physics resonance tube experiment

Determining the Speed of Sound in Air in a Resonance Tube ( OCR A Level Physics )

Revision note.

Determining the Speed of Sound in Air in a Resonance Tube

Aims of the experiment.

• The aim of the experiment is calculate the speed of sound in air using a tuning fork and a tube of water
• Independent variable = Air level in the tube
• Dependent variable = Length of the air column in the tube where resonance occurs, L
• Temperature of the water
• Frequency of the tuning fork

Equipment List

Apparatus setup to measure the speed of sound in a column of air

• Set up the equipment and fill up the beaker halfway with water
• Place the tube inside the beaker, so the water comes up a quarter of the way. The side of the tube in the water acts as a closed-end
• Hold the tuning fork above the open end of the tube and strike it lightly with the small hammer
• Slowly lower the tube into the water by loosening the clamp until the intensity of sound is amplified
• When resonance (loudest sound) is heard, mark the water level with a rubber band or marker pen. Record this as L 1
• Then, lower the water further until the next point of resonance is heard and mark it. Record this as L 2
• Keep going in this manner as far as possible

Analysis of Results

• The loudness of the sound in the tube from the fork will be small at the node of the sound wave
• The sound will be the loudest at the antinode of the sound wave
• At  L 1 the wavelength is λ / 4
• At L 2 the wavelength is 3 λ / 4
• Therefore, the wavelength of the sound λ is equal to:

λ = 2(L 2 – L 1 )

• Another value of λ could also be found from the distance between  L 3 and L 2 and a mean wavelength can be calculated
• From the wave equation:
• The speed of the sound wave, v , can found from the product of the frequency f of the tuning fork and the wavelength λ calculated

Evaluating the Experiment

• The tuning fork should be struck at the same place above the tube each time
• The tuning fork should be struck with the same force each time
• Make sure the marker is a thin line to get a more accurate reading of the water level
• Submerge the tube into the water slowly, so the antinode of the sound wave (loudest sound) is not missed
• Repeat the experiment to record more reliable readings, since the point where the sound is the loudest is subjective
• Using a resonance tube with a scale will help account for error when measuring the length of the air column within it

Safety Considerations

• Don't let the tuning fork touch the tube, since the vibrations could break or crack it
• Make sure the water is at room temperature, and not too hot or cold
• Make sure no electrical equipment is near the water, otherwise they could be damaged

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• CBSE Class 11
• CBSE Class 11 Physics Practical
• To Find The Speed Of Sound In Air At Room Temperature Using A Resonance Tube By Two Resonance Positions

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

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

Apparatus/Materials Required

• Resonance tube
• Thermometer
• Set Squares
• Water in a beaker
• Two-timing forks of known frequency

Let l 1 and l 2 be the length of the air column for the first and second resonance respectively with a tuning fork of frequency f .

The speed is given by the formula

Substituting, we get

• By making base horizontal with the help of levelling screws, set the resonance tube vertical.
• Fix the reservoir R in the uppermost position.
• Loosen the pinch cock P and fill the reservoir and metallic tube completely with water by a beaker.
• Tighten the pinch cock, lower the reservoir and fix it in the lowest position.
• Take a tuning fork of higher frequency

Observation

The temperature of the air in the air column:

(i) in the beginning ____ °C

(ii) at the end _____°C

The mean temperature is calculated as follows:

Frequency of first tuning fork = f 1

Frequency of second tuning fork = f 2

Calculation

From the first tuning fork,

From the second tuning fork,

The mean velocity at room temperature is given as follows:

At room temperature, the velocity of sound in air is _____ m/s.

1. What is the working principle of the resonance tube?

It works on the principle of resonance of the air column with a tuning fork.

2. What types of waves are produced in the air column?

Longitudinal stationary waves are produced in the air column.

3. Do you find the velocity of sound in air column or in the water column?

The velocity of sound is found in the air column above the water column.

4. What are the possible errors in the result?

The two possible errors in the result are:

(i) The enclosed air in the air column is denser than the outside air, this may reduce the velocity of air.

(ii) The humidity above the enclosed water column may increase the velocity of sound.

5. Will the result be affected if we take other liquids than water?

No, it will not be affected.

