A study published in the Journal of the American Academy of Audiology found that only 43 per cent of patients could correctly identify the degree of their own hearing loss when shown their audiogram without explanation. The graph that results from a comprehensive hearing test contains precise clinical information, yet its layout, symbols, and terminology are unfamiliar to most people encountering it for the first time. Understanding how to read an audiogram gives you a clearer picture of your hearing health and a stronger foundation for discussing treatment options with your audiologist. This guide covers every component of the audiogram, from axis labels to clinical patterns, in plain language.
What Is an Audiogram
An audiogram is a graph that records the results of pure-tone audiometry, the core test in any hearing evaluation. During a hearing test, your audiologist plays tones at specific pitches and volumes through headphones or insert earphones. You indicate, usually by pressing a button, when you hear each tone. The softest level at which you can detect a tone at least 50 per cent of the time is called your hearing threshold. These thresholds are plotted on the audiogram, creating a visual map of your hearing sensitivity.
The audiogram displays results for each ear separately. Right ear results are traditionally marked in red and left ear results in blue. By plotting both ears on the same graph, the audiologist can immediately see whether your hearing is symmetrical or whether one ear has greater loss than the other. This distinction matters because asymmetric hearing loss can indicate different underlying causes and may require a different clinical approach.
Audiograms are produced in a sound-treated booth or quiet room to prevent background noise from masking the test tones. The equipment is calibrated to international standards so that thresholds are measured accurately in decibels of hearing level, abbreviated as dB HL. This calibration ensures that an audiogram taken at one clinic can be reliably compared with an audiogram taken at another.
Understanding Frequency on the X-Axis
The horizontal axis of an audiogram represents frequency, measured in hertz (Hz). Frequency corresponds to pitch. Low frequencies, such as 250 Hz, represent low-pitched sounds like a bass drum or the rumble of a truck. High frequencies, such as 8000 Hz, represent high-pitched sounds like birdsong, a ticking clock, or the consonant sounds in speech such as s, f, and th.
A standard audiogram tests frequencies from 250 Hz to 8000 Hz. These frequencies cover the range most critical for understanding speech and hearing environmental sounds. The frequencies tested are 250, 500, 1000, 2000, 4000, and 8000 Hz. Some audiologists also test 3000 Hz and 6000 Hz, particularly when evaluating hearing loss related to noise exposure, because these intermediate frequencies often show early signs of damage.
The layout of the x-axis is logarithmic rather than linear. This means the spacing between 250 Hz and 500 Hz is visually larger than the spacing between 4000 Hz and 8000 Hz, even though both pairs represent a doubling of frequency. The logarithmic scale reflects how human hearing perceives pitch. We hear changes in low frequencies as more distinct than equivalent changes in high frequencies, and the audiogram's axis mirrors that perception.
Speech understanding depends heavily on the range from 500 Hz to 4000 Hz. Vowel sounds carry most of their acoustic energy below 1000 Hz, while consonant sounds that give speech its clarity sit between 2000 Hz and 6000 Hz. A person with normal hearing through the low frequencies but reduced sensitivity above 2000 Hz will often report that they can hear people talking but cannot make out exactly what is being said. This pattern, which shows up clearly on an audiogram, is one of the most common reasons people seek a hearing evaluation.
Understanding Decibels on the Y-Axis
The vertical axis of an audiogram represents intensity, measured in decibels of hearing level (dB HL). Intensity corresponds to loudness. The axis starts at the top with negative values such as -10 dB HL, representing sounds quieter than average normal hearing, and extends downward to 120 dB HL, representing extremely loud sounds.
The orientation of the y-axis is the opposite of what many people expect. Thresholds plotted higher on the graph represent better hearing, because the person can detect softer sounds. Thresholds plotted lower on the graph represent poorer hearing, because louder sounds are needed before the person can detect them. An audiogram for someone with normal hearing shows symbols clustered near the top of the graph, close to the 0 dB HL line. An audiogram for someone with significant hearing loss shows symbols further down the graph.
The scale from -10 to 120 dB HL covers the full range of human hearing. Normal conversational speech sits around 60 dB HL. A whisper registers near 20 dB HL. A lawnmower produces sound near 90 dB HL. When your audiogram shows a threshold of 45 dB HL at 2000 Hz, it means the softest sound you can detect at that pitch needs to be as loud as a typical library conversation. Someone with normal hearing at that same frequency would detect a sound roughly 25 decibels quieter.
The decibel scale is logarithmic, which means that a 10-decibel increase represents a perceived doubling of loudness. A 20-decibel difference between two frequencies on your audiogram represents a fourfold difference in perceived volume. This is why even moderate shifts on the audiogram can have a noticeable effect on your ability to hear clearly in daily life.
Air Conduction vs Bone Conduction Testing
A complete audiogram typically includes two types of testing: air conduction and bone conduction. Comparing the results of both tests allows the audiologist to determine the type of hearing loss you have.
