A method of measuring the speed of sound in the air

The exact method in the Olympiad is:

First, the purpose of the experiment.

1.Learn how transducers work and how they work.

2.The sound velocity was measured by the standing wave method and the phase comparison method, respectively.

2. Experimental instruments.

1 ultrasonic sound velocity measuring device, 1 signal generator and 1 oscilloscope.

3. Experimental procedures.

1.Get ready.

1) Wiring according to the textbook diagram and adjust the distance between the transducers to about 50mm.

2) Find the resonant frequency of the transducer: adjust the output frequency of the signal source and observe the signal amplitude on the oscilloscope, when the amplitude is maximum, the output frequency of the signal source is .

2.The standing wave method measures the speed of sound.

Gradually increase the distance between the transducers, record the data when the amplitude of the observed signal is the maximum, and measure 10 points continuously.

3.Phase comparison method.

According to the wiring diagram, adjust the distance between the transducers to about 50mm, and the output frequency of the signal source is .

Gradually increase the transducer spacing, observe the corresponding Lissajou figure, select the graph as the phase line as the initial state, and record the group of the receiving transducer when there is an oblique line with the slope of the sleeping line, and measure 10 points.

4.Data processing.

1) Calculate the speed of sound from experimental data.

2) Measure the indoor temperature and calculate the theoretical value of sound velocity.

3) Compare the experimental value with the theoretical value, and give the corresponding conclusions.

Fourth, the requirements of the experiment report.

The sound velocity value and uncertainty of the standing wave method and the phase comparison method were calculated by using the difference-by-difference method.

Calculate the theoretical value of the speed of sound.

Compare the results and draw conclusions.

5. Precautions.

Be careful not to short-circuit the output of the signal source.

Oscilloscope measures sound velocity. jpg

Use the oscilloscope to measure the wavelength and so on == to give you the specific steps.

Build a wall in an open field.

Stand at a vertical distance of 100m or 500m from the wall (note the exact distance S) and fire a gun (slap and set off firecrackers, etc., but the sound should be short) and at the same time time hear the echo stop, write down T

Measure the sound velocity several times v=2s t

Main equipment: meter ruler, stopwatch, sounder;

Experimental steps: (1) measure a distance of 500m;

2) When a student starts the pistol at one end and the other student sees the starting pistol smoking, he presses the stopwatch;

3) When you hear the starting gun, press the stopwatch to record the time you hear;

4) Repeat the experiment several times to find the average t of the time

The physical quantities that need to be measured are: (1) measuring a distance s: (2) measuring the time t average from the time of sound to the time of hearing

The expression for calculating the velocity: v=st, substituting the measured value to find the velocity of sound propagating through the air

**As follows: Number of experiments Distance s (m) Time t (s) Average time t Average (s) Speed v m s

One of the simplest and most effective ways to measure the speed of sound is to use the basic relationship between the speed of sound v, the frequency f and the wavelength, that is, a pair of ultrasonic piezoelectric ceramic transducers with the same structure (transmitter and receiver) are used to convert the sound pressure to the voltage.

The amplitude and phase of the ultrasonic wave are observed by using an oscilloscope, the wavelength is determined by the amplitude method and the phase method, and the frequency f is directly read out by the oscilloscope.

Resonant frequency: The ultrasonic piezoelectric ceramic transducer is the key component of the experiment, each pair of ultrasonic piezoelectric ceramic transducers has its own inherent resonant frequency, when the working frequency of the transducer system is in the resonant state, the ultrasonic power emitted by the transmitter is the largest, which is the best working state.

Fundamental quantities in acoustics.

In acoustics, it is the basic quantity in acoustics that describes the characteristics of a sound source and the sound field it generates, or some quantities that play a dominant role in certain acoustic phenomena and effects. Table 1 lists these fundamentals and their interrelationships. Of the first four quantities, sound intensity is the easiest to measure and can be measured very accurately, and the other three can be derived from sound intensity, so it has been mistaken in the past that only sound intensity is the fundamental quantity in acoustics.

The above content refers to: Encyclopedia - Acoustic Measurement.

The speed of sound was measured as follows: Experimental method - Echoes are often heard when singing or shouting in front of high walls or in valleys, and echoes are clearest and loudest in the morning, so this experiment is best carried out in the morning. First of all, choose a suitable experimental site, such as a high wall, with a flat and empty front of the high wall.

The experimenter stands at a distance of r from the high wall and beats the bangs at uniform intervals.

When the first bang sound is heard and the second bang sound is completely overlapped, it means that the time of each bang sound transmitted to the high wall and reflected by the high wall to the experimenter is exactly equal to the time interval t of the bang. Therefore, the velocity of sound propagation v is v=2r t.

Stand at a distance of 100 meters or more from the high wall and bang on the bangs at regular intervals. Take care to control the beat of the bangs so that the bangs reflected off the high walls overlap with the sounds. One of the students standing next to them will report the number of strokes, and the other students will use a stopwatch or watch to time them at the same time.

The time interval t between 20 and 50 strokes was measured, and the time interval t (seconds) of the knock was calculated from the obtained results.

