Hearing Evaluation

Hearing screening versus hearing evaluation

The difference between hearing screening and hearing evaluation can be confusing (Asha.org). A hearing screening is often a preliminary step to hearing (audiological) evaluation to see if further evaluation is required. Screening is a quick way to categorize an individual into a pass or fail group. Those who fail a screening need a more thorough assessment by an audiologist, utilizing a number of different tests.

Audiogram: Pure-tone audiometric testing

audiograhm2Pure-tone audiometry to obtain an audiogram is the basic portion of a hearing evaluation. An audiogram is a graph that shows the softest levels that can be heard audible at standardized frequencies as measured by an audiometer. The Y axis represents intensity measured in decibels (dB), and the X axis represents frequency measured in Hertz (Hz). Most audiograms cover a range of frequencies 250 Hz to 8000 Hz (8 kHz) because this range includes the major sounds of speech. The threshold of hearing is plotted relative to standardized data that represent normal hearing (dB HL). These hearing thresholds are not the same as thresholds measured in absolute terms of sound pressure level (dB SPL).

Speech testing

In addition to pure-tone testing, an audiological evaluation will typically include tests of speech understanding. The speech/spondee reception threshold (SRT/ST) is the softest level at which the patient can hear and repeat standardized 2-syllable words 50% of the time, and is helpful in confirming the pure-tone results. Word recognition tests performed at various audible intensity levels are also typically administered in quiet and/or noise to help determine how well a patient can discriminate speech at conversational levels.

Tests of middle ear function

The audiologist may perform tests to provide information about how the middle ear is functioning. These tests include tympanometry and measurement of acoustic reflexes. These are particular valuable in ruling out middle-ear problems and possible auditory nerve prolems as a component of a hearing loss. A small probe, which is connected to specialized equipment, is placed into the ear canal to make these measurements.

Otoacoustic emissions (OAEs)

OAEs are very faint sounds that are emitted by the outer hair cells of the inner ear (cochlea) and echoed back into the middle ear in response to sound stimulation. They are measured with specialized equipment through a small probe placed into the ear canal. OAEs are a sensitive measure of cochlear outer hair cell status, as they are typically present only when hearing is normal or near normal and are typically absent when there is conductive or cochlear hearing loss. OAEs can be helpful in assessing possible inner ear damage in tinnitus patients and patients with noise exposure, as abnormalities may appear prior to clinically significant changes measured with audiometry. They are also used as a part of newborn hearing screening and testing of young children or other difficult-to-test patients.

Auditory Brainstem Response (ABR) testing

The ABR is a specialized test that provides information about the cochlea (inner ear) and the auditory nerve pathways of the brainstem. Noninvasive electrodes are placed on the patient’s head, and waveforms are recorded with specialized equipment while the patient rests quietly or sleeps. The ABR is helpful for patients with signs or symptoms of disorders that may suggest an auditory problem beyond the cochlea in the brain pathways and also for the testing of newborns, young children, or other patients who have difficulty responding reliably on conventional audiometric testing. Should you need this type of testing, we will be happy to refer you to audiologists who provide this specialized testing.

Balance function evaluation

Dizziness is one of the most common medical complaints and affects 20-30% of the general population (ASHA.org). Symptoms may include unsteadiness, wooziness, disorientation, blurred vision, or vertigo (a sensation of the room spinning around you). Sometimes loud sounds or a change in position of the head or body will bring on or make the problem worse. Nausea, vomiting, and headaches may also accompany vertigo. Balance problems can be associated with many conditions, so a thorough evaluation may be warranted. A number of audiologists specialize in assessment of balance and falls disorders. A battery of tests is included in this assessment. If your symptoms include problems of dizziness, vertigo, or imbalance, we are able to refer you to audiologists who provide this specialized testing, as well as to physicians who evaluate and treat these disorders.

Degree of hearing loss

Degree of hearing loss refers to the severity of the loss. The table below shows a commonly used classification system. The numbers are representative of the patient’s hearing loss range in decibels (dB HL).

Degree of hearing loss

Hearing loss range (dB HL)

Normal

–10 to 15

Slight

16 to 25

Mild

26 to 40

Moderate

41 to 55

Moderately severe

56 to 70

Severe

71 to 90

Profound

91+

Source: Clark, J. G. (1981). Uses and abuses of hearing loss classification. Asha, 23, 493–500. Retrieved from http://www.asha.org/public/hearing/Degree-of-Hearing-Loss/.

Types of Hearing loss

Hearing loss can be categorized according to the part of the auditory system that is damaged: conductive, sensorineural, or mixed hearing loss (http://www.asha.org/public/hearing/Types-of-Hearing-Loss/).

Conductive hearing loss occurs when sound is not conducted efficiently through the ear canal to the eardrum and the middle ear bones (ossicles). Conductive hearing loss can often be treated medically. Possible causes include ear infection, fluid in the middle ear, poor Eustachian tube function, perforated eardrum, impacted ear wax (cerumen), benign tumors, presence of a foreign body, trauma to the ear, hereditary fusion of the middle ear bones, or absence or malformation of the outer ear, ear canal, or middle ear.

Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or the nerve pathways from the inner ear to the brain. This is the most common type of permanent hearing loss and typically cannot be medically or surgically corrected. The ability to hear soft sounds is reduced and, even when speech is made loud enough to hear, it may still sound muffled or unclear. Possible causes include genetic or hereditary factors, exposure to loud noise, degenerative changes from aging, head trauma, malformation of the inner ear, and drugs that are toxic to hearing.

Mixed hearing loss occurs when there is a combination of conductive and sensorineural hearing loss types.