To Find the Speed of Sound in Air at Room Temperature Using a Resonance Tube By Two Resonance Positions

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The physics practicals play a crucial role in helping the students understand the concepts better by doing them practically. It offers them hands-on experience of how the phenomenon takes place. We provide the complete experiment, how to conduct it, the substitution of values and the further procedure that follows. With the resonance experiment class 11, you can better understand the resonance concepts. We provide these experiments in PDF downloadable form to conduct it easily and quickly while you are at work. 

Experiment to Find the Speed of Sound in Air


To find the speed of sound in air at room temperature using a resonance tube by two resonance positions. 

Apparatus Required for Resonance Experiment Physics:

  • Resonance tube

  • Two-timing forks having frequencies which are known (for example, 512Hz and 480Hz)

  • Rubber pad

  • Thermometer

  • Set squares

  • Water contained in a beaker

  • Plumb line


Consider the length of two air columns for first and second resonance as l1 and l2. Let the frequency of the tuning fork be f. 

Then, the formula is:

ƛ= 2(l2-l1)

The speed of air is calculated using the formula:

𝜈= fƛ

On substituting the value in the formulae, we get, 

𝜈= 2f(l2-l1)

The Procedure of the Resonance Tube Experiment:

  • Make the base horizontal by the levelling screws. Following this, keep the resonance tubes vertical. 

  • Next, in the uppermost position, fix the reservoir R. 

  • Make the pinchcock lose. Fill water from the beaker in the reservoir and metallic tube. 

  • Fix the reservoir in the lowest position, by lowering the reservoir and tightening the pinchcock. 

  • Next, use a tuning fork of higher frequency to experiment. 

  • Vibrate this tuning fork with the help of a rubber pad. Just over the end of the metallic tube, hold the vibrating tongs in a vertical plane. 

  • Next, loosen the pinchcock a bit to allow the water to fall in the metallic tube. When you hear the sound from the metallic tube, lose the pinchcock a bit. 

  • Repeat the above step till you hear the sound with maximum loudness from the metallic tube.

  • By using the set square, against the metre scale, measure the position of the water level. 

  • Decrease the water level by 1 cm. And then tighten the pinchcock. 

  • Again, repeat the above step till maximum loudness is heard. 

  • After this, repeat the steps with a tuning fork of lower frequency. 

  • Record your observations and put them in the resonance tube formula as given below:


The temperature of the air column:

In the beginning:

At the end:

Calculate the mean temperature using the formula:

t= t1+t2/2

f1= frequency of the first tuning fork

f2= frequency of the second tuning fork


Observations from the first tuning fork,

𝜈1= 2f1(l2’-l1’)

Observations from the second tuning fork,

𝜈2= 2f2(l2’’-l1’’)

Calculate the mean velocity using the formula:

𝜈= 𝜈1 + 𝜈2/2


The speed of air at room temperature is ____ m/s.


1. Keep the resonance tube vertical.

2. Ensure that the pinchcock is tight. 

3. Vibrate the tuning fork lightly using the rubber pad. 

4. While vibrating the prongs, ensure that they are vertical at the mouth of the metallic tube. 

5. Carefully read the water level rise and fall. 

6. Use a set square to record the readings. 

Sources of Error:

1. Loose pinchcock. 

2. Resonance tubes might not be uptight. 

3. The air column contains humidity which can lead to an increase in the velocity. 

FAQs (Frequently Asked Questions)

1. On What Principle Does the Resonance Tube Work?

The resonance tube works on the principle of resonance of the air column with a fork.

2. Define the Resonance of the Air Column?

Resonance is considered the phenomenon in which the air column's frequency is equal to the frequency of the tuning fork. 

3. During Vibration, What are the Types of Waves Being Produced in the Air Column?

Longitudinal stationary waves are generated in the air column while measuring the speed of sound at room temperature.

4. What is End Correction?

End correction is defined as the reflection of a sound wave from the end of the tube (slightly above it). 

5. How Do You Find the Velocity of Sound in Air?

It is found using the air column lying above the water surface.

6. What are Some of the Errors that Can Occur While Calculating the Result?

There are two majorly possible errors:

  • If the air enclosed inside is denser than the air outside, it can reduce the velocity of sound. 

  • The velocity of sound can be increased if the air above the column has increased humidity. 

Frequency of tuning fork v(Hz)


No. of observations

Position of water level at resonance

Mean length (mean of three observation in column 4c) l (cm)

Water level falling (cm)

Water level rising (cm)

Mean (cm)






l₁’ = 16.1





l₂’ = 50.3






l₁’’ = 17.3





l₂’’ = 53.9

(Note. The ideal observations are as sample.)

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