Diagnostic hearing tests are employed to examine the inner, middle, and outer ear. The purpose of these tests is to determine the presence of hearing loss and its location of occurrence along the hearing pathway.
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By determining the type of hearing loss, audiologists and other specialists can determine the most effective treatment options.
Otoscopy
Otoscopy is the first step in any hearing exam. It is a clinical procedure used to visually inspect the structures of the ear, specifically the external auditory canal, tympanic membrane, and some visible parts of the middle ear.
Through the visualization of the ear canal and eardrum, the examiner can check for wax occlusion, foreign objects, and ear infections and inspect the eardrum for any problems.
Air conduction testing
Air conduction exams test the entire hearing system. Headphones are positioned on or over the ear (or earphones are inserted into the ear canal) so that test stimuli can be played into the individual being examined.
The sound wave travels from the outer ear canal, into the middle ear space, and reaches the inner ear organ (the cochlea), where the sound wave is converted into an electrical signal that the brain can compute.
Once the sound is presented, the patient is expected to respond—usually by pressing a button or raising their hand. In a diagnostic exam, the softest sound the patient can hear is determined by presenting a sequence of frequencies or tones at different intensity levels.
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, especially if the difference from octave sounds is significant.
Higher frequencies up to 10,000-20,000 Hz are also tested, especially when looking for damage from ototoxic drugs.
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 enables us to identify whether the hearing loss is in the outer, middle, or inner part of the ear. This involves placing a small vibrator, called a bone oscillator, on the bone behind the ear or the forehead.
The oscillator presents the sounds onto the bone, bypassing the outer and middle parts of the ear and going directly to the cochlea.
Bone conduction testing enables an audiologist to establish whether the identified hearing loss is conductive, sensorineural, or mixed.
Conductive hearing loss arises from issues in the outer or middle ear. Examples of conductive hearing loss are wax occlusion, hole or perforation of the eardrum, or a middle ear infection.
Sensorineural hearing loss is developed when there is damage to the hearing organ (cochlea) or the nerve to the brain, such as age-related hearing loss or noise-induced hearing loss. This usually involves no damage or blockage in the path of the sound coming through the air-conduction route.
Mixed hearing loss involves elements of both conductive and sensorineural hearing loss.
Speech testing
A comprehensive exam requires speech testing. In a speech test, the examiner checks how a patient hears speech and how they respond to it. Various speech tests exist. The Speech Reception Threshold (SRT) and Word recognition (WR) testing are the most common speech tests performed.
The examiner’s voice or recorded material can be used for a speech test. Recorded material is considered the gold standard because it allows for more controlled, consistent, and accurate testing.
SRT tests determine the softest level of speech an individual can hear and repeat the word back accurately. This test applies only to children and adults who can speak.
If the patient cannot repeat the words back, alternative tests can be performed. For example, Speech Detection Testing (SDT)—where the patient can give a signal by raising their hands or pressing a button when they hear the word, rather than repeating the word back.
Word recognition testing is used to see how well an individual can hear and comprehend speech at an easily audible level. A sentence or carrier phrase is used (“Say the word ______”) and the patient repeats the word.
So, for example: “Say the word hello,” and the patient would repeat the word hello. Sometimes, to check if a retrocochlear pathology is present, word recognition testing is conducted at a very loud level, for example, 90 dB.
Diagnostic audiometers
Before selecting the correct treatment, it is crucial to ensure a comprehensive diagnosis of the cause and type of hearing loss.
Amplivox has developed a set of innovative and user-friendly diagnostic audiometers that perform various hearing loss tests, including AC, BC, speech, and special tests: ABLB, Stenger, SISI, Tone decay, HLS, and MHA.
References and further reading
Centers for Disease Control Prevention (2018). Noise & Hearing Loss Prevention: Hearing Loss Prevention Programs. Accessed at: https://www.cdc.gov/niosh/programs/ppops/hlp.html
Centers for Disease Control Prevention (2022). Screening and Diagnosis of Hearing Loss. Accessed at: https://www.cdc.gov/ncbddd/hearingloss/screening.html
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