What an Audiogram Shows
This is not medical advice. An audiogram is interpreted by an audiologist. This explains what the chart is so that the conversation is easier.
In workplace investigations, hearing-risk evidence should stay separate from productivity or attendance data; further details addresses the work-pattern side rather than medical or acoustic assessment.
What is plotted
Frequency across the horizontal axis, low on the left to high on the right, typically 250 Hz to 8 kHz.
Hearing level down the vertical axis, in dB HL, with better hearing at the top. The scale runs downward — a point lower on the chart is a worse threshold, which is the opposite of most graphs and the commonest reading error.
For additional technical context, see NIDCD on noise-induced hearing loss.
Two symbols per frequency, one per ear, conventionally distinguished by shape and colour.
What dB HL means
Not sound pressure.
dB HL is referenced to normal hearing at each frequency — 0 dB HL is the average threshold of a healthy young adult for that tone, not a physical constant.
Which means the scale is already normalised for the ear's varying sensitivity, and a flat line across the chart represents normal hearing rather than equal sound pressure.
It is a third decibel quantity, distinct from dB SPL and dBFS, and mixing them is easy.
Reading the shape
A flat line near the top: thresholds within normal limits.
A gradual downward slope toward the high frequencies: the pattern commonly associated with age.
A dip at 4–6 kHz with recovery above it: the pattern associated with noise exposure.
Both together is usual in anybody older who has been exposed, and separating them is the audiologist's job rather than the chart's.
Why one test tells you little
A single audiogram is a snapshot with no baseline.
Thresholds vary between individuals, and a result within normal limits does not establish that nothing has been lost — only that what remains is within the range.
The finding is the change. A shift across a series over years is what a conservation programme exists to detect, and it is invisible in any single chart.
So the value is in keeping them, and in having a baseline taken before significant exposure where that is still possible.
What it does not measure
Speech in noise. The commonest functional complaint, and a threshold test does not assess it.
Tinnitus, which is a perception rather than a threshold.
And the effort of listening, which is what people actually experience and has no line on the chart.
Normal thresholds and real difficulty coexist, and being told the chart is fine is not the same as being told nothing is wrong.
The short version
- Frequency runs left to right and hearing level runs downward, so a lower point is a worse threshold — the commonest reading error
- dB HL is referenced to normal hearing at each frequency rather than to sound pressure, so a flat line means normal
- A gradual high-frequency slope suggests age; a dip at 4–6 kHz with recovery above suggests noise
- A single audiogram has no baseline, and the finding is the change across a series over years
- It does not measure speech in noise, tinnitus, or listening effort
- Normal thresholds and genuine difficulty coexist, so a chart described as fine is not a statement that nothing is wrong