When does hearing loss become a disability or restriction?
Tone threshold audiometry measures hearing performance at individual pitches. Speech audiometry provides information on how well the person concerned can still communicate. But from what percentage of hearing loss should we take action?
ENT specialists or hearing aid acousticians measure the hearing ability of their patients in order to determine the need for a hearing aid, to recommend a suitable hearing aid or hearing implant or to assess the effectiveness of a hearing aid. Each ear is measured separately using headphones or bone conduction headphones, and in the case of free field audiometry, both ears are measured together using loudspeakers.
How does the hearing test work?
The hearing test is always compared with young adults with normal hearing! Tone audiometry measures how many decibels (dB) louder a particular sound has to be for the test person to hear it than people with normal hearing. In the case of hearing loss for number words, the volume at which just half of the numbers are correctly understood is measured - the test person's result is compared again with that of people with normal hearing. The so-called discrimination loss in speech audiometry with monosyllabic words shows the percentage (%) of words not understood or misunderstood at a certain volume.
Percent is a linear ratio: 100 percent is the whole, 50 percent is half, 25 percent is a quarter of the whole. Decibel, on the other hand, describes a logarithmic ratio: 6 decibels is twice as loud, 12 decibels is four times as loud, 0 decibels is equally loud, -6 decibels would be half as loud.
What percentage signifies more than a minor hearing loss?
If a hearing loss is described as a general percentage without any further description, this is a value that is used to determine the degree of disability and any reduction in earning capacity. It is determined according to standardized tables from speech or sound audiometry.
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What do the percentages mean for hearing loss?
| Hearing loss | Hearing loss (%) |
|---|---|
| Minor, mild hearing loss | 20-40 % hearing loss |
| Moderate hearing loss | 40-60 % hearing loss |
| profound hearing loss | 60-80 % hearing loss |
| Residual hearing | 80-90 % hearing loss |
| Deafness | 100% hearing loss |
This calculation, which is provided for Germany, has been implemented in many audiometers used to measure hearing ability and can be read out directly. This may be one of the reasons why this small numerical value is often used as a rough estimate of hearing ability. A decision regarding hearing assistance devices must always be based on a combination of sound and speech audiogram!
What the World Health Organization (WHO) says
The classification according to the World Health Organization (WHO) is becoming increasingly important. This is based on the average hearing loss for sounds with frequencies of 500 hertz, as well as 1, 2 and 4 kilohertz in the ear with better hearing, expressed in decibels. These dB figures are not directly comparable with the percentages, even if the gradation appears similar at first glance:
| Hearing loss | Hearing loss (dB) |
|---|---|
| Minor hearing loss | 20-40 dB hearing loss |
| Moderate hearing loss | 41-60 dB hearing loss |
| profound hearing loss | 61-80 dB hearing loss |
| Residual hearing, bordering on deafness | more than 80 dB hearing loss |
When does hearing loss affect everyday life?
The WHO defines "disabling hearing loss" as a hearing threshold of 35 dB or more in the better-hearing ear - and calls for those affected to have the option of hearing aids, among other things. In science and in everyday clinical practice, however, it is now generally recognized that unilateral hearing loss also restricts everyday life.