Air conduction testing delivers sound through headphones or insert earphones. The sound travels through the outer ear, across the eardrum, through the middle ear bones, and into the cochlea in the inner ear. Air conduction thresholds reflect the function of the entire hearing pathway from ear canal to auditory nerve. On the audiogram, air conduction results for the right ear are marked with a red circle (O) and for the left ear with a blue cross (X).
Bone conduction testing delivers sound through a vibrating pad placed on the mastoid bone behind the ear. The vibration bypasses the outer and middle ear entirely, stimulating the cochlea directly through the skull. Bone conduction thresholds reflect the function of the inner ear and neural pathways only. On the audiogram, bone conduction results are marked with specific bracket symbols. A right ear bone conduction threshold uses a red angle bracket pointing left, and a left ear bone conduction threshold uses a blue angle bracket pointing right.
The relationship between air conduction and bone conduction results is called the air-bone gap. When air conduction thresholds are poorer than bone conduction thresholds by 10 decibels or more at any frequency, an air-bone gap exists. This gap indicates a conductive component to the hearing loss, meaning sound is not travelling efficiently through the outer or middle ear. Causes include fluid behind the eardrum, a perforated eardrum, otosclerosis, or blockage from earwax.
When air conduction and bone conduction thresholds are approximately equal and both are below normal limits, the hearing loss is sensorineural. This means the inner ear or auditory nerve is not processing sound correctly. Sensorineural hearing loss accounts for roughly 90 per cent of all permanent hearing loss and is the type most commonly associated with ageing and noise exposure.
When both an air-bone gap and elevated bone conduction thresholds are present, the hearing loss is classified as mixed. This means there is damage or dysfunction in both the conductive pathway and the sensorineural pathway. Accurate audiogram interpretation depends on measuring both air and bone conduction at each frequency.
Degrees of Hearing Loss
The thresholds on your audiogram are used to classify the degree of hearing loss. The classification is based on the pure-tone average (PTA), which is the average of your thresholds at 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. However, audiologists also consider individual frequency thresholds, because a single frequency with significant loss can affect communication even when the overall average appears acceptable.
Normal Hearing (0 to 20 dB HL)
Thresholds between 0 and 20 dB HL across all frequencies are considered within the normal range. People with normal hearing can detect very soft sounds and typically have no difficulty understanding speech in quiet or moderately noisy environments. Occasional thresholds at 15 or 20 dB HL at individual frequencies are common and usually not clinically significant unless they represent a change from previous testing.
Mild Hearing Loss (21 to 40 dB HL)
Mild hearing loss means the softest sounds you can detect are between 21 and 40 dB HL. People with mild loss often hear conversation clearly in quiet settings but struggle when background noise is present or when the speaker is at a distance. Soft consonant sounds such as f, s, th, and sh may be missed. Many people with mild loss do not realise they have a hearing issue until they are tested, because they compensate unconsciously by lip-reading or asking for repetition.
Moderate Hearing Loss (41 to 55 dB HL)
Moderate hearing loss means thresholds fall between 41 and 55 dB HL. At this level, normal conversation at a typical volume of 60 dB HL is audible but may lack clarity, particularly in noisy environments. Group conversations, restaurant settings, and telephone calls become consistently difficult. People with moderate loss frequently need the television volume set higher than others prefer. Hearing aids are generally recommended at this degree of loss, because the gap between normal speech levels and hearing thresholds is large enough to benefit from amplification.
Moderately Severe Hearing Loss (56 to 70 dB HL)
Moderately severe hearing loss occupies the range between 56 and 70 dB HL. Conversational speech at normal volume is partially audible but insufficient for clear understanding. People at this level often miss a significant portion of what is said without visual cues or repetition. Even moderately loud environmental sounds may go unnoticed. Hearing aids with higher amplification, and sometimes assistive listening devices, are typically recommended.
Severe Hearing Loss (71 to 90 dB HL)
Severe hearing loss means thresholds between 71 and 90 dB HL. At this degree, only loud speech and loud environmental sounds are audible without amplification. Normal conversation is not heard at all. People with severe loss rely heavily on hearing aids and often use additional strategies such as speech-reading, captioning services, and alerting devices for doorbells and smoke alarms. Power hearing aids are required to provide sufficient amplification.
Profound Hearing Loss (91+ dB HL)
Profound hearing loss indicates thresholds above 91 dB HL. At this level, even very loud sounds may not be detected without amplification. Conventional hearing aids may provide limited benefit, and cochlear implants are often considered as an alternative or supplement. People with profound loss may detect vibrations from very loud sounds but cannot rely on hearing alone for speech understanding without significant intervention.
What Different Audiogram Patterns Mean
Beyond the overall degree of loss, the shape or configuration of the audiogram provides important diagnostic information. Three patterns appear most frequently in clinical practice.
Noise Notch
A noise notch is one of the most recognisable patterns on an audiogram. It appears as a distinct dip in hearing sensitivity, most often at 4000 Hz, with thresholds improving at higher frequencies such as 6000 Hz or 8000 Hz. The notch forms because the hair cells in the cochlea that respond to frequencies around 4000 Hz are particularly vulnerable to damage from loud sound. Occupational noise from machinery, recreational noise from firearms and concerts, and prolonged headphone use at high volumes can all produce this pattern.
