Year 9 Science · Unit 4 · Lesson 6

Sound Waves

Challenge Worksheet

Name

Date

Class

Learning Goals

Trace a cause-and-effect chain from an increase in sound frequency to the brain's perception of pitch.
Evaluate a claim about hearing damage at concerts using knowledge of the dB scale and gradual hair cell damage.
Propose engineering and personal protective equipment solutions to reduce hearing risk.

Warm Up

Because… chain

Fill in the missing effects. Each box on the right is the effect of the box on the left. The chain shows what happens when sound frequency increases (a higher-pitched note is played).

Sound frequency increases (higher-pitched note played)

→

Wavelength decreases (speed stays constant in air — v = fλ)

→

Compressions arrive at the ear more frequently

→

Hair cells in the cochlea tuned to that higher frequency are stimulated

→

Nerve signals travel from cochlea to auditory cortex in the brain

→

Overall outcome:

Go Deeper

Evaluate the claim

A concert venue claims…

"Our speakers are set at a safe volume because you can't hear any damage happening. If the sound were hurting your ears, you'd feel pain immediately. We keep levels below 100 dB, which is well under the 120 dB pain threshold, so there's nothing to worry about."

(a) Explain why hearing damage from loud noise can occur without immediate pain. In your answer, describe what happens to hair cells in the cochlea during prolonged exposure to sound above 85 dB, and why this damage often goes unnoticed at the time.

Challenge 3 marks

(b) The decibel (dB) scale is logarithmic, not linear. Explain what this means in practice. Specifically: (i) what does it mean that 100 dB is 10 times more intense than 90 dB rather than just 10% more? (ii) why is the safe workplace limit set at 85 dB — not 100 dB — even though the pain threshold is 120 dB?

Challenge 3 marks

(c) Propose two engineering controls (changes to the venue or equipment) and one item of personal protective equipment (PPE) that could reduce hearing damage risk at live music events. For each suggestion, briefly explain the scientific principle that makes it effective.

Challenge 3 marks

Wrap Up

In one sentence, what was the main idea of this lesson?