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The goal of Unit 11 of The Physics Classroom Tutorial is to develop an understanding of the nature, properties, behavior, and mathematics of sound and to apply this understanding to the analysis of music and musical instruments. Thus far in this unit, applications of sound wave principles have been made towards a discussion of beats , musical intervals , concert hall acoustics , the distinctions between noise and music , and sound production by musical instruments . In Lesson 5, the focus will be upon the application of mathematical relationships and standing wave concepts to musical instruments. Three general categories of instruments will be investigated: instruments with vibrating strings (which would include guitar strings, violin strings, and piano strings), open-end air column instruments (which would include the brass instruments such as the trombone and woodwinds such as the flute and the recorder), and closed-end air column instruments (which would include some organ pipe and the bottles of a pop bottle orchestra ). A fourth category - vibrating mechanical systems (which includes all the percussion instruments) - will not be discussed. These instrument categories may be unusual to some; they are based upon the commonalities among their standing wave patterns and the mathematical relationships between the frequencies that the instruments produce.  

Another common physics demonstration that serves as an excellent model of resonance is the famous "singing rod" demonstration. A long hollow aluminum rod is held at its center. Being a trained musician, teacher reaches in a rosin bag to prepare for the event. Then with great enthusiasm, he/she slowly slides her hand across the length of the aluminum rod, causing it to sound out with a loud sound. This is an example of resonance. As the hand slides across the surface of the aluminum rod, slip-stick friction between the hand and the rod produces vibrations of the aluminum. The vibrations of the aluminum force the air column inside of the rod to vibrate at its natural frequency. The match between the vibrations of the air column and one of the natural frequencies of the singing rod causes resonance. The result of resonance is always a big vibration - that is, a loud sound.

The familiar sound of the sea that is heard when a seashell is placed up to your ear is also explained by resonance. Even in an apparently quiet room, there are sound waves with a range of frequencies. These sounds are mostly inaudible due to their low intensity. This so-called background noise fills the seashell, causing vibrations within the seashell. But the seashell has a set of natural frequencies at which it will vibrate. If one of the frequencies in the room forces air within the seashell to vibrate at its natural frequency, a resonance situation is created. And always, the result of resonance is a big vibration - that is, a loud sound. In fact, the sound is loud enough to hear. So the next time you hear the sound of the sea in a seashell, remember that all that you are hearing is the amplification of one of the many background frequencies in the room.  

Resonance and Musical Instruments

Musical instruments produce their selected sounds in the same manner. Brass instruments typically consist of a mouthpiece attached to a long tube filled with air. The tube is often curled in order to reduce the size of the instrument. The metal tube merely serves as a container for a column of air. It is the vibrations of this column that produces the sounds that we hear. The length of the vibrating air column inside the tube can be adjusted either by sliding the tube to increase and decrease its length or by opening and closing holes located along the tube in order to control where the air enters and exits the tube. Brass instruments involve the blowing of air into a mouthpiece. The vibrations of the lips against the mouthpiece produce a range of frequencies. One of the frequencies in the range of frequencies matches one of the natural frequencies of the air column inside of the brass instrument. This forces the air inside of the column into resonance vibrations. The result of resonance is always a big vibration - that is, a loud sound.

Resonance is the cause of sound production in musical instruments. In the remainder of Lesson 5, the mathematics of standing waves will be applied to understanding how resonating strings and air columns produce their specific frequencies.

This is a simulation of a standard physics demonstration to measure the speed of sound in air. A vibrating tuning fork is held above a tube - the tube has some water in it, and the level of the water in the tube can be adjusted. This gives a column of air in the tube, between the top of the water and the top of the tube. By setting the water level appropriately, the height of the air column can be such that it gives a resonance condition for the sound wave produced by the tuning fork. In the real experiment, resonance is found by listening - the sound from the tube is loudest at resonance. In the simulation, resonance is shown by the amplitude of the wave in the air column. The larger the amplitude, the closer to resonance. Note that at certain special heights of the air column, no sound is heard - this is because of completely destructive interference.

In addition, there is always a node (for displacement of the air molecules) at the water surface. To a first approximation, resonance occurs when there is an anti-node at the top of the tube. Knowing the frequency of the tuning fork, the height of the air column, and the appropriate equation for standing waves in a tube like this, the speed of sound in air can be determined experimentally. What do you get for the speed of sound in air in this simulation?

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

Resonance in an Air Column

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 them easily and quickly while you are at work . 

What is Resonance?

Before jumping directly into the experiment, let’s recall what Resonance is. 

When a person knocks, strikes, strums, plucks or otherwise disturbs a musical instrument, it is sent into vibrational motion at its inherent frequency. Each object's native frequency corresponds to one of the several standing wave patterns that might cause it to vibrate. The harmonics of a musical instrument are commonly referred to as the instrument's inherent frequencies. If another interconnected item pushes it with one of those frequencies, it can be compelled to vibrate at one of its harmonics (with one of its standing wave patterns). This is known as resonance, which occurs when one thing vibrates at the same natural frequency as another, causing the second object to vibrate.

