PTA (Pure Tone Audiometry) Test
Pure Tone Audiometry (PTA) is a standard hearing test used to evaluate an individual's hearing sensitivity. It measures the softest or least audible sound that a person can hear at various frequencies (pitches). The test is crucial in diagnosing hearing loss and helps in determining the degree and type of hearing loss.
How PTA Works
Testing Environment:
- PTA is conducted in a soundproof booth to eliminate external noise, ensuring accurate results.
Equipment:
- The test uses an audiometer, a device that generates pure tones at various frequencies and intensities.
- The patient wears headphones or insert earphones to listen to these tones.
Procedure:
- The audiologist presents pure tones at different frequencies (typically ranging from 250 Hz to 8,000 Hz) and varying intensities (measured in decibels, dB).
- The patient is asked to indicate (usually by pressing a button) when they hear a tone, even if it is very faint.
Testing Each Ear Separately:
- Each ear is tested individually to determine if there is a difference in hearing sensitivity between the two ears.
Bone Conduction Test:
- In addition to air conduction (through headphones), bone conduction testing may be done using a small vibrator placed behind the ear on the mastoid bone. This bypasses the outer and middle ear, testing the inner ear directly.
Results Interpretation
Audiogram:
- The results of a PTA test are plotted on an audiogram, a graph that shows the hearing threshold levels across different frequencies.
- The vertical axis represents the hearing threshold level in decibels (dB), and the horizontal axis represents the frequency in Hertz (Hz).
- A lower threshold level (closer to 0 dB) indicates better hearing at that frequency.
Types of Hearing Loss:
- Normal Hearing: Hearing thresholds between 0-20 dB.
- Mild Hearing Loss: Thresholds between 21-40 dB.
- Moderate Hearing Loss: Thresholds between 41-55 dB.
- Moderately Severe Hearing Loss: Thresholds between 56-70 dB.
- Severe Hearing Loss: Thresholds between 71-90 dB.
- Profound Hearing Loss: Thresholds above 90 dB.
Hearing Loss Patterns:
- Conductive Hearing Loss: Poor air conduction but normal bone conduction.
- Sensorineural Hearing Loss: Both air and bone conduction thresholds are elevated.
- Mixed Hearing Loss: A combination of conductive and sensorineural hearing loss.
Importance of PTA
- Diagnosis: PTA helps audiologists diagnose the type and degree of hearing loss.
- Treatment Planning: The results guide the selection and programming of hearing aids or other treatments.
- Monitoring: It can be used to monitor hearing changes over time, especially in cases of progressive hearing loss or when exposed to ototoxic medications or environments.
PTA is a fundamental tool in audiology, providing detailed information about a person’s hearing health.