An audiogram is a graph that provides a visual representation of a person's hearing sensitivity across different frequencies (from low-pitched to high-pitched sounds). The horizontal axis represents frequency (expressed in Hertz), while the vertical axis represents loudness (or sound intensity, expressed in decibels). The audiogram is used to show the softest sound a person is able to hear at each frequency.
How Is the Audiogram Test Performed?
The audiogram test is carried out in a soundproof booth, where a device called an audiometer delivers sounds at different levels and frequencies. The person being tested gives a signal (by raising a hand or pressing a button) each time a sound is heard, allowing the audiologist to record hearing sensitivity at every frequency. These results are then plotted on the audiogram.
What Does an Audiogram Tell Us?
An audiogram provides clear information about:
- Hearing Sensitivity at Different Frequencies: It helps determine which sound frequencies are difficult to hear. For example, some people hear low-pitched sounds (bass) far better than high-pitched sounds (soprano).
- The Degree of Hearing Loss: The audiogram classifies the degree of hearing loss, which may range from normal hearing to severe or profound hearing loss, depending on how loud a sound must be at each frequency.
- The Type of Hearing Loss: The audiogram helps identify the type of hearing loss – whether it is conductive hearing loss (caused by problems in the outer or middle ear), sensorineural hearing loss (caused by problems in the inner ear) or mixed hearing loss (a combination of both).
How Is an Audiogram Read?
- The Horizontal Axis (Frequencies)
Frequencies range from low (250 Hz, roughly the sound of a large vehicle) to high (8000 Hz, roughly the sound of a bird). Low frequencies appear on the left side of the graph, while high frequencies appear on the right. - The Vertical Axis (Intensity)
Intensity or loudness is expressed in decibels (dB), starting at 0 dB (the softest sound healthy ears should be able to hear) and increasing to higher levels that indicate a greater degree of hearing loss. Higher decibel levels are placed lower down on the audiogram and represent different degrees of hearing loss. - The Symbols on the Audiogram
Specific symbols are used for each ear on the audiogram (X for the left ear and O for the right ear). When an audiogram shows different values for each ear, this indicates asymmetric hearing loss, meaning that one ear may be more affected than the other.
Why Is the Audiogram Important?
Early Diagnosis of Hearing Problems:
The audiogram is a key tool for detecting hearing problems early, which is critical in preventing further deterioration of hearing. In children, the audiogram is essential, as early hearing loss can affect their language and social development.
Treatment Planning:
The results of the audiogram allow the audiologist to determine the type of treatment required, which may include hearing aids, other assistive devices or surgical intervention.
Monitoring Changes in Hearing:
An audiogram can be used to monitor changes in a person's hearing over time. This is particularly important for those exposed to loud noise or living with health conditions that affect hearing.
Use in Hearing Aid Fitting:
The audiogram also serves as a guide for fitting hearing aids, ensuring that they are adjusted to amplify precisely the frequencies an individual most needs to hear.
Classification of Hearing Loss on an Audiogram
- Normal Hearing (0-25 dB): The person has healthy hearing without any difficulty.
- Mild Hearing Loss (26-40 dB): The person may have difficulty hearing soft sounds or hearing in the presence of background noise.
- Moderate Hearing Loss (41-55 dB): Sounds usually need to be amplified, and normal conversation can be difficult to follow.
- Moderately Severe Hearing Loss (56-70 dB): Everyday environmental sounds may be unclear or hard to hear.
- Severe Hearing Loss (71-90 dB): Even loud sounds are difficult to hear without assistive devices, and ordinary conversation becomes very challenging.
- Profound Hearing Loss (91+ dB): High levels of amplification are required, and the individual usually relies on hearing aids or other techniques in order to understand conversation.