The Audiology Offices provides audiology diagnostic services to patients of all ages. Determining the type and degree of a patient’s hearing loss is crucial in order to develop their individualized treatment plan.
Pure tone audiometry
This test is used to determine the faintest sounds a patient can hear at a variety of frequencies. The patient will be seated in a sound booth and asked to wear specially designed headphones. Each time the patient hears a tone through the headphones they would press a buzzer or raise their hand.
The softest sound the patient can hear is called a threshold. A threshold is determined in each ear for low (250 Hz) and high (8000 Hz) frequencies. The results are then plotted on an audiogram, which is a visual representation of a patient’s type, degree and configuration of hearing loss.
This test can be performed on patients over the age of five; anyone younger may require play-like activities to indicate responses. Headphones are not used for these tests; instead, the sound is broadcast through speakers within the sound booth. This eliminates the ability to differentiate between unilateral and bilateral hearing loss.
Visual reinforcement audiometry can be used on children between six months and two years of age. The child is trained to look toward the sound source. Every time they correctly complete this task they are rewarded with a visual reinforcement, such as watching a toy move or a flashing light.
Conditioned play audiometry is appropriate for children two to five years old. When they hear a sound they are trained to perform an activity, such as putting a block in a box or placing a peg in a hole.
Pure-tone bone conduction testing is used to help determine the patient’s type of hearing loss. A bone conductor is placed behind the patient’s ear. The conductor creates a vibration which is passed through the bone, directly into the inner ear. The results are then compared to those of the pure-tone testing, which uses air to pass audible sound through the outer and middle ear before it reaches the inner ear. The difference between the two tests is called the air-bone gap.
Conductive hearing loss is caused by an issue with a patient’s outer or middle ear. This type of hearing loss is usually only temporary and can be medically or surgically treated. Patients with this type of hearing loss will show normal results on their bone conduction test but will score more than 10 dB worse on their pure-tone test.
Sensorineural hearing loss is caused by a problem in the inner ear. This type of hearing loss is usually permanent but can be managed with use of a hearing device. Individuals with this type of hearing loss will score within 10 dB of each other on both air and bone tests.
Mixed hearing loss is a combination of conductive and sensorineural. Patients with this type of hearing loss will have a problem with their outer or middle ear as well as a problem with their inner ear.
There are a variety of tests that use speech signals to evaluate hearing. These tests are used to determine the patient’s speech reception threshold (SRT), speech detection threshold (SDT) and ability to hear and understand everyday speech.
An SRT measurement is used to determine the the lowest level at which a patient can identify speech. A list of spondaic words, two-syllable words with equal stress on each syllable, are used for this measurement. These words are presented as either live speech or via a CD player. The patient must then repeat the words back to the examiner.
An SDT measurement is used to obtain the lowest level at which speech can be detected. Unlike an SRT measurement, patients are not required to repeat the words back to the tester; they only need to indicate when speech stimuli are present.
Sentence testing is able to evaluate a patient’s ability to hear and understand everyday speech. A number of tests have been developed using sentence identification as a test item. These tests can vary in sentence complexity and may be completed in several different listening environments.
This is an objective test used to determine how well the middle ear is functioning. The patient is seated and a small rubber tip is inserted into the entrance of their ear canal. This pushes air pressure into the ear canal. A graph called a tympanogram is created, which measures the movement of the patient’s eardrum and middle ear function. This information can be used to determine if there is fluid in the middle ear, a malfunction of the ossicular chain (bones in the middle ear), a perforated eardrum or a stiff eardrum.
Acoustic Reflex Testing
Acoustic reflex testing is used to determine how well a patient’s middle ear is functioning. An acoustic reflex is the response of the small muscles in the middle ear when exposed to a loud sound. The volume level at which the acoustic reflex occurs is used to confirm the results from the other hearing tests.
Otoacoustic Emissions Evaluation
Otoacoustic emissions (OAEs) are the almost inaudible sounds made by the outer hair cells that line the cochlea in response to noise. The patient is seated and asked to remain still throughout the whole test. A small probe, which contains a speaker that generates sounds and a microphone that can pick up the echo of the OAEs, is inserted into the ear canal. A series of sounds is broadcast through the probe.
If OAEs are not detected this could indicate a blockage in the outer ear canal, fluid buildup in the middle ear or damage to the outer hair cells within the inner ear.