Resonance Tube

A resonance tube (a hollow cylindrical tube partially filled with water and driven into vibration by a tuning fork) is one of our finest models of resonance in a musical instrument. The tuning fork was the item that induced resonance in the air inside the resonance tube. The tines of the tuning fork vibrate at their natural frequency, causing sound waves to impinge on the resonance tube's aperture. The tuning fork's impinging sound waves cause the air within the resonance tube to vibrate at the same frequency.

In the absence of resonance, however, the sound of these vibrations is inaudible. Only when the first thing vibrates at the inherent frequency of the second object does resonance occur. If the tuning fork vibrates at a frequency that is not the same as one of the natural frequencies of the air column within the resonance tube, resonance will not occur, and the two items will not make a loud sound together. However, by raising and lowering a reservoir of water and therefore decreasing or increasing the length of the air column, the position of the water level may be changed so that the air column vibrates with the same frequency of the tuning fork causing the resonance to occur.

Experiment to Find the Speed of Sound in Air

The aim is 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 that are known (for example, 512Hz and 480Hz)

Thermometer

Set squares

Water contained in a beaker

Consider the length of two air columns for first and second resonance as l 1 and l 2 . Let the frequency of the tuning fork be f. 

Then, the formula is

\[\lambda = 2\left ( I_{2}- I^{_{1}} \right )\]

The speed of air is calculated using the formula:

\[ v= f\lambda\]

On substituting the value in the formulae, we get, 

\[v = 2f\left ( I_{2}- I^{_{1}} \right )\]

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 into 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 meter 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:

Observations:

The temperature of the air column:

In the beginning:

At the end:

Calculate the mean temperature using the formula:

\[t = \frac{t_{1}+t_{2}}{2}\]

f 1 = frequency of the first tuning fork

f 2 = frequency of the second tuning fork

Calculations:

Observations from the first tuning fork,

\[v_{1} = 2f_{1}(I_{2}'I_{1}'))\]

Observations from the second tuning fork,

\[v_{2} = 2f_{2}(I_{2}”I_{1}”))\]

Calculate the mean velocity using the formula:

\[v = \frac{v_{1}+v_{2}}{2}\]

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

Precautions :

Keep the resonance tube vertical.

Ensure that the pinchcock is tight. 

Vibrate the tuning fork lightly using the rubber pad. 

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

Carefully read the water level rise and fall. 

Use a set square to record the readings. 

Sources of Error:

Loose pinchcock. 

Resonance tubes might not be uptight. 

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

1. What is the working principle of the resonance tube?

Answer: The idea of the resonance tube is based on the resonance of an air column with a tuning fork. Transverse stationary waves are formed in the air column. The wave's node is at the water's surface, while the wave's antinode is at the tube's open end.

2. What types of waves are produced in the air column?

Answer: The air column produces longitudinal stationary waves. The standing wave is another name for a stationary wave. Standing waves are waves with the same amplitude and frequency travelling in the opposite direction. Longitudinal waves can also generate standing waves.

3. Do you find the velocity of sound in the air column or in the water column?

Answer: The sound velocity is determined in the air column, which is above the water column.

4. What are the possible errors in the result?

Answer: The following are two probable inaccuracies in the result: 

Because the confined air in the air column is denser than the outside air, the air velocity may be reduced.

Humidity in the air above the confined water column may enhance sound velocity.

5. Will the result be affected if we take other liquids than water?

Answer: It will not be altered in any way.

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

1. On what principle does the resonance tube work?

The idea of the resonance tube is based on the resonance of an air column with a tuning fork. Transverse stationary waves are formed in the air column. The wave's node is at the water's surface, while the wave's antinode is at the tube's open end.

2. Define the resonance of the air column?

The phenomenon of resonance is defined as the frequency of the air column is equal to the frequency of the tuning fork. A variable piston adjusts the length of a resonance air column, which is a glass tube. The two subsequent resonances seen at room temperature are at 20 cm and 85 cm in column length. Calculate the sound velocity in the air at room temperature if the length's frequency is 256 Hz.

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. 

( Note. The ideal observations are as samples.)

Teacher Resource Center

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2024 Catalogs & Brochures

Resonance air column.

A sine wave generator drives an open speaker to create a standing sound wave in a resonance tube. The driving frequency and the length of the tube are varied to study their relationship to wavelength and the speed of the sound wave. The concepts of nodes, anti-nodes, and harmonics are investigated for both closed and open tubes.

Grade Level: College

Subject: Physics

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Open Speaker

Designed for the study of wave properties, features a high-quality woofer mounted on a sturdy base with standard banana jack inputs.

Economy Resonance Tube

Two nested cardboard tubes allow students to vary the length of a column of air and study resonance in both open and closed tubes.

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Source Collection: Lab #58

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