Diagnosis and Testing
Decibel (dB) is a logarithmic unit used to measure sound level
A person who is not able to hear as well as someone with normal hearing, 25 dB in better ear (able to hear whispers) in both ears – is said to have hearing loss.
Mild hearing loss: Hear 26-40 dB in better ear (hear and repeat words spoken in normal voice at 1 meter).
Moderate hearing loss: Hear 41-60 dB in better ear (hear and repeat words spoken in raised voice at 1 meter).
Severe hearing loss: Hear 61-80 dB in better ear (hear some words when shouted into better ear).
Profound hearing loss: Hear 81 dB in better ear (unable to hear and understand even shouted voice).
Presbycusis: Gradual loss of hearing with age; 30-35% at age 65 and older and 40-50% at age 75 and older. The loss is usually greater for high-pitched sounds while able to hear low-pitched sound clearly.
Hyperacusis: Extreme sensitivity to everyday sounds.
Diplacusis: Hearing same notes at different pitches.
'Deaf' people mostly have profound hearing loss, which implies very little or no hearing.
Routine hearing tests are important:
For monitoring and early identification of potential worsening of hearing loss.
For developing strategy for treatment and prevention of further hearing loss.
For identifying noise hazards in your lifestyle.
Different diagnostic procedures and tests available:
Pure-tone audiometry is the most common hearing test. It defines the faintest tones a person can hear at selected pitches, or frequencies and to determine the type and degree of hearing loss. However, ability to hear and comprehend complex sounds requires more specific testing.
Speech audiometry tests your ability to hear and understand human speech. One test determines your speech reception threshold. The second test assesses speech discrimination. Additional speech testing may be required for complex situations such as understanding speech in background noise.
Auditory Brainstem Response (ABR) by electrodes to analyze brain activity to assess the functionality of the auditory neural pathway. The auditory steady state response, or ASSR test, objectively identifies the brain’s responses to different pitches and volumes.
Otoacoustic Emissions Test (OAE test) measures hair cell function in the inner ear and differentiate between the sensory and neural components of sensorineural hearing loss.
Tests for the middle ear including tympanometry, acoustic reflex measures, and static acoustic measures. Tympanometry detects fluid in the middle ear, eardrum perforation, and blockage in the ear canal. Acoustic reflex testing is used to determine if the ear’s natural and involuntary reflex to lower the volume of very loud sounds is working properly. Static acoustic impedance measures the physical volume of air in the ear canal to identify problems with the eardrum or ventilation tubes.