Noise-Induced (4 kHz Notch)
A sharp dip in hearing around 4 kHz, the frequency range most vulnerable to loud noise. Common after prolonged exposure to gunfire, heavy machinery, or loud music. The rest of the hearing range may be relatively intact, which is why people with this pattern often do not notice it at first.
Summary
- Severity
- Slight24 dB HL
- Most loss at
- 4 kHz · 65 dB
Degree of the worse ear, averaged over all eight frequencies, on the scale used by U.S. audiologists (ASHA)
Pure-tone average (PTA)
- Left ear
- 7dB
- Normal
- Right ear
- 7dB
- Normal
What’s a pure-tone average?
Pure-tone average is the quietest tone each ear can just hear, averaged across three pitches central to speech (500 Hz, 1 kHz, and 2 kHz). It’s the single number U.S. audiologists use to sum up an audiogram. 15 dB or lower is normal hearing, and every 10 dB higher means sounds need to be about twice as loud to be heard. Internationally, the World Health Organization averages four pitches, adding 4 kHz, so where high pitches have more loss its number comes out higher.
Thresholds by frequency
| Hz | L | R |
|---|---|---|
| 250 | 0 | 0 |
| 500 | 0 | 0 |
| 1k | 5 | 5 |
| 2k | 15 | 15 |
| 3k | 50 | 50 |
| 4k | 65 | 65 |
| 6k | 40 | 40 |
| 8k | 20 | 20 |