Pure-tone average (PTA): the single number from your audiogram

What the pure-tone average is

The pure-tone average (PTA) is a single number derived from a standard audiogram by averaging the hearing thresholds at three specific frequencies: 500 Hz, 1000 Hz, and 2000 Hz. These frequencies were chosen because they span the core of the speech frequency range, where most of the acoustic energy in conversational speech is concentrated.

PTA is reported in decibels hearing level (dB HL). A PTA of 0 dB HL would mean the ear responds at the average threshold of young, healthy adults. In practice, thresholds in this range mean hearing is very sensitive; higher numbers mean softer sounds cannot be detected.

How it is calculated

The calculation is straightforward. Add the threshold values at 500 Hz, 1000 Hz, and 2000 Hz, then divide by three.

For example, if an audiogram shows thresholds of 20 dB HL at 500 Hz, 25 dB HL at 1000 Hz, and 30 dB HL at 2000 Hz, the PTA is (20 + 25 + 30) divided by 3, which equals 25 dB HL.

Some audiologists use a four-frequency PTA that also includes 4000 Hz, which is particularly relevant when noise-induced hearing loss or high-frequency audiometric patterns are a concern. When both PTAs are reported, they can give different impressions of hearing status, and it is worth asking which version was used.

Classification ranges

Different organizations use slightly different cutoff values, but the most widely cited classification in clinical practice divides PTA ranges roughly as follows:

A PTA of 25 dB HL or better is typically classified as normal limits for adults. The World Health Organization uses 20 dB HL as its normal cutoff, which means the WHO categories are slightly stricter. For children, many clinicians apply a 15 dB HL normal criterion because even mild losses can affect speech and language development.

PTAs from roughly 26 to 40 dB HL are described as mild hearing loss. Communication in quiet environments is often manageable, but noise and distance increase difficulty. The 41 to 55 dB HL range is moderate loss; conversational speech at normal volumes becomes difficult without assistance. Moderate-to-severe spans 56 to 70 dB HL, with severe at 71 to 90 dB HL. A PTA above 90 dB HL is classified as profound, indicating that only very loud sounds produce any auditory response.

These ranges are classification labels, not prescriptions. An audiologist interprets the full audiogram, not just the PTA, when evaluating someone’s functional hearing and communication needs.

Where the PTA comes from and why

The choice of 500, 1000, and 2000 Hz reflects the acoustic properties of speech. Vowel sounds carry much of their energy in this range, and intelligibility for everyday conversation depends substantially on these frequencies. By averaging thresholds here, PTA gives a single metric that correlates reasonably well with how well someone understands speech in quiet conditions.

PTA also has practical applications beyond individual clinical decisions. It is used in epidemiological research to compare hearing status across populations and age groups. NIOSH surveillance data on occupational hearing loss frequently reports PTA as the primary outcome measure. Legal and compensation frameworks for noise-induced hearing loss, including workers compensation systems in many countries, use PTA as the basis for quantifying hearing impairment.

The limitations of PTA

PTA’s main limitation is that it was not designed to capture high-frequency hearing loss well. The frequencies most vulnerable to noise damage, typically 3000 Hz, 4000 Hz, and 6000 Hz, are not included in the standard three-frequency calculation. A person with a classic noise-induced notch at 4000 Hz, where thresholds drop sharply before recovering at 8000 Hz, may have a PTA that falls in the normal range even though they have measurable cochlear damage and may be noticing difficulty in noisy environments.

For this reason, NIOSH occupational hearing loss surveillance standards look at the standard threshold shift (STS), which uses the average of 2000, 3000, and 4000 Hz, a different frequency grouping that is more sensitive to early noise-induced damage.

PTA also gives no information about speech understanding or word recognition. Two people with identical PTAs may have very different word recognition scores in quiet, different speech-in-noise performance, and different functional communication needs. The audiogram provides context that a single number cannot.

PTA in context

The PTA is a useful summary tool, not a complete picture of hearing function. Reading it alongside the full audiometric threshold curve, word recognition scores, tympanometry results, and the patient’s reported communication difficulties gives a much richer clinical picture.

If the PTA seems inconsistent with someone’s reported difficulty, that inconsistency is clinically meaningful and worth investigating further, not explaining away.

If symptoms persist or change, see an audiologist or physician.