An audiogram visually represents an individual’s hearing ability, mapping how well they perceive sounds across different pitches and volumes. Hearing tests, which produce audiograms, are routinely conducted to diagnose and monitor hearing loss. These tests are foundational for understanding one’s hearing health, capturing the quietest sounds a person can hear.
Understanding Your Audiogram
An audiogram is a graph with two axes illustrating hearing thresholds. The horizontal X-axis represents sound frequency (Hertz or Hz), indicating pitch from low (bass) to high (treble). Audiograms typically test frequencies from 250 Hz to 8000 Hz, encompassing most speech sounds. The vertical Y-axis denotes sound intensity or loudness (decibels Hearing Level or dB HL), with softer sounds at the top and louder sounds towards the bottom.
During a hearing test, an audiometer delivers pure tones at specific frequencies and intensities; the patient signals when they hear a sound. The softest sound a person can hear for a given frequency is their hearing threshold. These thresholds are plotted on the audiogram using specific symbols: a red circle (‘O’) marks the right ear, and a blue ‘X’ marks the left ear for air conduction testing. Bone conduction results, which measure how sound travels directly to the inner ear, are represented by symbols like ‘<' or '[' for the right ear and '>‘ or ‘]’ for the left ear.
What is Pure Tone Average (PTA)?
Pure Tone Average (PTA) is a numerical summary that condenses audiogram data into a single value for each ear. It represents the average of an individual’s hearing threshold levels at frequencies most relevant to understanding speech. This average provides a snapshot of overall hearing sensitivity. Clinicians use PTA as a convenient, standardized reference to assess the general degree of hearing loss and compare hearing abilities between ears or over time.
PTA is a reliable tool for detecting hearing loss and is foundational in clinical diagnostics. It quantifies hearing impairment, particularly for speech understanding in quiet environments. While it simplifies the audiogram, its utility lies in providing a concise and consistent measure for initial assessment.
Calculating Your Pure Tone Average
To calculate the standard three-frequency Pure Tone Average (PTA), focus on hearing thresholds obtained at 500 Hz, 1000 Hz, and 2000 Hz for each ear. First, locate these frequencies on the X-axis of your audiogram. Then, for each frequency, identify the corresponding symbol for the ear (e.g., ‘O’ for the right ear, ‘X’ for the left ear) and read across to the Y-axis to determine its decibel Hearing Level (dB HL) threshold.
Once you have the three threshold values for one ear, sum these decibel values. For example, if thresholds are 30 dB at 500 Hz, 40 dB at 1000 Hz, and 50 dB at 2000 Hz, the sum is 120 dB. Divide this total by three to obtain the Pure Tone Average for that ear (e.g., 120 / 3 = 40 dB). This calculation provides a single average threshold representing hearing sensitivity in crucial speech frequencies.
While the three-frequency PTA is widely used, other variations exist depending on the purpose. Some calculations might include a fourth frequency, such as 4000 Hz, for a four-frequency PTA, which can provide a more comprehensive view, especially for high-frequency hearing. For specific applications like industrial hearing conservation, or to better estimate speech understanding in noise, other frequency combinations or weighted averages might be used. However, the 500 Hz, 1000 Hz, and 2000 Hz average remains a common and practical calculation for general assessment.
Interpreting Your PTA Results
The Pure Tone Average (PTA) indicates the overall degree of hearing loss in an ear. A PTA of 25 dB HL or less is generally considered to be within the normal hearing range. Hearing loss is classified based on decibel ranges: a PTA between 26 and 40 dB HL indicates mild hearing loss, while 41 to 55 dB HL signifies moderate hearing loss.
A PTA from 56 to 70 dB HL suggests moderately severe hearing loss, and 71 to 90 dB HL points to severe hearing loss. A PTA greater than 90 dB HL is categorized as profound hearing loss. These classifications help understand the impact of hearing loss on daily communication.
PTA is a simplified measure and does not capture the full picture of an individual’s hearing abilities. Factors such as speech understanding in noisy environments, the configuration of hearing loss across all frequencies, or the personal impact on daily life are not directly reflected in the PTA. While PTA offers a valuable initial assessment, consulting a hearing healthcare professional is recommended for a comprehensive interpretation of your audiogram and personalized advice regarding your hearing health.