Waves & Sound
Pipe resonance
Press Play — drive an open pipe at its fundamental; resonance boosts the response.
Pipe resonance — interactive Waves & Sound simulation. Press Play — drive an open pipe at its fundamental; resonance boosts the response. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Pipe resonance
An open pipe resonates when the driving frequency matches a standing-wave mode.
For an open-open pipe, allowed wavelengths satisfy L = nλ/2. At resonance, the amplitude builds because energy is efficiently transferred into the pipe mode.
- fₙ = n·v/(2L)
- Open pipe: λₙ = 2L/n
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
An open-open air column (like an open organ pipe) resonates at a fundamental frequency set by its length. If you use a shorter pipe, does the resonant pitch go up or down?
Predictions to weigh
- A shorter pipe resonates at a lower fundamental frequency.
- A shorter pipe resonates at a higher fundamental frequency.
- Pipe length doesn't affect the fundamental frequency.
Variable roles
What you set:
- Pipe length L (m)
What you measure:
- Fundamental wavelength λ (m)
- Fundamental frequency f₁ (Hz)
How the investigation runs
- Open the pipe-resonance preset and press Reset. The pipe is open at both ends, in 20°C air.
- Enable the fundamental-frequency readout on the pipe.
- Set the pipe length for each trial and record the fundamental frequency.
Governing equation
Open-Pipe Fundamental — f₁ = c/(2L)
An air column open at both ends resonates with a full wavelength fitting twice its length (λ = 2L), giving fundamental frequency f₁ = c/(2L) — the same speed-wavelength relation as any wave, applied to sound in air.
What the printable worksheet asks students to work out
- For one trial, compute f₁ = c/(2L) using c = 331.3·√(1 + 20/273.15) m/s for 20°C air. Compare to the table.
- An open-open pipe's fundamental has a full wavelength λ = 2L. Explain, using v = fλ, why f₁ = c/(2L) follows directly from that wavelength.
Where this shows up beyond the lab
- A pipe closed at one end (like a clarinet) only supports odd harmonics and has fundamental f₁ = c/(4L) — half this experiment's frequency for the same length. Why might closing one end double the effective wavelength?
- The speed of sound c increases with air temperature. If you played this same pipe outdoors on a much colder day, would its resonant pitch go up or down? Why do wind instruments need retuning as temperature changes?
- AP Physics 2 — Unit 14: Waves, Sound, and Physical Optics
- IB Physics — C.4 Standing waves and resonance
- General High School Physics — Waves & sound
- NGSS High School Physics — Wave properties
- Welcome to Pipe Resonance
- Select the pipe
- Press Play
- Drive the fundamental
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.