Use a tape measure to measure the distance r (m) from the striking point to the high wall. Substituting the obtained data into the formula v=2r t to obtain the speed of sound vm. Also make a note of the temperature of the air at the time of measurement, as the speed at which sound travels in the air is related to the temperature.

Required [instruments and equipment] bangzi, stopwatch or watch, tape measure.

Precautions] The distance between the experimenter and the wall should be so that the echo can be heard clearly. If every other time a percussion is heard that coincides with an echo, then the formula for the speed of sound v=2r t. Experiment content:

Connect the measuring system. The output of the function signal generator is connected in parallel with the x(y2) input of the transmitting transducer and the oscilloscope, and the output of the receiving transducer is connected to the y1 input of the oscilloscope.

Adjust the resonant frequency. The signal generator outputs a sinusoidal signal, and the frequency is adjusted to the resonant frequency of the transducer, and the resonant frequency f is noted. At this time, the ultrasound emitted by the transducer is the strongest.

The speed of sound is measured using the standing wave method. The output frequency of the signal generator is at the resonant frequency; The operating mode of the oscilloscope is to select the switch to Y1, and the "pull Y1 (X)" knob is advanced. Start with the two transducers about 1cm apart, move the receiving transducer from near and far, observe the change of the received signal on the oscilloscope, and write down the 、...The 20 positions of the receiving transducer when the sine wave maximum is present are the vernier caliper readings L1, L2, L3, 、......l20。

The velocity of sound is measured using the phase comparison method. The output frequency of the signal generator is at the resonant frequency; The oscilloscope's Y-axis operating mode selector switch can be placed in any position, and the "pull Y1(X)" knob is pulled out.

Start with the two transducers about 1 cm apart, move the receiving transducer from near and far, observe the changes in the Lissajou pattern on the oscilloscope, and write down the 、...The 20 positions of the receiving transducer when a straight line occurs, i.e., the vernier caliper readings L1, L2, L3, 、......l20。

The wavelength is obtained by the difference-by-difference method, and then the speed of sound v is obtained. The uncertainty of the sound velocity is calculated, which represents the measurement result.

To estimate the speed at which sound travels through the air, you need to know:

Temperature: Generally at 15 degrees Celsius, the speed of sound is 340 m s, and the speed increases by meters for every 1 degree Celsius increase. So, temperature affects the speed of sound.

Formula: Find Distance: Time * Speed (pay attention to temperature).

Find the velocity (temperature): distance time.

In the measurement of sound velocity, what methods are used to measure the key of the potato ().

a.Simulation and induction.

b.Compensating method and resonance interferometry.

c.Phase comparison method and time difference method.

d.Phase comparison of the digital method and the compensation method.

Correct answer: Phase comparison method and time difference method.

The speed of sound propagation: at room temperature 15°, the speed of sound in solids is about 5200 meters per second, and the speed of sound in liquids is about 1500 meters per secondThe speed of sound in the air is 15 degrees Celsius, about 340 meters per second. For example, the speed at which sound travels in a solid:

Marble 3810m s, Aluminum (rod) 5000m s, Iron (rod) 5200m s; Velocity of liquid propagation: seawater (25) 1531ms, ice 3230ms; The velocity of gas propagation: air (0) 331 m s, air (15 ) 340 m s.

When sound travels in solids, liquids, and gases, it travels fastest in solids and slowest in gases; Among solids, liquids, and gases, solids generally have the highest density and the smallest gases, so of course, the sound wave propagation is the fastest among solids and the slowest among gases. That is, the propagation speed is related to the density of the medium, and the sound velocity is faster when the density is high.

Characteristics of sound propagation:

1.Reflection. Because sound travels at different speeds in different media, the phenomenon of sound reflection and refraction occurs.

The phenomenon of sound waves encountering obstacles while traveling and returning to the original medium is called reflection, and this phenomenon of sound wave reflection is also called echo. The reflection of sound waves was experimentally proven as early as 1882.

2.Refraction. If sound is transmitted in different media, the phenomenon of deflection in the direction of propagation due to different velocities is called refraction.

For example: midnight bell to passenger ship". At night, due to the high temperature near the high altitude and the fast speed of sound, the sound waves will deflect downwards when traveling, so the bell in the Hanshan Temple will be transmitted to the passenger ships on the river.

A vibrating object can emit sound, and the sound emitted by an object can only be propagated to the surroundings by a medium, and the speed at which the sound propagates is different for different media. So, let's design an experiment to measure it together. Experiment 1:

Measuring the speed of sound in the air Equipment: meter ruler (or tape measure) stop table Steps: 1

Stand in an appropriate position in front of a high wall (outdoors) and be able to hear a clear echo as you clap your hands, and your partner will measure your distance to the wall with a ruler. 2.Clap your hands vigorously and then when you hear an echo.

Practice a few times so that the clapping sound and echo are in harmony. 3.Clap continuously for ro times, the partner notes the time of clapping for lo times, and finds the average interval between each adjacent clap (reduce the measurement error, the same below).

4.Divide 2 times your distance from the wall (the distance the sound travels when you hear an echo) by the average interval between each adjacent clapping to get the speed at which the sound travels through the air. Think:

1.How are echoes formed? What are the conditions under which an echo is generated?

2.If the speed of sound propagation in the air is 340 m s, how far away can you be from the wall?