Human Hearing Range Simulation
This interactive simulation lets pupils generate and hear pure sine wave tones across the full frequency spectrum, from infrasound through the audible range to ultrasound. A logarithmic frequency slider spans 20 Hz to 20 kHz — matching how human pitch perception actually works — with ten preset buttons hitting key reference points including the two boundary frequencies, concert A (440 Hz), and the region of peak human sensitivity (4 kHz).
A spectrum ruler displays the entire audible range as a colour-gradient bar with a live position marker. When a tone is playing, the waveform panel shows a real oscilloscope trace from the audio buffer. The metrics bar updates live with frequency, period T, wavelength in air (using v = 343 m/s), and the zone classification. Below 20 Hz or above 20 kHz the display flags the tone as outside human hearing. All explanations — infrasound, ultrasound, the decibel scale, Snell’s law — sit behind the Explain drawer, keeping the interface clean during exploration.
Class Activity — Can You Hear That?
Year 8/9 · ~50 min · Whole class + pairs
Objective: Identify the boundaries of human hearing; relate frequency to pitch, period, and wavelength; distinguish audible range from infrasound and ultrasound.
Hook (5 min) Without showing the frequency value, play 40 Hz through the class speaker. Ask: “Can you hear that? Can you feel it?” Then jump to 18 000 Hz. Ask who can and cannot hear it. Take a show of hands — results usually split by age. Ask: “What does that tell you about human hearing?”
Guided Exploration (15 min) Teacher-led on the projector. Move through the preset frequencies in order, pausing at each:
- 20 Hz — “This is the lower limit. What do you notice about the waveform?”
- 440 Hz — “This is concert A, the note orchestras tune to.”
- 4 kHz — “This is where the human ear is most sensitive — quieter sounds feel louder here.”
- 20 kHz — “Upper limit. Raise your hand when you can no longer hear it.”
Ask pupils to sketch the spectrum ruler in their books and mark these four reference points.
Pair Investigation (15 min) Each pair works through this task on a device:
Record frequency, period, and wavelength for five frequencies of your choice. Use the metrics bar — do not calculate by hand yet.
| Frequency | Period | Wavelength |
|---|---|---|
Then answer: as frequency doubles, what happens to the wavelength? What happens to the period? Can you spot the pattern?
Calculation Check (8 min) Introduce v = fλ. Ask pupils to pick one row from their table and verify their wavelength using λ = 343 ÷ f. The simulation shows the answer — pupils check their working against it.
Exit Ticket (5 min)
- What is the normal range of human hearing?
- A sound wave has a frequency of 500 Hz. Calculate its wavelength in air.
- Name one use of ultrasound and one source of infrasound.