From the Guidelines
To interpret an audiogram, one must analyze the graph showing a person's hearing thresholds at different frequencies, considering the symbols for each ear, frequency range, and hearing level in decibels, as well as patterns of hearing loss and air-bone gaps, as outlined in the clinical practice guidelines for hearing loss 1. When interpreting an audiogram, it's essential to understand the components of the graph. The horizontal axis represents frequency in Hertz (Hz), ranging from low (125-250 Hz) to high (4000-8000 Hz), while the vertical axis shows hearing level in decibels (dB) with normal hearing at 0-25 dB. The symbols on the chart, usually circles or red for the right ear and X's or blue for the left ear, indicate the hearing thresholds for each ear.
Key Points to Consider:
- Normal hearing ranges from -10 to 25 dB, with varying degrees of hearing loss categorized as mild (26-40 dB), moderate (41-55 dB), moderately severe (56-70 dB), severe (71-90 dB), and profound (greater than 90 dB) 1.
- The pattern of hearing loss across frequencies can suggest different causes, such as sloping loss indicating age-related or noise-induced hearing loss, and flat loss suggesting conductive hearing loss 1.
- Air-bone gaps, where bone conduction thresholds are better than air conduction, indicate conductive hearing loss.
- Speech recognition scores, often included alongside the audiogram, provide insight into functional hearing ability beyond pure tone thresholds, measured as the percentage of words a person can correctly identify at comfortable listening levels 1.
Clinical Practice Guidelines:
The clinical practice guideline for age-related hearing loss 1 emphasizes the importance of comprehensive diagnostic evaluation, including pure tone thresholds, speech audiometry, tympanometry, and acoustic reflex testing. Pure tone average (PTA) is considered the gold standard for detecting hearing loss, establishing the pattern and degree of hearing loss, and informing diagnosis and treatment.
Limitations and Considerations:
While PTA is a reliable and low-cost diagnostic tool, limitations include workforce shortages, particularly in lower-income areas, and challenges in testing older adults with cognitive dysfunction 1. Testing variations and standard diagnostic test-retest variability can also influence results. In clinical practice, interpreting an audiogram requires careful consideration of these factors to accurately diagnose and manage hearing loss, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life 1.
From the Research
Interpreting an Audiogram
To interpret an audiogram, it is essential to understand the different components and how they relate to hearing loss.
- An audiogram typically displays frequency on the Y-axis and hearing level on the X-axis 2.
- The hearing level is measured in decibels (dB) and the frequency is measured in Hertz (Hz).
- A standard audiogram requires specialized equipment and personnel, but smartphone-based hearing tests can also be used as an aid in the initial evaluation of hearing loss 3.
Key Components of an Audiogram
- The audiogram edge frequency is the frequency at which the hearing loss begins, and it has been found to be related to tinnitus pitch 4.
- The degree of hearing loss is typically categorized as normal, mild, moderate, severe, or profound.
- Audiograms can be used to estimate hearing thresholds and to guide the fitting of hearing aids, although some research suggests that fitting the pure tone audiogram may not always be the best approach 5.
Methods for Estimating Audiograms
- Bayesian active learning methods can be used to estimate audiograms quickly and accurately, providing an estimate of threshold as a continuous function of frequency 6.
- These methods can be used to determine the frequency and levels of stimuli for the next trial, allowing for accurate audiogram estimates in less than 50 trials or 4 minutes.
- Smartphone-based hearing tests, such as the uHear application, can also be used to estimate hearing thresholds and to guide the decision to initiate treatment for hearing loss 3.