Year 9 Science · Unit 4 · Lesson 7
Apply Worksheet
Learning Goals
Compare two
Complete the table to compare noise-induced hearing loss (NIHL) and age-related hearing loss (presbycusis).
| Feature | Noise-induced hearing loss (NIHL) | Age-related hearing loss (presbycusis) |
|---|---|---|
| Main cause | ||
| Typical age of onset | ||
| Frequency range affected first | ||
| Reversible? | ||
| Prevention method |
Real-world context
A 28-year-old sound engineer in Sydney has been working live music events without ear protection for 5 years, averaging about 6 hours per week at approximately 105 dB. A recent hearing test reveals reduced sensitivity at 4000 Hz, while lower frequencies remain normal. Safe Work Australia sets a noise limit of 85 dB for an 8-hour working day, with the allowable exposure time halving for every 3 dB increase above that limit.
(a) Which part of the cochlea is most likely damaged, and why? In your answer, refer to the location of high-frequency hair cells along the basilar membrane.
(b) Why is 4000 Hz commonly the first frequency to be affected in noise-induced hearing loss, even though the engineer is exposed to a wide range of frequencies at concerts?
(c) What Safe Work Australia guidelines should the engineer have followed? State the specific dB and time limits that apply to 105 dB, and suggest two practical protective measures.
Wrap Up
In one sentence, what was the main idea of this lesson?