Hearing is a critical sense that can be damaged or diminished over time. There are two types of hearing loss that an audiogram can diagnose and monitor. Conductive hearing loss is experienced when sounds cannot be conducted through the structures of the inner ear. Sensorineural hearing loss occurs due to damage or injury to the structures of the inner ear or the nerve pathways that go between the ear and the brain. There are different hearing tests that can be done to determine the type and severity of hearing loss. An audiogram uses frequency and intensity to determine hearing health. Here is some more information about hearing loss, its causes, and how audiograms can be used to design a treatment plan for aural deterioration:
What Causes Conductive Hearing Loss?
Conductive hearing loss or CHL occurs when air conduction cannot occur through the entire outer ear anatomy. This includes the external ear canal, auricle, middle ear, and tympanic membrane. CHL can also be caused by a lack of bone conduction, which is the vibration of sound that is transmitted to the inner ear through the skull. Conductive hearing loss can be corrected through surgical interventions.
What Causes Sensorineural Hearing Loss?
Sensorineural hearing loss also referred to as SNHL is the most common type of permanent hearing loss, typically caused by chronic exposure to noise. Unlike conductive hearing loss, SNHL doesn’t respond to surgical intervention.
What is Chronic Noise Exposure?
Chronic noise exposure which damages the body’s ability to hear is defined as experiencing sounds of 85 dB (decibels) for prolonged periods of time. An easy way to determine if you are in this threshold of sound is by noticing how often you need to raise your voice to be heard. Normal conversation is typically in the 60dB range, so speaking louder than normal signals an environment of at least 80dB.
How Does an Audiogram Work?
An audiogram plots hearing test results on a chart. It displays how well frequency (low-pitched vs. high-pitched sounds) is heard, and how intensity (loudness, or volume) is heard. An audiogram will show results for each ear and determines the softest sound that can be heard at a variety of frequencies.
Frequency, also referred to as pitch, is a metric measured in Hertz (Hz). The vertical lines on an audiogram represent 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, and 8000Hz. Intensity is measured in decibels (dB). The softest sounds are at the top of the chart, and the loudest are at the bottom. The softest sound is 0dB, and the loudest is 120dB.
The y-axis on the audiogram represents the hearing threshold, and the x-axis represents frequency. Each ear is also separately represented, typically with an “O” for the right ear and an “X” for the left. In order to determine whether CHL or SNHL is the issue, bone conduction is also plotted on the chart.
The results of the audiogram will determine a variety of hearing health benchmarks including your threshold - the lowest sound that you can hear at least 50% of the time. It will also identify your speech reception threshold (SRT), acoustic reflex, and tympanometry.
For many, hearing loss can impact their ability to safely perform their jobs. The occupational medicine team at Lane Regional Medical Center is here to help with audiogram testing.
