Reasons Not to Describe Degree of Hearing Loss As Percentage
The Common Misconception About Hearing Loss
We often hear people say they have lost a certain percentage of their hearing, or that they are, for instance, sixty per cent deaf in their left ear. In this article we explain why using percentage to describe the degree of hearing loss is almost always incorrect, and we share a better way to describe the degree of hearing loss.
Where the Concept of Hearing Loss Percentage Comes From
Hearing loss percentage is a concept used to quantify the level of disability from hearing loss. It is an estimate of earning capacity as a percentage of what someone might be earning without a hearing loss. A 68% hearing loss corresponds to an average loss in income of 68%. This is the correct way to think about hearing loss percentage.
This concept is based on averages, and incomes will vary across the population of hard of hearing individuals.
The percentage is based on hearing thresholds, which cannot fully capture one’s ability to understand speech and communicate. Therefore, in practice, some discretion goes into determining hearing disability.
Why There Is a Common Misconception About Hearing Loss Percentage
Audiologists summarise hearing test results on an audiogram, which is often simplified to cover the range from zero to one hundred decibels.
Each value on an audiogram is a hearing threshold and is a different concept from the level of disability.
To see the dangers of confusing these concepts, notice that the decibel scale is logarithmic. For example, a sound at 36 decibels has twice the sound pressure of a sound at 30 decibels. The percentage scale, however, is linear.
During a hearing test, the audiologist measures your hearing thresholds, which should not be confused with a statistic used to quantify the level of disability caused by hearing loss.
The More Precise Way To Describe Hearing Loss Severity
Hearing loss severity can be described using the categories mild, moderate, severe or profound hearing loss or normal hearing. A sloping audiogram may be described better as “mild hearing loss at low frequencies and a moderate hearing loss at higher frequencies in both ears.”
The key is to remember that the values measured during a hearing test are in terms of decibels, and can for example be described as “50-decibel hearing loss at 1,000 hertz in the left ear.”
How to Calculate Hearing Loss Percentage
In 1979, the American Academy of Otolaryngology published a formula for calculating hearing loss percentage, which to date remains in use in many states in the United States.
In case you still want to calculate hearing loss percentage, then the steps to using the formula are as follows:
Step 1: Calculating Average Loss In Each Air Based On An Audiogram
You will need an audiogram with both air-conduction and bone-conduction thresholds, with hearing thresholds at 500Hz, 1000Hz, 2000Hz and 3000Hz. These frequencies are the most important to understanding human speech. The threshold values from both ears are needed.
Hearing thresholds can change over time, so if you do not already have an audiogram obtained within the past three months, you should first book a hearing consultation.
Before calculating percentage hearing loss, negative values are set to zero, and values above one hundred are adjusted to 100.
Your data might look like this:
Frequency |
Left Ear |
Right Ear |
500 Hz |
60 |
55 |
1,000 Hz |
60 |
65 |
2,000 Hz |
75 |
70 |
3,000 Hz |
60 |
70 |
Refer to our guide on how to read an audiogram in case you are unsure about how to obtain the values.
Add up the values from each column, divide by four and round to the nearest whole number to obtain the average:
Left ear:
Right ear:
260 / 4 = 65
With the values above, we can say there is 64 dB average hearing loss in the left ear and 65 dB average hearing loss in the right ear.
Step 2: Calculating the Level of Impairment in Each Ear
The level of impairment in each ear as a percentage increases by 1.5% for every decibel hearing loss above 25 dB. Hearing loss at or below 25 dB is considered to not impact one’s income.
Using the same set of values from the previous step, we get:
Left ear:
64 - 25 = 39
39 x 1.5 = 58.5
Right ear:
65 - 25 = 40
40 x 1.5 = 60
The results are interpreted as 58.5% and 60% impairment in the left and right ears, respectively.
Step 3: Determining the Overall Hearing Loss Percentage
A five to one weighting is applied to the better and worse ears, respectively.
The reason is that remaining hearing ability in the better ear will allow people to hear relatively well, even if one ear has a large degree of impairment.
Continuing from the above example, the overall hearing loss percentage is calculated as follows:
Better ear (left ear):
Worse ear (right ear):
60 x 1 = 60
Combined:
292.5 + 60 = 352.5
352.5 / 6 = 58.75
The interpretation of this final value is that the overall hearing impairment is 58.75%. This value might be used, along with some discretion, to calculate compensation for a hearing-impairment.
Shortcomings of the Hearing Loss Percentage Formula
The hearing loss percentage formula has several shortcomings.
- It is one single statistic that aims to summarise the overall hearing health situation of one individual. A lot of valuable information is lost in the process of calculating this value.
- Since hearing loss percentage is an average value, it does not tell us whether the hearing loss is flat (with similar thresholds across all frequencies), sloped, dented, or has a different shape.
- The formula disregards any hearing loss at or below 25 dB, while in reality, it is possible to see greatly reduced speech understanding even at relatively low thresholds.
- The inputs to the formula are pure-tone thresholds at four specific frequencies across a range from 500 Hz to 3,000 Hz.
- Pure-tone thresholds do not necessarily translate into our ability to understand speech or distinguish different sounds.
Examples of How the Hearing Loss Percentage Formula Fails
The hearing loss percentage formula is not rigorous, and there are cases where it fails to yield sensible results.
One example is when someone has rather high hearing thresholds, like in the following table:
Frequency |
Left Ear |
Right Ear |
500 Hz |
90 |
90 |
1,000 Hz |
95 |
95 |
2,000 Hz |
95 |
95 |
3,000 Hz |
90 |
95 |
Using the same three steps to calculate the overall hearing loss percentage, we arrive at 102.25% impairment. This is above 100% and does not make sense!
Another example of where the formula falls short is when someone has a relatively good hearing at most frequencies, but a high threshold at one or two frequencies:
Frequency |
Left Ear |
Right Ear |
500 Hz |
5 |
5 |
1,000 Hz |
95 |
95 |
2,000 Hz |
0 |
0 |
3,000 Hz |
0 |
0 |
Someone with a 95 dB threshold at 1,000 Hz would face difficulties in their daily life.
However, plugging the values into the hearing loss percentage formula would tell us that this person has no hearing-impairment.
Try the hearing loss simulator to understand how people with hearing loss hear the world.
Summary
When you do a hearing test, the audiologist measures your hearing thresholds in terms of decibels. They should not be confused with hearing loss percentage, which quantifies the level of disability caused by hearing loss.
The appropriate ways to describe hearing loss severity are by categories (for example mild, moderate, severe or profound hearing loss) or to keep the threshold values at each frequency in each ear.
If you still want to calculate hearing loss percentage, you can follow the three steps in this article, but you should be aware of the shortcomings of the hearing loss percentage formula.
About Incus
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