If you have experienced an audiometric test, chances are you have seen and been told the results of your test via a graph. But did you really understand the information? Was the information not communicated well to you? This article will provide, in general terms, an explanation of what an audiogram represents.
The audiogram is a chart of hearing sensitivity with frequency charted on the X- axis and intensity on the Y-axis. Intensity is the level of sound power measured in decibels; loudness is the perceptual correlate of intensity. Below is an example of an audiogram:
Most common way to measure hearing sensitivity is to measure pure-tone (sinusoid) thresholds.
Below is an example of an audiogram. The red line is the right ear of this particular worker. This audiogram represents Pure Tone Average (PTA). The average thresholds at 500, 1000, 2000 Hz are the frequencies most important for speech understanding . In this particular scenario, the PTA of the left ear was 93 dB compared to 50 dB of the right ear.
The magnitude of hearing loss is defined as follows:
- Normal hearing loss: 0 -15 dB. Some interpretations have normal hearing loss ranging up to 25 dB
- Slight hearing loss: 16-25 dB
- Mild hearing loss: 26-40 dB
- Moderate hearing loss: 41-55 dB
- Moderately-Severe hearing loss: 56-70 dB
- Severe hearing loss: 71-90 dB
- Profound hearing loss: 91+dB
There are 3 types of Hearing Loss to understand when reviewing your audiogram:
- Conductive is abnormality of the outer or middle ear. Usually temporary and medically treatable.The Impaired Ear (Conductive Loss) occurs when there is a disruption of the transmission of sound (Ex: fluid in the middle ear). Typically, this loss occurs in the outer or middle ear and many times is a temporary loss that can be treated medically.
- Sensorineural is damage to the inner ear or nerves of hearing. Usually permanent. The Impaired Ear (Sensorineural Loss) occurs for many reasons. Starting from age 20, the hair cells slowly begin to deteriorate. Hair cells can also be damaged from loud noises, medicine, head trauma or other causes. This type of hearing loss are mostly due to natural loss of hair cells.
- Mixed include both Conductive and Sensorineural.
Besides just understanding the audiogram, it is important to remember that audiometry is a subjective test requiring a verbal or physical response and therefore can be subjective. Audiometry tests all parts of the ear, the entire auditory system. The most common type of audiometry, that you and I are familiar with is the Pure Tone audiometry test. This type of test includes headphone, insert earphone or speaker. A machine called an audiometer is used to produce sounds at various volumes and frequencies (pitches).You listen to the sounds through headphones and respond when you hear them by pressing a button.This test evaluates the sensitivity of the entire hearing organ. The audiologist presents single frequency (“pure”) tones produced by a calibrated audiometer. The softest sounds heard by the subject at each pitch are recorded as the thresholds and are compared to normative values. This recorded comparison is found on the audiogram, a graph that you now understand what it means and how it benefits you by knowing what type, if any hearing loss you may have. The type of hearing loss you have is important because it determines what help or treatment is most suitable for you.