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What is an Audiogram?
An audiogram is a graph of your hearing created during your hearing test (See Figure). The various frequencies (pitches) that are tested are displayed across the top of the graph. The vertical numbers along the side represent the softest level of hearing at each pitch in dB (decibels, which is the unit of measurement for hearing). Circle symbols correspond to the right ear and "X" symbols correspond to the left ear. The arrows or symbols that look like staples signify bone conduction scores. Test pitches are arranged with lower pitches to the left and higher pitches to the right (going up in frequency from left to right). The vowel sounds of speech are typically low frequency sounds that make up the loudness of speech. The consonant sounds like "F", "S", "Th", and "Z" are high frequency sounds and provide meaningful information about speech such as indicating possession or whether a word is plural and help us distinguish one word from another (hit versus hip). Speech is made up of a wide range of dynamic (constantly changing) frequencies, rather than just one pitch.
Hearing Tests for Adults and Older Children
Pure Tone Audiometry
Pure tone testing is accomplished by having the patient listen through headphones, insert earphones or sometimes through loudspeakers in a special, quiet room called a sound booth. The patient is instructed to indicate when tones are heard. The softest level that a patient consistently hears is called a hearing threshold. Threshold results are marked on the audiogram as either an X or an O (see above). This type of testing helps to determine the amount or degree of hearing loss.
Bone Conduction Audiometry
Bone conduction testing is accomplished by placing a special bone vibrator type of headphone behind the ear on the mastoid bone. Thresholds are again measured. This method of testing bypasses the middle ear and tests the hearing of the inner ear (cochlea), indicating whether the hearing loss is conductive, mixed or sensorineural.
Speech testing does not seek to assess how well a person can talk or speak, but rather to determine how well speech is understood. There are two basic speech tests usually administered. The first is called a Speech Recognition Threshold (SRT) or a Speech Awareness Threshold (SAT). This involves determining the softest level at which speech is understood (SRT) or heard (SAT). To obtain an SRT patients are asked to repeat two-syllable words such as baseball, hotdog and cowboy. To obtain an SAT the patient is asked to indicate the softest level at which speech is heard, regardless of whether or not what is said is understood.
The second typical speech test is usually called Speech Discrimination Testing and it evaluates word understanding. A list of one-syllable words is presented at a particular level (frequently at the person's most comfortable listening level) and a percentage score is obtained. This helps assist the audiologist in predicting how well a patient might do with hearing aids.
Tympanometry consists of measuring the pressure in the middle ear. There are three main types of tympanogram results:
• TYPE A: Normal middle ear function (looks like a peak or a mountain).
• TYPE B: Abnormal middle ear function (looks like a flat line and is typically indicative of fluid or ear infection, a hole in the ear drum or it can indicate an open, normally functioning pressure equalization tube).
• Type C: Negative middle ear pressure (the "mountain" or peak is significantly shifted to the left, suggesting Eustachian tube dysfunction).
Hearing Tests for Infants and Babies
Very young infants are typically tested using Otoacoustic Emissions (OAE) or Auditory Brainstem Response testing (ABR). These two types of testing require no active participation from the baby. If either of these tests is needed, our Audiologists will explain the test in detail. Older infants are tested in the soundfield and behavioral responses to sound presentation are observed and compared to normal level responses according to their developmental age. This type of testing is called Behavioral Observation Audiometry (BOA) or Visual Reinforcement Audiometry (VRA). If behavioral testing suggests a hearing loss, OAE and ABR are used to confirm the results and help determine the type and amount of hearing loss.
The State of Arkansas' Universal Hearing Screening Program mandates that birthing hospitals screen infants' hearing prior to hospital discharge. Infants who fail the initial screening are referred to area audiologists for re-screening. Arkansas Center for Ear, Nose, Throat and Allergy developed the screening program at Sparks Regional Medical Center, which began in 1997, and we continued to run this program through 2000. We continue to provide this service for many area infants who do not receive or do not pass hospital-based screenings, as well as comprehensive audiologic follow-up for infants who fail screenings.
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