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    Measurement of The Speed of Sound in Air

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    عزوز العراقي
    1. This experiment measures the speed of sound in air using resonance in a tube. Tuning forks of varying frequencies are used to excite resonant modes in the air column within the tube. 2. The lengths of the air column at the quarter and three-quarter wavelength resonance positions are measured for each tuning fork. 3. The speed of sound is then calculated for each fork using the relationship between resonant wavelength, frequency, and speed of sound. The average value obtained is taken to be the speed of sound in air.

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    Measurement of The Speed of Sound in Air

    Uploaded by

    عزوز العراقي
    85 views3 pages
    1. This experiment measures the speed of sound in air using resonance in a tube. Tuning forks of varying frequencies are used to excite resonant modes in the air column within the tube. 2. The lengths of the air column at the quarter and three-quarter wavelength resonance positions are measured for each tuning fork. 3. The speed of sound is then calculated for each fork using the relationship between resonant wavelength, frequency, and speed of sound. The average value obtained is taken to be the speed of sound in air.

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    Measurement of the Speed of Sound in Air

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    1. This experiment measures the speed of sound in air using resonance in a tube. Tuning forks of varying frequencies are used to excite resonant modes in the air column within the tube. 2. The lengths of the air column at the quarter and three-quarter wavelength resonance positions are measured for each tuning fork. 3. The speed of sound is then calculated for each fork using the relationship between resonant wavelength, frequency, and speed of sound. The average value obtained is taken to be the speed of sound in air.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    85 views3 pages

    Measurement of The Speed of Sound in Air

    Uploaded by

    عزوز العراقي
    1. This experiment measures the speed of sound in air using resonance in a tube. Tuning forks of varying frequencies are used to excite resonant modes in the air column within the tube. 2. The lengths of the air column at the quarter and three-quarter wavelength resonance positions are measured for each tuning fork. 3. The speed of sound is then calculated for each fork using the relationship between resonant wavelength, frequency, and speed of sound. The average value obtained is taken to be the speed of sound in air.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 3

    MEASUREMENT OF THE SPEED OF SOUND IN AIR

    Apparatus
    1000 ml graduated cylinder, resonance tube, set of tuning forks in the frequency range
    256 Hz to 512 Hz, vernier callipers, metre stick, stand (longest upright type), clamp and
    wooden block.

    Tuning fork A e

    l2
    e A

    A
    l1
    N N

    Graduated cylinder
    Tube
    Water

    Fig.1 Fig. 2

    Procedure
    1. Clamp the tube so that the water in the graduated cylinder closes its lower end.
    The tube should be free to slide vertically through the clamp jaws. Take an
    approximate value of 300 m s-1 for the speed of sound to obtain a rough estimate
    of the quarter wavelength resonance position.
    2. Strike the highest frequency (512 Hz) tuning fork on the wooden block, and hold it
    in a horizontal position just above the mouth of the tube (Fig. 1).
    3. Slide the tube slowly up/down until the note heard from the tube is at its loudest;
    resonance is now occurring.
    4. Tighten the clamp in this position and measure the length of the air column (from
    the water level to the top of the tube) l1 with a metre stick.
    5. Clamp the tube (or its extension) so that the air column is 2 or 3 cm less than 3l1
    (Fig. 2).
    6. Obtain a second weaker resonance with the same tuning fork by again sliding the
    tube until the note heard is at its loudest, at the three-quarters wavelength
    resonance position.
    7. Clamp the tube in this position and measure with a metre stick, the air column
    length l2 at this resonance.

    32
    8. Repeat this procedure to obtain the corresponding values of l1 and l2 for all the
    tuning forks in order of decreasing frequency.
    9. Record the measurements in a table.
    10. Calculate the wavelength using 2(l 2 l1 ) in each case.
    11. Calculate the speed of sound from c f , for each of the tuning forks.
    12. Find the average value for the speed of sound.

    Results

    f/Hz l1/m l2/m /m c/m s-1

    The average value of the speed of sound in air =

    Notes
    The experiment can be done using just one tube. Proceed to obtain resonance as before.
    Measure the length l1. The antinode forms above the top of the tube and so an end
    correction factor has to be added to the length. From theory, it is found that the correction
    factor e = 0.3d , where d is the average internal diameter of the tube (measured using a
    vernier callipers).
    Hence = 4(l1 + 0.3d)
    c=f
    c = 4f(l1 + 0.3d).
    Calculate a value of c for each tuning fork and find an average value for the speed of
    sound.

    If a resonance tube is not available, use 50 cm lengths of 40 mm and 30 mm plastic pipes.

    33
    A specially designed apparatus called a resonometer can also be used to obtain the data.

    e
    l

    Tuning fork Amplifier

    Beginning with the highest frequency tuning fork and a very short column of air, adjust
    the piston until the sound from the vibrating air column is loudest; this is the first
    resonance point. Measure the length l of the air column at resonance. Proceed to use the
    set of tuning forks to complete the data table as in the previous method (it is difficult to
    distinguish resonance for frequencies below 340 Hz).

    = 4(l +e) where e is the end correction factor


    = 4(l + 0.3d) where d is the internal diameter of the tube
    c=f
    c = 4f(l + 0.3d).

    It is also possible to cause resonance in the air column using a signal generator and a
    loudspeaker; the 8 , 5 cm diameter model of loudspeaker is ideal. Clamp the
    loudspeaker in a horizontal position just above the mouth of the tube. Connect the
    loudspeaker to the low impedance output of the signal generator. Gradually increase the
    signal generator frequency from zero until the air column resonates. Calculate the speed
    of sound using the same procedures as before. Repeat the experiment for different lengths
    of the air column.

    34

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