Diagnostic hearing test
Diagnostic hearing tests are used to examine the outer, middle and inner ear. These tests determine if there is hearing loss and where it is occurring along the hearing pathway. Each test also allows for a check and balance to make sure results are accurate. By establishing the type of hearing loss present, audiologists and other specialists can determine the best treatment options.
Otoscopy
The first step for any hearing exam is otoscopy. Otoscopy is a clinical procedure used to examine the structures of the ear, particularly the external auditory canal, tympanic membrane, and middle ear. By visualising the ear canal and ear drum, the examiner can check for wax occlusion, foreign objects, ear infections and inspect the eardrum for any issues.
Air conduction testing
Air conduction exams test the whole hearing system at once. Headphones are either placed on or over the ear (or insert earphones are placed into the ear canal) so the person being tested can hear the sounds. The sound wave travels though the outer ear canal, into the middle ear space, and into the inner ear organ - the cochlea - where the sound wave is converted into an electrical signal the brain can understand.
When the sound is presented, the patient is required to respond. Usually, the examiner will have the patient raise their hand or press a button when they hear the sound. For a diagnostic exam, a series of frequencies/tones are presented at different intensity levels to determine the softest sound the patient can hear.
Low, mid, and high frequency sounds are presented; the most common are 500, 1000, 2000, 4000 and 8000 Hz. The inter-octave tones, 750, 1500, 3000 and 6000 Hz are also tested, particularly if a large difference is seen from octave sounds. Sometimes, especially when looking for damage from drugs that are ototoxic, higher frequencies up to 10,000-20,000 Hz are also tested.
It is important to remember that an Air Conduction test can only determine if there is hearing loss, it cannot say where the hearing loss is occurring.
Bone conduction testing
Bone Conduction testing allows us to determine whether the hearing loss is in the outer, middle or inner part of the ear. A small vibrator, called a bone oscillator, is placed on the bone behind the ear or on the forehead. Sounds are presented through the oscillator onto the bone and go directly to the cochlea bypassing the outer and middle part of the ear.
Bone conduction testing allows an audiologist to determine whether the hearing loss present is conductive, sensorineural or mixed. A conductive hearing loss occurs when there is an issue in the outer or middle ear. Some examples of conductive hearing loss are wax occlusion, hole/perforation of the ear drum, or a middle ear infection.
A sensorineural hearing loss transpires when there is damage to the hearing organ/cochlea or the nerve to the brain, such as noise induced hearing loss or age-related hearing loss. A mixed hearing loss has components of both conductive and sensorineural hearing loss.
Speech testing
A comprehensive exam requires speech testing. Speech testing allows the examiner to see how a patient hears speech and how they respond. There are many different speech tests, the most common speech test performed in a diagnostic exam is the Speech Reception Threshold (SRT) and Word recognition testing. Speech testing can be performed using the examiners’ voice or with recorded material. Recorded material is the gold standard, as it allows for more controlled, consistent, and accurate testing.
SRT tests determine the softest level of speech that someone can hear and repeat the word back correctly. This test can only be done with children and adults who are able to speak. Of course, if the patient is unable to repeat the words back, different tests can be performed; for example, Speech Detection Testing (SDT) where the patient can raise their hand or press a button when they hear the word rather than repeating the word back.
Word recognition testing is used to see how well someone hears and understands speech at a level that should be easy for them to hear. A sentence or carrier phrase is used (“Say the word ______”) and the patient is required to repeat the word. So, for example: “Say the word hello”, and the patient would repeat “hello”. Sometimes word recognition testing will be done at a very loud level, for example 90 dB, to determine if a retrocochlear pathology is present.
Diagnostic audiometers
It is essential to ensure a thorough diagnosis of the cause and type of hearing loss before being able to select the right treatment. Amplivox has developed a suite of innovative and user-friendly diagnostic audiometers which perform a wide range of hearing loss tests, including AC, BC, speech and special tests: ABLB, Stenger, SISI, Tone decay, HLS, MHA.
For more information on our range of diagnostic audiometers, please visit our audiometers webpage, contact our customer support team on +44 (0)1865 880 846 or email.
References
Centers for Disease Control Prevention (2018). National Institute for Occupational Safety and Health (NIOSH). Accessed at:
https://www.cdc.gov/niosh
Centers for Disease Control Prevention (2022). Preventing Noise-induced hearing loss. Accessed at:
https://www.cdc.gov/hearing-loss/prevention