Hardness of hearing or deafness is also classified based on the level of loss of hearing measured with the help of an audiogram, which measures the average loss of hearing across various sound frequencies. There are six levels of loss of hearing, varying from slight loss of hearing to complete deafness.

• Slight loss of hearing: 16 to 40 dB

The person has difficulty with hearing and/or understanding soft speech and whispering. Also understanding speech from a larger distance or when someone is speaking in a noisy environment gives trouble.

• Moderate loss of hearing: 41-55 dB

The person has difficulty hearing and/or understanding speech at a normal volume level. Understanding at a short distance is no longer easy and speech in a quiet environment gives trouble. A telephone call becomes troublesome.

• Serious loss of hearing: 56-70 dB

The person has trouble understanding loud speech and warning signals, such as sirens of police cars or ambulances, are not heard (well) either. A telephone talk gets really difficult.

• Very serious loss of hearing: 71-90 dB

Understanding speech is seriously troublesome. It is possible in some way, but lip reading is needed. The person also does no longer hear louder sounds in the surroundings, such as a sound of a drilling machine or the engine of a lorry. Talking by the telephone is no longer possible.

• Deafness: 90-120 dB

The sound of speech itself is not sufficient to understand anything. Most ambient noises are no longer heard.

• Total deafness: 120 dB and more

In this situation there is total deafness. Only very loud sounds (and vibrations) are perceived.

Source: Hoorzaken.nl