Definition of hearing loss
Hearing loss can be classified or defined in many ways and categories. This definition / classification is used by the Global Burden of Disease studies, which is used by the WHO.
Mild hearing loss
What is mild hearing loss? On average, the most quiet sounds that people can hear with their better ear are between 25 and 34 dB. People who suffer from mild hearing loss will normally have some difficulties keeping up with conversations, especially in noisy surroundings.
Moderate hearing loss
What is moderate hearing loss? On average, the most quiet sounds heard by people with their better ear are between 35 and 49 dB. People who suffer from moderate hearing loss have problems hearing in many situations and will have difficulties keeping up with conversations. People with a moderate hearing loss will benefit from using hearing aids.
Moderately severe hearing loss
What is a moderately severe hearing loss? On average, the most quiet sounds heard by people with their better ear are between 50 and 64 dB. People who suffer from a moderately severe hearing loss have problems hearing in most situations when not using hearing aids.
Severe hearing loss
What is severe hearing loss? On average, the most quiet sounds heard by people with their better ear are between 65 and 79 dB. People who suffer from a severe hearing loss are very hard of hearing and will normally have to use powerful hearing aids. Often they also rely on lip-reading even when they are using hearing aids.
Profound hearing loss
What is profound hearing loss? On average, the most quiet sounds heard by people with their better ear are 80 dB or more. People who suffer from profound hearing loss have a very weak sense of hearing and need very strong hearing aids or implants, many also rely on lip-reading and/or sign language.
All these categories are normally defined using a measured audiometric average of 500, 1000, 2000 and 4000 Hz.
Disabling hearing loss
Global Burden of Disease (GBD) also defines a “disabling hearing loss”. A disabling hearing loss according to GBD is 35 dB or greater in the better ear in adults.
Unilateral hearing loss or bilateral hearing loss - or mixed
You can have a hearing loss in just one ear (unilateral hearing loss) or in both ears (bilateral hearing loss) as well as you can have a mixed hearing loss.
About Global Burden of Disease
The Global Burden of Disease Study (GBD) is a comprehensive regional and global research program of disease burden that assesses mortality and disability from major diseases.
Read more about the Global Burden of Disease Study here: http://www.healthdata.org/gbd or here: https://www.who.int/healthinfo/global_burden_disease/about/en/