearing aid, while desiccants absorb moisture to ensure that the device stays dry.
- It helps to keep the ears clean too. Wax is productive for ears, but too much is problematic for both hearing and keeping a hearing aid working properly. Health Enterprises Ear Irrigator (www.healthenterprises.com) features a saline solution and clinically tested "tri-stream" tip with a pressure-control bottle. It can be used up to three times a week to clean ears and prevent damaging earwax buildup. Consult a physician before cleaning your own ears for the first time.
- According to Brendan Leonard, president of Health Enterprises, "Research indicates that 75 percent of all hearing aid repairs are due to earwax and moisture and almost 100 percent of these repairs are preventable with proper maintenance." For repairs that can't be prevented, there's the protection of a hearing aid warranty, which can be purchased separately from companies like SoundAid (www.soundaid.com).

Hearing Loss Help offers a comprehensive description of a complete audiological evaluation, including word recognition testing, uncomfortable loudness level testing, most comfortable listening level testing, tympanometry and acoustic reflexes. Visit www.hearinglosshelp.com/articles/hearingtesting.htm.

Melanie Sisson, Au.D., CCC-A, is associate director of clinical trials at Pfizer, Inc. and a practicing pediatric audiologist at Lawrence & Memorial Hospital in New London, Conn. She is the author of the Workbook for Parents of Children who are Newly Identified as Hard of Hearing, published by Oticon Pediatrics. Contact her at melanie.sisson@pfizer.com. To obtain a copy of the workbook, contact Oticon Pediatrics at 888.OTI.PED1 (888.684.7331).