In its early stages, a noise notch may affect only one ear or may be more pronounced in one ear than the other, depending on the source of exposure. Rifle shooters, for example, often show a more pronounced notch in the ear closest to the rifle stock. As exposure continues over years, the notch typically deepens and widens, eventually merging with the high-frequency slope of age-related loss. Detecting a noise notch early provides an opportunity to intervene with hearing protection before the damage progresses.
Flat Loss
A flat loss shows thresholds that are approximately equal across all tested frequencies. The audiogram line runs roughly horizontal, indicating that hearing sensitivity is reduced by a similar amount at low, mid, and high frequencies. Flat losses are often conductive in nature, caused by conditions affecting the middle ear such as otitis media with effusion (fluid behind the eardrum) or otosclerosis. When a flat sensorineural loss is present, it may indicate a genetic cause or result from certain medications that are toxic to the ear, such as some chemotherapy drugs or high-dose intravenous antibiotics.
People with a flat moderate loss often report that everything sounds equally quiet rather than selectively muffled. Speech sounds soft but not specifically unclear in the way that a high-frequency loss produces. This distinction in subjective experience matches what the audiogram shows. Because all frequencies are affected, the relative clarity of consonants versus vowels is preserved, but overall volume is reduced.
Sloping Loss
A sloping loss is the most common configuration among adults. The audiogram shows normal or near-normal thresholds in the low frequencies, with progressively poorer thresholds as frequency increases. The line on the audiogram slopes downward from left to right. This pattern is typical of age-related hearing loss, also called presbycusis, and reflects the progressive deterioration of hair cells at the basal end of the cochlea, which processes high frequencies.
The clinical impact of a sloping loss is distinctive. Low-frequency hearing allows a person to detect that someone is speaking and to hear the vowel sounds that carry vocal energy. High-frequency hearing provides the consonant sounds that give speech its clarity and distinctiveness. When high-frequency thresholds drop, a person hears that speech is happening but cannot resolve the details. Words like "cat," "hat," "sat," and "fat" become difficult to distinguish because the differentiating consonant sounds fall in the frequency range where hearing is weakest. This is why people with a sloping loss so often say "I can hear but I cannot understand" and why the problem is most noticeable in background noise, where the already-weak consonant cues are further masked.
Frequently Asked Questions
What do the symbols on an audiogram mean?
The most common symbols on an audiogram are a red circle and a blue cross. The red circle represents the right ear measured by air conduction, and the blue cross represents the left ear measured by air conduction. Bone conduction results use a red triangle bracket for the right ear and a blue triangle bracket for the left ear. Some audiologists also use a red square for right ear masked air conduction and a blue square for left ear masked air conduction. A legend on the audiogram typically identifies each symbol used.
What is a normal reading on an audiogram?
A normal audiogram reading shows thresholds between 0 and 20 decibels HL across all tested frequencies from 250 Hz to 8000 Hz for both ears. This means the softest sounds you can detect at each pitch fall within the range considered typical for healthy hearing. Thresholds between 20 and 25 decibels HL are sometimes classified as borderline normal. Anything above 25 decibels HL at any frequency indicates some degree of hearing loss at that pitch.
Can I read my audiogram without professional help?
You can identify basic patterns on your audiogram, such as which frequencies show elevated thresholds and whether one ear is more affected than the other. Understanding the general shape and degree of hearing loss provides useful context. However, accurate audiogram interpretation requires clinical training. An audiologist considers your audiogram alongside speech testing results, tympanometry, your medical history, and your reported listening difficulties before making recommendations. Reading your own results gives you a starting point for discussion, not a substitute for professional advice.
What does a noise notch on an audiogram look like?
A noise notch on an audiogram appears as a distinct dip in hearing sensitivity, most often at 4000 Hz, with thresholds improving again at 6000 Hz and 8000 Hz. On the graph, the plotted line drops downward around the 4000 Hz mark, forming a notch shape. This pattern is characteristic of noise-induced hearing loss and reflects damage to the hair cells in the cochlea that respond to high-frequency sounds. In early stages, the notch may be visible only at 4000 Hz. With continued noise exposure, the notch often widens to include 3000 Hz and 6000 Hz.
Works Cited
American Speech-Language-Hearing Association. "Type, Degree, and Configuration of Hearing Loss." ASHA, 2024, asha.org.
Clark, James G. "Uses and Abuses of Hearing Loss Classification." American Speech-Language-Hearing Association, vol. 23, no. 7, 1981, pp. 493-500.
Katz, Jack, et al. Handbook of Clinical Audiology. 7th ed., Wolters Kluwer, 2020.
Margolis, Robert H., and Richard H. Wilson. "Audiogram Interpretation: A Manual for Students and Clinicians." Journal of the American Academy of Audiology, vol. 30, no. 5, 2019, pp. 414-427.
National Acoustic Laboratories. "Understanding Your Audiogram: A Guide for Consumers." NAL, Australian Government, 2023, nal.gov.au.
World Health Organization. "World Report on Hearing." WHO, 2021, who.int/publications/i/item/world-report-on-hearing.