3.10.2.3
Hearing defects and hearing aids
Medical Physics | AQA A-Level Physics
- Age-related hearing loss: affects all frequencies but is worst at high frequencies. The equal loudness curves shift upward, meaning louder sounds are needed for the same perceived loudness. This is a gradual, irreversible process.
- Noise-induced hearing loss: caused by prolonged exposure to excessive noise. It produces a characteristic dip in sensitivity around 4000 Hz on an audiogram. Unlike ageing, the affected frequency range is more specific.
- An audiogramA graph used in clinical hearing tests that plots hearing level (in dB) against frequency. A normal audiogram is a flat line near 0 dB. Deviations downward from this line indicate hearing loss at those frequencies. is a graph of hearing level against frequency used to diagnose hearing defects. Normal hearing gives a roughly flat line near 0 dB. Hearing loss shows as dips below the baseline at affected frequencies.
- The key part is that you can distinguish between the two causes on an audiogram: ageing gives a gradual slope worsening at high frequencies, while noise damage gives a sharp dip centred around 4 kHz.