Speed of sound (resonance tube)

A/L Physics · G.C.E. Advanced Level · Grades 12–13

Aim

To find the speed of sound in air using a resonance tube.

Apparatus

• A resonance tube and water reservoir
• Tuning forks (256, 320, 384, 480 Hz)
• Metre rule

Method

1. Sound the fork above the mouth of the tube.
2. Lower the water to find the first resonance L₁.
3. Find the second resonance L₂.
4. Calculate λ = 2(L₂ − L₁) and v = fλ.

Conclusion

v = 2f(L₂ − L₁) gives ≈ 343 m s⁻¹ for every fork; using L₂ − L₁ removes the end correction.