Audiometry Test (Pure Tone Audiometry and Speech Audiometry, Vestibular Evoked Myogenic Potential)

Norm of Audiometry Test (Pure Tone Audiometry and Speech Audiometry, Vestibular Evoked Myogenic Potential)

Adult	0–25 dB HL hearing sensitivity
Child	0–15 dB HL hearing sensitivity
Word-discrimination score	Client is able to spoken words with 90% accuracy
VEMP	Positive steady results

 

Usage of Audiometry Test (Pure Tone Audiometry and Speech Audiometry, Vestibular Evoked Myogenic Potential)

Delineation of type and amount of hearing loss (that is, conductive, sensorineural, or mixed), rehabilitation monitoring post cochlear implant or post stapedectomy, diagnosis of glue ear (otitis media with effusion). Vestibular evoked myogenic potential (VEMP) is used to help evaluate clients experiencing symptoms of dizziness and/or suspected of having vestibulocochlear disorders, as well as to help differentiate sudden deafness from the beginning stage of Ménière's disease. Higher peak amplitudes (VEMP) are seen in clients with endolymphatic hydrops or multiple sclerosis and in clients with distended saccular hydrops seen in the early stage of Ménière's disease.

 

Description of Audiometry Test (Pure Tone Audiometry and Speech Audiometry, Vestibular Evoked Myogenic Potential)

Pure tone audiometry is a hearing test using an audiometer that sends tones into the client's ear and vibrations through the bone. It measures the frequencies at which the client is able to hear 50% or more of the tones. The test is able to detect defects in air conduction (conductive hearing loss) through the use of tones or defects in air and bone conduction (sensorineural hearing loss) through the use of vibrations to help identify the amount and type of hearing loss present. Speech audiometry is a hearing test that determines the client's speech-reception threshold and word-discrimination score by measuring the number of words the client can repeat after they are heard when delivered through earphones at precise decibel intensities. Speech audiometry helps differentiate between conductive and sensorineural hearing loss. Vestibular evoked myogenic potential is a reflex conducted via the inferior vestibular nerve that indicates the integrity of the vestibular response. Measurement is performed via skull taps with recording of resultant muscular responses.

 

Professional Considerations of Audiometry Test (Pure Tone Audiometry and Speech Audiometry, Vestibular Evoked Myogenic Potential)

Consent form NOT required.
Preparation

1. See Client and Family Teaching.
2. Ensure that the external auditory canal is free of impacted cerumen.
3. Obtain an audiometer, earphones, a vibrator for bone-conduction testing, and an otoscope.

 

Procedure

1. A plastic tube may be inserted into the external auditory canal to maintain the canal's patency during testing with earphones.
2. The earphones are placed over the ears and fastened in place.
3. A preliminary tone is demonstrated for the client to become familiar with the test.
4. The ear not being tested is masked with audiometer noise to prevent crossover interference and subsequent inaccurate estimation of hearing loss.
5. Air conduction testing: The better ear is tested first. The client is instructed to give a signal each time a tone is heard. Starting with 1000 Hz, tones are delivered to the ear, decreasing by increments of 10 dB until a negative response is obtained. Tone levels are then increased in smaller increments and then decreased until the air conduction threshold level is obtained. The air conduction threshold level is the lowest hertz level at which the client is able to hear two out of three tones. This procedure is then repeated several times, starting with a different tone level each time (such as 2000, 4000, 8000, 1000, 500, and finally 250 Hz). The second ear is then tested in the same way. Finally, retesting is performed on each ear to determine test/retest reliability. Acceptable variation for retesting for each ear must be within 5 dB above or below the initial test result. Graphic recordings are made of the threshold levels.
6. Bone conduction testing: The better ear is tested first. After removal of the earphones, the bone conduction vibrator is held on the mastoid process of the ear. Starting from 250 Hz, tones are delivered to the ear, with decrements at 10 dB until a negative response is obtained. Tone levels are then increased in smaller increments and then decreased until the bone conduction threshold level is obtained. The bone conduction threshold level is the lowest hertz level at which the client is able to hear two out of three tones. This procedure is then repeated several times, starting with a different tone level each time (500, 1000, 2000, and finally 4000 Hz). The second ear is then tested in the same way. Finally, retesting is performed on each ear to determine test/retest reliability. Acceptable variation for retesting for each ear must be within 5 dB above or below the initial test result. Graphic recordings are made of the threshold levels.
7. Speech reception threshold measurement: Two-syllable, familiar, spoken words are delivered through the earphones. The client is asked to repeat each word. The speech reception threshold is the decibel level at which the client is able to restate correctly at least half the words.
8. Word discrimination score: One-syllable, familiar, phonetically balanced words are delivered through the earphones at 30 dB higher than the client's own speech reception threshold. The client is asked to repeat each word. Clients with conductive hearing loss will have a normal word discrimination score. Those with sensorineural hearing loss will have a lower than normal score.
9. Amount-of-hearing-loss calculation: The amount of hearing loss, called the “pure tone average” (PTA), is calculated by averaging the air conduction threshold levels. Mild hearing loss demonstrates a PTA of 26–40 dB. Moderate hearing loss demonstrates a PTA of 41–55 dB. Moderately severe hearing loss demonstrates a PTA of 56–70 dB. Severe hearing loss demonstrates a PTA of 71–90 dB. Profound hearing loss demonstrates a PTA of >90 dB.
10. Type-of-hearing-loss calculation: The type of hearing loss is interpreted by examination of the relationship between the air conduction threshold levels and the bone conduction threshold levels at the different frequencies. In sensorineural hearing loss, both thresholds are depressed to about the same degree. In conductive hearing loss, only the air conduction thresholds are depressed. In mixed hearing loss, both thresholds are depressed, but air conduction threshold levels are more depressed than bone conduction threshold levels.
11. Vestibular evoked myogenic potential: Skin electrodes are placed over both sternocleidomastoid muscles. Light skull taps over each ear and on the middle of the forehead are manually applied. Alternatively, loud clicks are produced externally to each ear. The responses evoked by these taps that travel through the sternocleidomastoid muscles are measured through the electrodes and recorded as waveforms.

 

Postprocedure Care

1. Cleanse the earphones and otoscope with antiseptic.

 

Client and Family Teaching

1. Stay in an environment free of extremely loud noises for 16 hours before the test.

 

Factors That Affect Results

1. Testing should be performed in a very quiet environment for the most accurate results.
2. The client should not be able to see the examiner because changes in tone level are made. Signals should be delivered in a nonrhythmic pattern.
3. The client must be able to distinguish between the pure tones and tinnitus or vibrotactile stimulation.
4. Test/retest differences of more than 10 dB may be caused by unreliable equipment.
5. The use of plastic tubes to maintain external auditory canal patency should be noted on the audiogram.
6. Low levels of serum estradiol can impede hearing sensitivity in pure tone audiometry results in postmenopausal women.

 

Other Data

1. See also Acoustic immittance tests.
2. There is higher prevalence of hearing impairment in persons with diabetes, cognitive impairment, or low education levels or in those who use alcohol or smoke.