Echo & Sound Reflection Simulation
This interactive simulation shows how sound waves travel from a source, strike a reflective surface, and return as an echo. Pupils can switch between four illustrated environments — a cliff face, a city building, a canyon, and an underwater SONAR scene — each rendered with atmospheric depth. Pressing ▶ Send Sound fires animated circular wavefronts that expand outward from the source toward the reflector, then return as the echo at lower amplitude. A live distance label tracks how far the sound has travelled at any point in the animation.
The distance slider (5–340 m) and temperature slider (−20 to +40 °C) update all metrics in real time: echo delay, speed of sound (v = 331 + 0.6T), and total path length. Below 17 m the simulation correctly flags that no distinct echo is perceived, because the human ear cannot separate two sounds less than 0.1 s apart. The SONAR scene shows the same physics applied underwater, connecting the concept to real-world technology.
Class Activity — How Far Away Is the Cliff?
Year 8/9 · ~50 min · Pairs
Objective: Use the echo formula to calculate distance; investigate how temperature affects the speed of sound.
Hook (5 min) Open the simulation on Cliff Face at 100 m. Fire the sound without showing the distance slider. Ask: “The echo took 0.58 seconds to return. How far away is the cliff?” Take estimates, then reveal the formula.
Direct Instruction (5 min) Write up: d = v × t ÷ 2. Explain why we halve — the sound travels to the wall and back, so the total path is 2d. Walk through one worked example using the values on screen.
Pair Investigation (18 min) Pupils move the distance slider to five different positions and complete the table using the metrics bar — they do not read the distance display, only the echo delay, and calculate d themselves.
| Echo delay (s) | Calculated d (m) | Simulation d (m) | Match? |
|---|---|---|---|
Then switch to Canyon and repeat for two values. Ask: “Does it matter which scene you use? Why not?”
Temperature Investigation (10 min) Keep distance fixed at 100 m. Move the temperature slider from −20 °C to +40 °C and record how the echo delay and speed change. Ask:
- Why does the echo return faster on a hot day?
- A thunderstorm happens in winter (−5 °C) and summer (30 °C). Which would give a longer delay between lightning and thunder for the same distance?
SONAR extension (5 min) Switch to SONAR. Ask: “Sound travels at 1480 m/s in water, not 343 m/s. If a submarine detects an echo after 0.4 s, how deep is the seabed?” Pupils calculate by hand: d = 1480 × 0.4 ÷ 2 = 296 m.
Exit Ticket (5 min)
- A sound echo returns after 0.6 s at 20 °C. How far away is the reflector?
- Why can you not hear a distinct echo from a wall 5 m away?
- Name two real-world uses of the echo principle.
Adaptation: Foundation pupils are given the formula pre-written and use only the Cliff scene with three set distances. Higher pupils investigate the effect of temperature on minimum echo distance (d_min = v × 0.1 ÷ 2) and explain why this changes with temperature.