Degree of hearing loss.

Degree of Hearing Loss
Fig 1: Degree of Hearing Loss
Degree of hearing impairment refers to the severity of the loss. The following numbers in the table are representative of the patient’s hearing loss range in decibels (dB HL), which are commonly used classification.

Mild hearing loss: Soft noises cannot be heard. Understanding of speech is difficult in a loud environment.

Moderate hearing loss: Soft and moderately loud noises cannot be heard. It becomes difficult to follow speech in noisy situations

Severe hearing loss: Conversations have to be conducted loudly. Group conversations are possible only with a lot of effort.

Profound hearing loss: Some very loud noises cannot be heard. Even with intense effort and without hearing aid, communication is no longer possible

Audiogram / Speech Banana
Fig 2: Audiogram / Speech Banana
Audiogram is the main tool to assess the type and degree of hearing loss of a patient. It contains the hearing thresholds for multiple frequencies in comparison to a normal, healthy ear. The thresholds are normally assessed at 125, 250, 500, 1000, 2000, 3000, 4000 and 8000 Hz. They are measured in dB HL (hearing loss) where 0 dB HL refers to the threshold of a healthy ear. The grey shaded area indicates the frequencies and sound levels that correspond to speech. It is also called “speech banana” due to its characteristic shape

Audiogram for a person with normal hearing:

Audiogram for a person with age-related hearing loss:

Configuration of Hearing Loss

Audiogram / Speech Banana for age related hearing loss
Fig 3: Age related hearing loss Audiogram
The configuration (or shape) of the hearing loss attribute to the degree and pattern of hearing loss across frequencies (tones) which are illustrated in a graph called an audiogram. As an example, a high-frequency loss is a hearing loss that only affects the high tones. Its configuration in the low tones would show good hearing and in high tones would show poor hearing. Similarly if only the low frequencies were affected, the configuration would show degree of hearing loss for low tones and superior hearing for high tones. The flat configurations indicate the same amount of hearing loss for high and low tones.

Bilateral versus Unilateral Hearing Loss

Bilateral hearing loss account for hearing loss in both ears. Unilateral hearing loss (UHL) accounts for hearing loss in one ear and the hearing is normal in other ear. The extent of hearing loss can be from mild to very severe to profound. UHL can occur at any age in both adults and children. Approximately 1 in 10,000 children is born with UHL, and nearly 3-4% of school-age children have UHL. Children with UHL are much prone to risk for having academic, speech-language, and social-emotional difficulties than normal hearing children. This is because the children do not receive appropriate intervention since the UHL is often not identified

Below are some possible causes of UHL:

  • Syndromes such as Down and Usher syndrome
  • Head injury
  • Hearing loss that runs in the family (genetic orhereditary)
  • An outer, middle, or inner ear abnormality
  • Illnesses or infections such as CMV, Rubella
  • Exposure to loud noise
  • Traumatic brain injury (TBI)

Symmetrical versus asymmetrical

When the degree and configuration of hearing loss are same in both the ears it accounts for symmetrical hearing loss. And when the degree and configuration are different in each ear it means asymmetrical hearing loss.

Fluctuating versus stable hearing loss

Fluctuating means hearing loss that alters over time, sometimes gives the better feeling, sometimes getting worse. On the other hand, stable hearing loss remains the same and does not change over time.

Progressive versus sudden hearing loss

When hearing loss continues to becomes worse over time it is progressive hearing loss. Hearing loss which occurs quickly mean sudden hearint loss. Sudden hearing loss requires urgent medical attention to determine its cause and treatment.