An audiologist carries out a range of tests on adults and children to determine the presence, nature and extent of hearing loss and balance disorders, enabling accurate clinical diagnosis in a range of hearing related conditions. They quantify and qualify hearing in terms of the degree, the type and the configuration of the hearing loss.
Patients referred for evaluation, diagnosis and/or treatment receive a test battery that includes pure tone audiometry and/or immittance testing. When diagnostically indicated, further testing could include stapedial reflex thresholds and decay, speech audiometry and otoacoustic emissions. The extent of hearing loss and psychosocial disposition will determine further habilitation options (eg referral for hearing therapy).
Pure tone audiometry (PTA)
This test assesses your hearing sensitivity across a range of frequencies (pitches), which are involved in speech perception. It involves listening to sounds via headphones and responding by pressing a button every time a sound is heard. It usually takes approximately 20 minutes to complete. Audiologists quantify and qualify hearing in terms of the degree of hearing loss, the type of hearing loss and the configuration of the hearing loss.
With regard to degree of hearing loss, the audiologist is looking for quantitative information. Hearing levels are expressed in decibels (dB) based on the pure tone average for the frequencies 250 to 8000 Hz and discussed using descriptors related to severity:
- normal hearing (up to 20 dB HL)
- mild hearing loss (21 to 40 dB HL)
- moderate hearing loss (41 to 70 dB HL)
- severe hearing loss (71 to 95 dB HL)
- profound hearing loss (95 dB HL or greater).
With regard to the configuration of the hearing loss, the audiologist is looking at qualitative attributes such as:
- bilateral (both ears) versus unilateral (one ear)hearing loss
- symmetrical (same level/severity of hearing loss in both ears) versus asymmetrical hearing loss (different levels/severity of hearing loss in each ear)
- high-frequency/pitched versus low frequency/pitched hearing loss
- progressive versus sudden hearing loss
- stable versus fluctuating hearing loss.
After assessment/diagnostic procedures are complete, the option of hearing aid amplification is discussed with the patient if necessary. The final decision as to the type of hearing aid fitted is based on an audiological assessment of the patient’s individual suitability.
Tympanometry and stapedial reflexes (immitance testing)
This is a quick objective test used to assess middle ear function. It involves placing small plugs in the ears which record middle ear pressure. This may include listening to some loud noises for a few minutes in order to measure the reflex of the muscles in the middle ear.
Otoacoustic emissions (OAES)
This is a valuable objective test that assesses hair cell function in the cochlea (hearing organ in the inner ear). It involves listening to a clicking sound or a combination of two tones for a few minutes. The results are recorded automatically using computer software.
This is a diagnostic test that assesses speech discrimination using single words. It involves listening to words and repeating what was heard to the audiologist who records the results. It takes approximately 30 minutes to complete.
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