Audiological evaluation procedures:
Tympanometry and acoustic reflexes:
These procedures evaluate the middle ear function by measuring the tympanic membrane compliance, the external ear canal volume, and the pressure changes inside the middle ear cavity, as well as the function of the middle ear muscles. These tests usually reveal middle ear infection, tympanic membrane stiffness or perforation, and abnormalities in the function of the middle ear muscles.
Visual reinforcement audiometry (VRA):
This hearing test is designed to evaluate the hearing of children from 6 months to two-years of age in a sound treated booth. The test includes the presentation of individual tones at different frequencies and intensities, from different directions inside the room. Children tend to search for the sound source by turning their heads or eyes toward the loudspeaker that produced the sound. After the child turns toward the sound source, the examiner displays a dancing toy or a cartoon as a reinforcement to encourage the child to continue searching for the sound source every time the sound is heard during the test. The child’s head or eye turn toward the sound source is considered as the child’s response to the heard sound.
This test evaluates the hearing of children from two to five years of age in a sound treated booth. During this test, the examiner presents several individual tones at different frequencies and intensities through the headphone or the loudspeaker. Each time the sound is presented, the child responds if he hears the sound by doing a certain task in a game context such as throwing a cube inside a bucket each time the child hears the sound. The child’s response to each sound allows the examiner to evaluate the child’s hearing level.
This test evaluates the hearing level of adults in a sound treated booth. In pure tone audiometry, the examiner presents several individual tones at different frequencies and intensities through the headphone mounted on the patient’s ears. The patient is instructed to push a button or raise his hand every time he hears the sound, allowing the examiner to identify the patient’s hearing level. In speech audiometry, the examiner presents several standardized words, and the patient is instructed to repeat the words as heard. This test allows the examiner to identify the patient’s speech reception threshold, and the word recognition score.
Otoacoustic Emissions Testing(OAE)
This test is used to evaluate the health of the OHCs within the cochlea by recording the OHCs emitted sounds in the external auditory canal. During this test, a small probe is place in the ear and clicks or tones are played and sent from the probe speaker to the ear canal, through the middle ear, and into the cochlea. Outer hair cells in the cochlea become excited and react by generating and emitting an acoustic response. This emitted response then travels in a reverse direction from the cochlea back to the ear canal, where it is detected by the probe microphone.
These are tests which determine the functioning of the middle ear. It only takes from 3 to 30 seconds per ear. It may also be referred to as Immittance Testing, which includes tests called (a) Tympanometry, and (b) Acoustic Reflexes. In this type of evaluation, eardrum mobility is measured under different pressure conditions to determine if any problems exist in the middle ear.
Auditory Brainstem Response (ABR)
During this test, three small electrodes are placed on the baby’s head, and then clicks or tones are played into little headphones placed over the baby’s ears. The equipment measures the brain’s response to these sounds. This test does not measure what the baby can hear, rather it determines the sounds to which the brain actively responds. This test takes only a few minutes and can be done while the baby is sleeping.
Pure-tone audiometry is a behavioral test used to measure hearing sensitivity. This measure involves the peripheral and central auditory systems. Pure-tone thresholds (PTTs) indicate the softest sound audible to an individual at least 50% of the time.
Audiometry for children involves the use of a sound-treated room in which a child is presented with a variety of sounds from high to low pitches, and from soft to loud intensity. An audiologist will have the child respond to the different sound and document it. A young child can be taught to turn to a sound (behavioral testing), or to place a toy on a box or a ring on a post (play audiolmetry).
The audiogram is a graph showing the results of a pure-tone hearing test. It will show how loud sounds need to be at different frequencies for you to hear them. The audiogram shows the type, degree, and configuration of hearing loss.
When you hear a sound during a hearing test, you raise your hand or push a button. The audiologist will make a note of how loud the sound was at each frequency. At the end of testing, the audiogram will show what you heard.
Pitch or Frequency
Each line that runs from left to right shows a frequency in Hertz, or Hz. The lowest pitches are on the left side and the highest pitches are on the right side. The frequencies tested are 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 3000Hz, 4000 Hz, and 8000 Hz.
Examples of “low-frequency” sounds are a rumble of thunder, a tuba, and sounds like the “oo” in “who.”
Examples of “high-frequency” sounds are a bird chirping, a whistle, and the “s” sound in “sun.”
Loudness or Intensity
Each line from top to bottom shows how loud the sound is in decibels, or dB. Lines at the top of the chart are for soft sounds. Lines at the bottom of the chart are for loud sounds.
Examples of soft sounds are a clock ticking, a person whispering, and leaves rustling.
Examples of loud sounds are a lawnmower, a car horn, and a rock concert.
The audiogram shows the pattern of your hearing loss. It also shows how severe it is, called the degree of hearing loss. For example, your hearing might be normal for low pitches but not for high pitches. In this case, you might hear speech, but it would not sound clear. If you have hearing loss at all pitches, you might have problems hearing any speech.
The audiologist marks what you hear in your right ear with a red O. What you hear in your left ear gets a blue X. If the Xs and Os are at the top of the graph, your hearing is normal. You have a hearing loss if the Xs and Os are farther down the graph .