A normal level of Pure-Tone Average (PTA) is generally considered to be between 0-25 dB HL (decibels Hearing Level). This range indicates that an individual has normal hearing sensitivity across the frequencies crucial for understanding speech.
Understanding Pure-Tone Average (PTA)
The Pure-Tone Average (PTA) is a calculation used in audiology to estimate an individual's overall hearing sensitivity. It's specifically the average of the hearing thresholds at 500 Hz, 1000 Hz, and 2000 Hz. These frequencies are particularly important because they fall within the range of frequencies most critical for understanding spoken language.
How PTA is Calculated:
- Threshold Measurement: An audiologist measures the softest sound (threshold) a person can hear at each of the key frequencies (500 Hz, 1000 Hz, and 2000 Hz). These are measured in decibels Hearing Level (dB HL).
- Averaging: The thresholds (in dB HL) at 500 Hz, 1000 Hz, and 2000 Hz are added together.
- Divide by Three: The sum is then divided by three to calculate the average.
Relationship to Speech Understanding:
The PTA should closely approximate the Speech Reception Threshold (SRT), which is the softest level at which a person can correctly repeat spondaic words (two-syllable words with equal stress, like "baseball" or "hotdog"). The PTA and SRT should be within 5 dB of each other. It should also closely approximate the Speech Detection Threshold (SDT) within 6-8 dB. This close relationship validates the audiometric testing.
PTA Ranges and Hearing Loss:
Here's a general guideline for interpreting PTA values and associating them with levels of hearing loss:
| PTA Range (dB HL) | Hearing Loss Category |
|---|---|
| 0 - 25 | Normal Hearing |
| 26 - 40 | Mild Hearing Loss |
| 41 - 55 | Moderate Hearing Loss |
| 56 - 70 | Moderately Severe Hearing Loss |
| 71 - 90 | Severe Hearing Loss |
| 91+ | Profound Hearing Loss |
Important Considerations:
- Individual Variation: Hearing ability can vary significantly from person to person.
- Frequency Specificity: PTA provides an overview, but doesn't tell the whole story as hearing thresholds at other frequencies may also be affected. A complete audiogram gives a more detailed picture.
- Professional Evaluation: PTA is a tool used by audiologists and other hearing healthcare professionals as part of a comprehensive hearing evaluation. If you have concerns about your hearing, it's vital to consult with a qualified professional for proper diagnosis and management.
