Speed of Sound with a Resonance Tube

Use a water-filled resonance tube and tuning forks to find two resonance lengths for each frequency. From these lengths, determine the wavelength and calculate the speed of sound in air, with or without an end correction.

1. Set up a vertical resonance tube with its lower end submerged in a water reservoir so the air column length can be adjusted smoothly; ensure the tube can slide freely and remains upright.
2. Choose a tuning fork (for example, 512 Hz). Strike it on a wooden block and hold it horizontally just above the tube mouth.
3. Slowly slide the tube to locate the loudest sound (first resonance, approximately quarter wavelength); clamp and measure the air-column length l1 from water level to tube top.
4. Lengthen the air column to just below about three times l1, then slide to find the next loud maximum (third-harmonic resonance, near three-quarters wavelength); clamp and measure the air-column length l2.
5. Repeat the two-resonance measurements for several forks (for example, 512, 480, 426, 384, 341, 320, 288, 256 Hz), recording f, l1, and l2 for each.
6. For each fork, compute the wavelength using lambda = 2(l2 − l1). Taking the difference largely cancels the end correction.
7. Compute the speed of sound for each fork with c = f * lambda, then average the results.
8. Single-resonance alternative: measure the tube’s internal diameter d (vernier calipers), find the first resonance length l1, apply the end correction e = 0.3 d, then use lambda = 4(l1 + e) and c = f * lambda; repeat across forks and average.

Finding the Speed Of Sound with a Tuning Fork HD - Physics Walker:

Speed of Sound Lab - The Physics Channel with Kenny Lee:

📄 MEASUREMENT OF THE SPEED OF SOUND IN AIR - ucc.ie: https://www.ucc.ie/en/media/academic/physics/physicsmainwebsite/outreach/experimentdocuments/leavingcertwrite-ups/MEASUREMENTOFTHESPEEDOFSOUNDINAIR.pdf

• Replace the fork with a signal generator and small loudspeaker above the tube; sweep frequency at fixed l to find resonance, or fix f and vary l.
• Use a sliding-piston resonometer or a snug-fitting plunger in PVC pipe to adjust air-column length precisely.
• Investigate temperature effects.
• Test humidity influence by repeating on a dry vs humid day, noting any systematic shifts in c.
• Plot c from each fork versus f to check for frequency-independent results (consistency check).

• Secure the tall stand and clamp; prevent the tube from slipping and the water cylinder from tipping.
• Manage spills promptly; keep water away from electrical equipment and walkways.
• Strike tuning forks on wood or rubber only; keep fingers clear of vibrating prongs and the tube rim.
• Keep sound levels reasonable when using a loudspeaker; protect hearing as needed.
• Handle glass or plastic tubes and calipers carefully to avoid chips, cuts, or pinches.

• Why use two resonances (l1 and l2) with the same fork? (Using lambda = 2(l2 − l1) cancels most end-correction error, improving accuracy.)
• What is the purpose of the end correction e = 0.3 d? (The displacement antinode forms slightly above the tube mouth, so the effective acoustic length exceeds the geometric length.)
• If f = 512 Hz, l1 = 0.162 m, and l2 = 0.487 m, what is c? (lambda = 2(0.487 − 0.162) = 0.65 m; c = 512 * 0.65 ≈ 333 m s−1.)
• How will a warmer lab affect your result? (Warmer air increases c; roughly +0.6 m s−1 per degree Celsius.)
• What are likely sources of random and systematic error here? (Random: reading lengths, locating maxima, fork decay; Systematic: misreading the water level, not centering the fork, ignoring end correction, parallax.)