Hearing impairment is a partial or total inability to hear. It is a disability which is sub-divided in two categories of deaf and hard of hearing.
- “Deaf” means persons having 70 dB hearing loss in speech frequencies in both ears.
- “Hard of hearing” means person having 60 dB to 70 dB hearing loss in speech frequencies in both ears.
A pure tone audiometry test measures the softest, or least audible, sound that a person can hear. During the test, you will wear earphones and hear a range of sounds directed to one ear at a time. The loudness of sound is measured in decibels (dB).
Assessment of Hearing Impairment
Measurement of Air Conduction Thresholds (ACT)
- ACT is to be measured using standard Pure Tone Audiometry by an Audiologist for Right Ear and Left Ear separately
- In case of non-reliable ACT, additional tests are recommended such as Immittance, and Speech audiometry or Auditory Brainstem Response (ABR) Testing
- Measuring ACT may be difficult in children aged 3-5 years. In such cases, Conditioned Pure Tone audiometry/Visual Reinforcement Audiometry (VRA) shall be conducted. ABR or Auditory Steady State Response (ASSR) testing can be advised for the estimation of ACT in infant and young children
Computation of Percentage of Hearing Disability
- Calculate Pure tone average of ACT for 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz for Right Ear and Left ear separately (whenever there is no response at any frequency ACT is to be considered as 95dB)
- Monaural percentage of hearing disability is to be calculated as per the ready reckoner given below separately for Right Ear and Left Ear
|Monaural PTA in dB||% of Disability|
|0 to 25||0|
Formula for Calculating Percentage of Hearing Disability
Percentage of Hearing Disability = (Better ear % of hearing disability x 5) + (Poorer ear % of hearing disability) / 6
WHO Hearing Impairment Grading
|Grade of impairment*||Corresponding audiometric ISO value**||Performance||Recommendations|
|* Grades 2, 3 and 4 are classified as disabling hearing impairment (for children, it starts at 31 dB)|
** The audiometric ISO values are averages of values at 500, 1000, 2000, 4000 Hz.
|0 – No impairment||25 dB or better|
|No or very slight hearing problems. Able to hear whispers.|
|1 – Slight impairment||26-40 dB|
|Able to hear and repeat words spoken in normal voice at 1 meter.||Counseling. Hearing aids may be needed.|
|2 – Moderate impairment||41-60 dB|
|Able to hear and repeat words spoken in raised voice at 1 meter.||Hearing aids usually recommended.|
|3 – Severe impairment||61-80 dB|
|Able to hear some words when shouted into better ear.||Hearing aids needed. If no hearing aids available, lip-reading and signing should be taught.|
|4 – Profound impairment including deafness||81 dB or above|
|Unable to hear and understand even a shouted voice.||Hearing aids may help understanding words. Additional rehabilitation needed. Lip-reading and sometimes signing essential.|
Hearing Impairment is recognized as a disability under RPWD Act 2016 in India. People with benchmark hearing disability can claim benefits provided under various government schemes. You should visit a government hospital to get disability certificate for hearing impairment.