Hearing: Normal hearing, Hearing Loss & Degree of hearing loss

Author: Dr. Ng. T. N. Minh

Post date:

What is normal hearing?

What is hearing loss?

How Are Sounds Measured?

Degrees of Hearing Loss

Etiology or cause of hearing loss


If you often find yourself in situations where it is difficul for you to keep up with conversations, especially in noisy environments.
Or, sometime you feel that the surrounding sound is muffle and the music event on max volume to is not enough for you.
What doctor said that you have hearing loss, there is problem with your hearing ability.
But sometime we dont understant what is considered hearing loss and what is considered a person with normal hearing ability?

What is normal hearing?

Normal hearing is the ability to hear sounds within the frequency range of 20 to 20,000 hertz. This means that a person with normal hearing can detect sounds that are as low as 20 hertz (a very deep bass) or as high as 20,000 hertz (a very high-pitched whistle). However, this range may vary depending on the individual’s age, health, and environmental factors. For example, some young people can hear sounds up to 28,000 hertz under ideal laboratory conditions1, but most adults lose some of their high-frequency hearing as they get older.

What is hearing loss?

Hearing loss is when you have trouble hearing sounds that other normal people can hear.
Hearing loss can be understood as the ability to hear sound is reduced in one or both ears.

How Are Sounds Measured?

Sounds can be measured in both Hertz (Hz) and decibels (dB).
Sound is a type of energy that travels in waves through the air or other materials. We can measure sound in different ways, depending on what we want to know about it. Here are some common ways to measure sound:
Sound intensity:
This is how loud or soft a sound is. We use a device called a sound meter to measure the sound pressure level (SPL) of a sound wave. The SPL is measured in units called decibels (dB). The higher the dB, the louder the sound. For example, a whisper is about 20 dB, while a jet engine is about 140 dB.

Sound frequency
This is how high or low a sound is. We use a device called a microphone to capture the sound wave and convert it into an electrical signal. Then we use a device called a spectrum analyzer to measure the frequency of the signal. The frequency is measured in units called hertz (Hz). The higher the Hz, the higher the pitch. For example, a human voice has a frequency range of about 300 to 3,000 Hz, while a dog whistle has a frequency of about 20,000 Hz
Decibels measure how loud a sound is. The following list of the average decibel ratings of familiar sounds was put together by the National Institute on Deafness and Other Communication Disorders (NIDCD)

Breathing: 10 dB.
Normal conversation: 60-70 dB.
Movie theater: 74-104 dB.
Motorcycles: 80-110 dB.
Sporting event at Levi’s Stadium: 94-110 dB.
Sirens: 110-129 dB.
Fireworks: 140-160 dB.
Any sound that is 85 dB or louder can cause permanent damage to the delicate hair cells within the inner ear over time.

Degrees of Hearing Loss

You go to the audiologist for a hearing test. You may be told that you have a mild hearing loss. This description is referred to as “the degree of hearing loss.” It is based on how loud sounds need to be for you to hear them.
Decibels, or dB, describe loudness. The term dB HL describes your hearing loss in decibels.
The table below shows a common way to classify hearing loss.

Degree of hearing loss 

Hearing loss range (dB HL)


–10 to 15


16 to 25


26 to 40


41 to 55

Moderately severe

56 to 70


71 to 90



Source: Clark, J. G. (1981). Uses and abuses of hearing loss classification. Asha, 23, 493–500. 

If you can only hear sounds when they are at 30 dB, you have a mild hearing loss. You have a moderate hearing loss if sounds are closer to 50 dB before you hear them.

'Hard of hearing' refers to people with hearing loss ranging from mild to severe. People who are hard of hearing usually communicate through spoken language and can benefit from hearing aids, cochlear implants, and other assistive devices as well as captioning.

'Deaf' people mostly have profound hearing loss, which implies very little or no hearing. They often use sign language for communication.

Causes of hearing loss and deafness

Although these factors can be encountered at different periods across the life span, individuals are most susceptible to their effects during critical periods in life.

Prenatal period

  • genetic factors including hereditary and non-hereditary hearing loss
  • intrauterine infections – such as rubella and cytomegalovirus infection.

Perinatal period

  • birth asphyxia (a lack of oxygen at the time of birth
  • hyperbilirubinemia (severe jaundice in the neonatal period)
  • low-birth weight 
  • other perinatal morbidities and their management.

Childhood and adolescence 

  • chronic ear infections (chronic suppurative otitis media)
  • collection of fluid in the ear (chronic nonsuppurative otitis media)
  • meningitis and other infections.

Adulthood and older age 

  • chronic diseases
  • smoking
  • otosclerosis
  • age-related sensorineural degeneration
  • sudden sensorineural hearing loss.

Factors across the life span 

  • cerumen impaction (impacted ear wax) 
  • trauma to the ear or head
  • loud noise/loud sounds
  • ototoxic medicines
  • work related ototoxic chemicals
  • nutritional deficiencies 
  • viral infections and other ear conditions
  • delayed onset or progressive genetic hearing loss.
If you think you may have hearing loss, it is important to see a doctor or hearing specialist for diagnosis and treatment. There are many different treatments available for hearing loss, including hearing aids, cochlear implants, and assistive listening devices.

The sooner hearing loss is treated, the better the chances of improving hearing and preventing further damage. If you have any concerns about your hearing, please see a doctor or hearing specialist right away.

Read more about:
Type of hearing loss
Thank you.