Year 9 Science · Unit 4 · Lesson 7
Challenge Worksheet
Learning Goals
Read the graph
The bar chart below shows the approximate hearing range (lowest to highest frequency) for five species. Study the graph, then answer the questions.
Data: Adapted from Heffner & Heffner (1998), Comparative hearing, Blackwell Handbook of Sensation and Perception
(a) Which species shown has the widest frequency range? Calculate how many Hz wide that range is.
(b) Bats evolved hearing up to 110,000 Hz — far beyond any other animal shown. Explain why this ultrasound hearing ability is a survival advantage for bats. Refer to echolocation in your answer.
(c) Calculate the wavelength of a bat echolocation pulse at 80,000 Hz in air. Use v = 343 m/s. Show your working. (Hint: λ = v ÷ f)
Design a mini-investigation
Scenario
You suspect that workers in a busy Sydney café experience dangerously loud noise levels during peak periods, potentially exceeding Safe Work Australia’s limit of 85 dB for 8 hours. You want to measure and evaluate the risk before recommending changes to the café owner.
Plan your investigation. Fill in each section below.
| Aim (what are you trying to find out?) | |
| Equipment needed | |
| How you would measure dB levels over a shift (describe your method in 3–4 steps) | |
| How you would compare your data to Safe Work Australia guidelines |
1. If you measured an average of 92 dB over a 6-hour peak period, what would you conclude about the risk to workers? Refer to specific Safe Work Australia time/dB limits.
2. Write three specific recommendations you would make to the café owner to reduce noise-induced hearing loss risk for staff. For each, explain the science behind why it would help.
Wrap Up
In one sentence, what was the main idea of this lesson?