Engineering activity
Sound Amplifier
Roll paper into a cone shape and talk through it. Does it make your voice louder? Explore how shapes can change sound!
Materials and setup
- paper cups
- cardboard tubes
- tape
- scissors
- paper
How this changes by age
Pre-K (ages 3–4)
Roll paper into a cone shape and talk through it. Does it make your voice louder? Explore how shapes can change sound!
Steps
- Roll a piece of paper into a cone (like a megaphone). Tape it so it stays.
- Talk into the small end. Can someone across the room hear you better?
- Try whispering without the cone, then with the cone. Which is louder?
- Cup your hands behind your ears. Does that help you hear better?
- Try different cone sizes. Does bigger mean louder?
- Tell a grown-up one thing that surprised you.
Learning objectives
- Discover that cone shapes can make sounds louder
- Compare sound volume with and without an amplifier
- Explore how shape affects the direction of sound
Kindergarten (ages 5–6)
Build a phone speaker amplifier from a cup or cardboard tube. Test different shapes to find which makes your music the loudest.
Steps
- Cut a slot in a paper cup just big enough for a phone to stand in (parent helps).
- Play music on the phone at a set volume. Listen from 5 feet away.
- Place the phone in the cup. Listen again from 5 feet away. Is it louder?
- Try a cardboard tube instead of a cup. Is that louder or quieter?
- Try a tube with a cone on the end (like a trumpet). Is that the loudest?
- Draw your three designs and rank them from quietest to loudest.
- Tell a grown-up one thing that surprised you.
Learning objectives
- Build multiple sound amplifier designs and compare their effectiveness
- Discover that hollow shapes can amplify sound
- Rank and compare designs based on observed volume
Early elementary (ages 6–8)
Engineer a phone speaker amplifier optimized for maximum volume. Test how shape, material, and opening size affect amplification.
Steps
- Build 3 amplifier designs: cup, tube, and horn (tube with expanding cone end).
- Test each by playing the same song at the same volume. Rate loudness 1-5 from a fixed distance.
- Test materials: paper cup vs plastic cup vs styrofoam cup. Does material matter?
- Test cone opening size: small, medium, and large horn opening. Rate each.
- Test resonance: try different tube lengths. Does length change the sound quality?
- Combine your best findings into one ultimate amplifier. Rate it against your first design.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Investigate how shape, material, and size affect sound amplification
- Understand that sound waves bounce and concentrate inside hollow shapes
- Optimize a design by systematically testing and combining the best features
Upper elementary (ages 8–10)
Design acoustic amplifiers exploring resonance, horn geometry, and sound reflection. Measure volume with a decibel meter app and calculate amplification gain.
Steps
- Research acoustic amplification: resonance chambers, horn speakers, parabolic reflectors.
- Build 4 designs: simple cup, tube, exponential horn (cone that widens gradually), and parabolic reflector (bowl shape).
- Use a free decibel meter app to measure sound level from the same distance for each design.
- Record the phone's raw volume (dB) and each amplifier's output (dB). Calculate gain: amplified dB - raw dB.
- Test how distance affects amplification. Measure at 3 feet, 6 feet, and 10 feet.
- Research how gramophone horns and stadium speakers work using the same principles.
- Write a report on the physics of acoustic amplification with data from your experiments.
- In one sentence, tell a parent or sibling what surprised you today.
Learning objectives
- Measure and calculate acoustic amplification gain in decibels
- Compare the effectiveness of different acoustic geometries (cone, tube, parabola)
- Connect experimental acoustic principles to real-world speaker and amplifier design
Safety and evidence note
Read the full activity before beginning. An adult should supervise tools, heat, food, outdoor work, movement, and experiments as appropriate. Completion records that the activity was done; the child’s explanation, work sample, photo, or demonstration is stronger evidence of learning than a completion check alone.
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