In simple terms, tones at different frequencies are tested. When the patient hears a tone, they press a button, and this response is recorded. This establishes the “hearing threshold” for that specific frequency. A distinction is also made between bass tones (low frequencies) and treble tones, which are in the higher frequency range.

Frequencies are typically tested from 125 Hertz to 8000 Hertz. Hertz refers to the number of vibrations per second—so 125 Hertz means 125 vibrations per second, and 8000 Hertz means 8000 vibrations per second. These frequencies are displayed graphically on the X-axis (horizontally). The Y-axis (vertically) shows the sound level, measured in decibels (dB), at which the patient can hear the tone at each frequency. On the graph, the right ear is represented by red points or lines, and the left ear by blue points or lines. The test is conducted one ear at a time.

At 0 on the decibel scale, the sound corresponds to the faintest level a healthy ear can detect.

To ensure the most accurate results, the test is ideally conducted using high-attenuation headphones or inside a soundproof booth. This minimizes background noise, chatter, and sounds such as traffic. The instrument used for the measurement is called an audiometer.

In a complete pure-tone audiometry assessment, bone conduction testing is also performed. In this part of the test, sound is transmitted directly to the cochlea of the inner ear. If the air conduction and bone conduction curves overlap, the hearing loss is often sensorineural in origin. This means the impairment is located in the cochlea or higher up in the auditory pathway.

If, on the other hand, bone conduction thresholds are normal while air conduction thresholds are reduced, this suggests a conductive hearing loss. There are also mixed hearing losses, where both air and bone conduction deviate from normal values.

Sensorineural hearing loss is the most common type. This category includes noise-induced hearing loss, which often presents as greater impairment in the higher frequencies (treble tones) compared to the lower frequencies (bass tones). Age-related hearing loss (presbycusis) is also classified as sensorineural. Sensorineural hearing loss can be either congenital or acquired, with acquired forms being the most common.

Because age-related hearing loss is so prevalent, it is important to begin monitoring how hearing changes over time. Below is a video that addresses this topic.