What is a common beginning indicator of noise-induced hearing loss (NIHL)?

What is a common beginning indicator of noise-induced hearing loss (NIHL)?

• A. A notch at 4-6 kHz with a 15 dB HL deficit above thresholds at 1-2 kHz
• B. A notch at 3-6 kHz that is 10 dB HL higher than the poorest threshold at 500-1000 Hz
• C. Notch at 3-6 kHz that is 15 dB HL higher than the poorest threshold at 500-1000 Hz
• D. A notch at 2-4 kHz that is 15 dB HL higher than the poorest threshold at 500-1000 Hz

Answer: (C)

A high-frequency notch on an audiogram is the classic early sign of noise-induced hearing loss. Damage from loud noise typically first shows up in the 3–6 kHz range, often strongest around 4 kHz, while lower frequencies stay relatively preserved. When this high-frequency dip is at least about 15 dB worse than the poorest threshold at lower frequencies (commonly compared to the 500–1000 Hz region), it creates a pattern that clinicians recognize as a noisy notch. This option matches that pattern exactly: a notch in the 3–6 kHz region with a 15 dB HL difference compared to the poorest threshold at 500–1000 Hz, which is the standard criterion for an NIHL notch. Other choices are less consistent because they either use too small a difference (10 dB), focus on a slightly different frequency range (2–4 or 4–6 kHz only, or reference 1–2 kHz), or do not frame the comparison to the typical low-frequency baseline (500–1000 Hz) that defines the notch’s significance.

A high-frequency notch on an audiogram is the classic early sign of noise-induced hearing loss. Damage from loud noise typically first shows up in the 3–6 kHz range, often strongest around 4 kHz, while lower frequencies stay relatively preserved. When this high-frequency dip is at least about 15 dB worse than the poorest threshold at lower frequencies (commonly compared to the 500–1000 Hz region), it creates a pattern that clinicians recognize as a noisy notch.

This option matches that pattern exactly: a notch in the 3–6 kHz region with a 15 dB HL difference compared to the poorest threshold at 500–1000 Hz, which is the standard criterion for an NIHL notch. Other choices are less consistent because they either use too small a difference (10 dB), focus on a slightly different frequency range (2–4 or 4–6 kHz only, or reference 1–2 kHz), or do not frame the comparison to the typical low-frequency baseline (500–1000 Hz) that defines the notch’s significance.