Velocity of Sound in Air using Resonance Tube
What you will learn
Determine the speed of sound in air at room temperature using a resonance column tube apparatus and a set of standard tuning forks of known frequencies.
Materials needed
- Resonance Tube Apparatus with water reservoir and pinch cockWhat is it?Resonance Tube Apparatus with water reservoir and pinch cock₹50
One-meter vertical borosilicate glass tube mounted on polished wooden stand with millimeter scale and leveling screws.
Specifications- Tube Length
- 100 cm (1 meter)
- Internal Diameter
- 25 mm precision bore
- Scale
- 0 – 100 cm graduated in 1 mm
- Reservoir
- Brass reservoir with fine height adjust clamp
- Set of Tuning Forks of known frequencies (256 Hz, 384 Hz, 480 Hz, 512 Hz) setWhat is it?Set of Tuning Forks of known frequencies (256 Hz, 384 Hz, 480 Hz, 512 Hz) set₹95
Set of 5 matched frequency steel acoustic tuning forks stamped with nominal frequencies.
Specifications- Frequencies
- 256, 341.3, 384, 480, 512 Hz
- Material
- High-carbon forged acoustic tool steel
- Accuracy
- ± 0.2% calibrated at 20°C
- Finish
- Nickel chrome plating
- Rubber Striking Pad / MalletWhat is it?Rubber Striking Pad / Mallet₹140
Hard vulcanized rubber striking block for exciting clean fundamental harmonic vibration.
Specifications- Dimensions
- 75 mm × 50 mm × 25 mm
- Durometer
- 60 Shore A vulcanized rubber
- Base
- Weighted wooden anti-slip base
- Laboratory Thermometer (0-50°C)What is it?Laboratory Thermometer (0-50°C)₹185
Standard laboratory apparatus used in Velocity of Sound in Air using Resonance Tube.
Specifications- Category
- Physics Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Metre scale & Plumb lineWhat is it?Metre scale & Plumb line₹230
Standard laboratory apparatus used in Velocity of Sound in Air using Resonance Tube.
Specifications- Category
- Physics Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
- Water jugWhat is it?Water jug₹275
Standard laboratory apparatus used in Velocity of Sound in Air using Resonance Tube.
Specifications- Category
- Physics Apparatus
- Grade
- CBSE / NEP 2020 Laboratory Standard
Tick items as you collect them. Tap + to see the product, specifications and buy options.
Stay safe
- Never strike the tuning fork on metallic or hard surfaces; use only the rubber pad.
- Hold vibrating prongs horizontally along the tube diameter without touching the glass rim.
- Locate the resonance peak carefully by raising and lowering the water meniscus around the maximum.
- Record room air temperature to correct the experimental sound velocity to 0°C (v0 = vt - 0.61t).
Steps
- 1Level the resonance tube apparatus and fill the reservoir with clean water.Observation
Fill reservoir with clean water; adjust height to bring water meniscus close to top of resonance tube.
SafetyClamp water reservoir securely; do not let rubber hose kink or spill.
- 2Strike the tuning fork of highest frequency (e.g. 512 Hz) against the rubber pad to set its prongs in vibration.Observation
Strike 512 Hz tuning fork gently on a soft rubber strike pad; hold vibrating prongs horizontally over tube mouth.
SafetyNever strike tuning fork against hard metal or table corners; this damages harmonic calibration.
- 3Hold the vibrating prongs horizontally about 1 cm above the open end of the glass resonance tube.Observation
Lower water level gradually while listening attentively; loud acoustic resonance roar occurs at l1 = 16.0 cm.
SafetyDo not touch vibrating tuning fork prongs against the glass tube rim.
- 4Slowly lower the water level by releasing the pinch cock until a loud sound (first resonance) is distinctly heard.Observation
Continue lowering water column until second loud resonance maximum booms at l2 = 49.5 cm.
SafetyVerify water column surface is stationary before taking length reading on millimeter scale.
- 5Pinpoint the water meniscus reading for first resonance length (l1).Observation
Difference l2 - l1 = 33.5 cm gives half-wavelength λ/2; full wavelength λ = 0.670 m.
SafetyDry tuning forks immediately after use with clean cloth to prevent rust.
- 6Lower the water level further until the sound swells loudly again at the second resonance position (l2 ≈ 3l1).Observation
Calculated speed v = 2 × 512 × 0.335 = 343.04 m/s matches standard acoustic velocity at 20°C.
SafetyEmpty water reservoir before packing away apparatus.
- 7Calculate velocity v = 2f(l2 - l1) which eliminates end correction (e = (l2 - 3l1)/2). Repeat for two other tuning forks.
Tap + on a step to see what you will observe and any safety tips.
Record your observations
| Tuning Fork Frequency f (Hz) | First Resonance Length l1 (cm) | Second Resonance Length l2 (cm) | l2 - l1 (cm) | Sound Velocity v = 2f(l2-l1) (m/s) |
|---|---|---|---|---|
| 512 Hz | 16.0 cm | 49.5 cm | 33.5 cm | 343.04 m/s |
| 480 Hz | 17.1 cm | 52.8 cm | 35.7 cm | 342.72 m/s |
| 384 Hz | 21.5 cm | 66.1 cm | 44.6 cm | 342.53 m/s |
| 341.3 Hz | 24.2 cm | 74.4 cm | 50.2 cm | 342.66 m/s |
| 256 Hz | 32.3 cm | 99.3 cm | 67.0 cm | 343.04 m/s |
Tap a highlighted cell to write your own observation.
Result and conclusion
First and second resonance air column lengths yield sound velocity v = 2f(l2 - l1) = 343.4 m/s at 22°C, matching theoretical acoustic speed within 0.8% error.
| Observation | What it means |
|---|---|
| End Correction Elimination | Subtracting resonance lengths (l2 - l1 = λ/2) completely eliminates fictitious antinode end correction error e. |
| Harmonic Relationship Verified | Second resonance occurs at approximately 3× the first resonance column length (l2 ≈ 3·l1). |
| Temperature Normalized Speed | Measured velocity v = 343.0 m/s at 20°C normalizes via v0 = v / √(1 + t/273) to 331.3 m/s at 0°C. |
| Acoustic Antinode Position | Calculated end correction e = (l2 - 3·l1)/2 = 0.75 cm matches theoretical 0.3 × tube inner diameter. |
Sample readings. Replace with your own results.