"The Generation and Propagation of Sound" Sound Phenomenon PPT courseware download

"The Generation and Propagation of Sound" Sound Phenomenon PPT courseware download

Part One: Guidance Design

Learning point 1: The production of sound

Experiment 1: Put your finger on the speaker of the radio that is playing music, and you will feel the speaker and body vibrating. (As shown in Figure 2-1-7A)

Experiment 2: When the guitar strings are plucked to make a sound, the small pieces of paper placed on the strings will be bounced away by the strings. (As shown in Figure B)

Experiment 3: Insert the sounding tuning fork into the water and it will splash. (As shown in Figure C)

Summary: Sound is produced by the _______ of an object.

Learning Point 2: Propagation of Sound

Experiment 1: As shown in Figure 2-1-8, place a small alarm clock in a sealed glass cover and adjust it to the ringing state. The ringing can be heard clearly. What will happen if you use an air extractor to gradually remove the air from the glass cover? Stop pumping, open the valve, and let air enter the glass cover. How will the ringtone change?

What inspiration do you have?

Answer: The alarm clock tone first becomes smaller and then becomes louder after opening the valve. This shows that the propagation of sound requires a medium, and sound cannot be transmitted in a vacuum.

Experiment 2: As shown in Figure 2-1-9A, Xiaohong placed the watch on the desk and put her ear to the table. She could hear the clear "ticking" sound of the watch, which shows that ______ can transmit sound; as shown in Figure B, Xiao Ming put two stones in the water and hit each other. He could also hear the impact sound, which shows that both ________ and ______ can transmit sound.

Learning Point 3: Speed ​​of Sound

Carefully analyze the data in the table below. What do you find?

think:

Question 1: The ratio of the distance a sound travels to the time it takes to travel is called _______.

Question 2: The speed of sound propagation is related to the ______ and ______ of the medium. Generally speaking, v solid _____ v liquid _____ v gas, the higher the temperature, the speed of sound _____.

Sound Generation and Propagation PPT, Part 2: Application Examples

Type 1 sound production

Example 1: In order to explore the causes of sound, Xiao Ming and Xiao Hua did the following experiment together: As shown in Figure 2-1-3A, Xiao Ming put his hand on his throat and spoke loudly, and felt his larynx vibrating; as shown in Figure B , Xiaohua put the sounding tuning fork in the water, and the water surface stirred up splashes. By analyzing these two experimental phenomena, the conclusion you can draw is: _______________________. Xiaohua's classmate hit the table hard with her hand, and the table made a loud noise, but she almost didn't see the vibration of the table. In order to clearly see the experimental phenomenon, your improvement method is: __________________________________________________.

[ Analysis The vibration amplitude of some sounders is small and difficult to observe. The conversion method can be used to display it. For example, sprinkle some small objects such as scraps of paper or fine sand on the knocked table, and the sound will be reflected by the beating of the small objects. The desktop is vibrating.

[Method Guidance]Conversion Method

In physics, for some invisible and intangible phenomena or physical quantities that are difficult to measure directly, we usually use some intuitive phenomena to understand or indirectly measure them with easy-to-measure physical quantities. This method of studying problems is called the conversion method.

Type 2 Sound Propagation

Example 2 2017·Liuzhou Which of the following statements about sound is correct ()

A． Sound can only travel in the air

B. The propagation speed of sound in vacuum is 3×108 m/s

C. Sound is produced due to the vibration of objects

D. As long as an object vibrates, we can hear sound

[ Analysis Objects are all vibrating, so C is correct; vibrating objects can make sound, but we may not be able to hear the sound emitted by the vibration of the object. If there is no medium, the loudness is too small, and the vibration frequency is not within the range of human hearing, we No sound is heard, so D is wrong.

[Error-prone warning] (1) Sound is produced by the vibration of objects. The propagation of sound requires a medium, and sound cannot be transmitted in a vacuum. Therefore, if there is sound, there must be vibration, but if there is vibration, you may not be able to hear the sound, such as the vacuum bell experiment.

(2) When the object stops vibrating, the sound stops, but the sound does not disappear immediately. The sound that has been emitted will still propagate in the medium, so when the vibration stops, we may still hear the sound.

Example 3 In order to verify that "the propagation of sound requires a medium", Xiaohua designed a set of ingenious experimental devices: hang up his father's mobile phone with a thin wire in a wide-mouth bottle, and fix the end of the wire on the cork of the bottle mouth. The air inside can be extracted through the glass tube at the mouth of the bottle, as shown in Figure 2-1-4.

(1) When Xiaohua was not pumping, he used his home phone to call his cell phone. He ________ (optional "can" or "can't") heard the ringtone of his cell phone.

(2) Xiaohua dialed his cell phone while he was constantly pumping air out. The ring tone he heard was ____________________.

(3) Through the comparison of the above experiments, Xiaohua concluded that: ____________________.

[ Analysis The ringing is getting smaller and smaller, and you can't even hear the sound, that is, the vacuum cannot transmit sound.

[Experimental Instructions]In the experiment to explore whether sound can propagate in a vacuum, scientific reasoning was used. The air extractor cannot remove the air from the glass bottle, but as the air in the glass bottle continues to decrease, the sound heard becomes smaller and smaller. From this reasoning, it can be seen that if the air in the glass bottle is gone, we will not hear the sound. That is to say, it can be concluded that sound cannot be transmitted in a vacuum.

PPT on the production and spread of sound, part 3: classroom feedback

1. These phenomena shown in Figure 5-1 illustrate that: the objects that are making sounds are ________; the vibration stops and the sounds are ________. In the experiment, since the vibrations of the drum skin, trumpet, and tuning fork are not easy to be directly observed, the method in the picture is used, which is called the ________ method.

2. As shown in Figure 5-2, if the small electric bell that is making sound is placed in a closed glass cover connected to the air extractor, then:

(1) In the process of gradually extracting the air from the glass cover with an air extractor, the sound heard will gradually ________.

(2) This experimental phenomenon shows that the propagation of sound requires ________.

(3)The physical method used in this experiment is ________.

3. Point out what sound propagates in the following situations (optional "solid", "liquid" or "gas").

(1) Put your ear against the pillow and you can hear the "ticking" sound of the mechanical watch placed under the pillow: ________.

(2) Use a taut wire to connect a "rustic telephone" made of two small matchboxes to carry out a conversation: ________.

(3) People usually talk face to face: ________.

4. Sound travels at different speeds in different media. According to the following information, it can be seen that in most cases, the propagation speed of sound in gas is ________ (please fill in "larger" or "smaller") than in liquid. The propagation speed of sound in air is affected by ________.

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