Hearing care professionals use audiograms to figure out your level and type of hearing loss. Learn about audiogram types, symbols and tests.
When you get a hearing test, a hearing care professional plots your results on a graph that shows the softest sounds you can hear at different frequencies. This is called an audiogram. An audiogram is a complete mapping of your hearing ability in both ears. Your audiogram shows how soft a sound can get before you cannot hear it. Normal hearing is when you can hear sounds that are 20dB or less at all frequencies.
When you have hearing loss, your hearing range changes. There are two factors involved in how we hear sound:
- Frequencies – Frequencies are like the notes on a piano. Lower frequencies are the bass sounds, and higher frequencies are the soprano sounds.
- Decibels (dB) – Decibels measure loudness. 0-20 dB is very soft. 110dB is very loud and can be uncomfortable to hear.
For most people, hearing loss will begin by affecting the high frequencies of the human hearing range. Certain speech, environmental sounds, and music are challenging to hear for most people with hearing loss.
Audiogram symbols explained
One of the most significant issues with hearing loss is that it hinders your ability to understand speech. Speech sounds fall in various places on the audiogram, with most falling within the so-called “speech banana” (see image).
Audiogram symbols include:
- A red line showing the level of hearing of a person’s right ear
- A blue line showing the level of hearing in a person’s left ear
- Levels above the audiogram lines in the audiogram cannot be heard
- The X shows hearing in the left ear
- The O shows hearing in the right ear
Types of hearing loss
An audiogram can also show your type of hearing loss. There are three types of hearing loss.
- Sensorineural hearing loss means the origin of your hearing loss is in the inner ear, the cochlea, where the auditory sensory organ is. This hearing loss commonly comes from ageing. Other causes include hereditary conditions or trauma from explosions or long exposure to loud sounds. Hearing aids are beneficial for people with sensorineural hearing loss.
- Conductive hearing loss means the sound is not reaching your inner ear. This is often caused by a middle ear condition – like something blocking the middle ear.
- Mixed hearing loss is a combination of sensorineural and conductive hearing loss.
Here is an audiogram with typical sounds and the speech banana. It shows sensorineural hearing loss in the left ear. The person with this audiogram cannot typically hear the sounds in the white area.
The human hearing range
There are various sounds in our environment, ranging from faint sounds, like birdsong and rustling leaves to louder sounds like music, yelling, and industrial noise. We refer to the range that people with normal hearing can hear as the audible range.
Loudness and pitch
The human hearing range depends on a sound’s pitch – high or low – and a sound’s loudness. Pitch is measured in Hertz (Hz), and loudness is measured in decibels (dB).
The human hearing range starts at about 20 Hz for a person with normal hearing. That is about the same as the lowest pedal on a pipe organ. When it comes to loudness, sounds that are more than 85dB can be dangerous for your hearing in the case of prolonged exposure.