"The Generation and Propagation of Sound" PPT courseware on acoustic phenomena

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"The Generation and Propagation of Sound" PPT courseware on acoustic phenomena

production of sound

Experiment 1: Place two fingers gently on the throat and make a sound.

What did you notice? __________ You know what vibrates? ___________

Experiment 2: Strike the tuning fork, hear _______, and find the tuning fork ________.

Hold the tuning fork with your hand and the tuning fork stops vibrating. Can you still hear the sound? _______

Based on the above phenomena, think about what common characteristics objects have in common when they make sounds?

1. The production of sound

get conclusion:

1. Sound is produced by the vibration of an object. When the vibration stops, the sound production also stops.

2. Sound source: The object that is making sound is called the sound source.

Experiment 3: When a sounding tuning fork touches the water surface, what will happen ____________? When a sounding tuning fork touches a hanging table tennis ball, what will happen ____________. Conclusion: From the above phenomenon, it can be concluded that what kind of movement is the tuning fork doing? __________

Thinking: What role does table tennis play in the experiment?

Amplify the tiny vibrations of the tuning fork for easy observation.

We use transformation methods to indirectly express phenomena that are not easily observed.

common sense:

How some animals make sounds:

Most birds: The song membrane in the abdomen vibrates.

Bee: The "buzzing sound" produced by the vibration of its wings.

Cricket: It is also the "sound" produced by the vibration of wings.

How some instruments sound:

Erhu: The sound is produced by vibrations caused by the friction between the bow and the strings.

Flute: The sound is produced by the vibration of the air inside the tube.

2. Propagation of sound

1. Sound can spread in ______, but it cannot spread in _______.

Can you find an example of sound traveling through the air?

2. Both solids and liquids can transmit sound

Thinking: Can sound propagate in solids and liquids? Please give an example?

Can liquids and solids also transmit sound? Do you have relevant life experience to answer this question?

Summary: Sound is propagated through solid, liquid, gas and other substances as media; sound cannot be propagated in a vacuum.

——The propagation of sound requires materials

——These substances are called media

3. The propagation speed of sound

Speed ​​of sound: The speed at which sound travels is called the speed of sound.

Please guess, when sound propagates in solids, gases, and liquids, which medium does it propagate the fastest and which is the slowest?

basic exercises

(1) All objects that are making sounds are ___________.

(2) Sound must be transmitted by ______, it cannot be transmitted in ______

(3) Normally, the speed of sound in air is ____________.

(4) Railway guerrillas put their ears against the railway tracks in order to hear the sound of distant trains more quickly. This is because ____________________.

5. During the 100-meter race on the sports field, the timekeeper at the finish line should ( )

A. Press the stopwatch when you hear the gunshot, because your ears are sensitive to hearing

B. See the white smoke emitted from the starting gun and press the stopwatch at the same time because your eyes are very sensitive

C. Depending on your own control, you can press the stopwatch when you hear gunshots and see white smoke, because gunshots and white smoke occur at the same time.

D. It should be judged by seeing white smoke, because the propagation speed of light is much faster than the speed of sound.

passing questions

1. Among the following media, the fastest sound propagation speed is ( )

A. water b. vacuum c. iron d. Air

2. Place the radio that is playing music in a vacuumed glass cover. At this time, you can hardly hear the music. This is mainly because ()

A. The speaker of the radio stops vibrating B. Sound cannot travel through a vacuum

C. The sound is blocked by the glass D. Solids cannot transmit sound

3． Which of the following statements is wrong ( )

A. The sound of a drum is caused by the vibration of the drum head

B. In the 100-meter race, the finish timer should start timing when he hears the gunshot.

C. Maritime survey ships can use echo to measure sea depth

D． When there is thunder in summer, we often hear the roar of thunder, which is caused by multiple reflections of thunder.

4. If the timer at the 100-meter finish line at a sports meeting starts timing when he hears the gunshot, then ( )

A. The results are better than the actual ones. B. The results are worse than the actual ones.

C. The results are consistent with the actual results D. Unable to judge

think sound

What scientific knowledge about sound does the following experiments and examples demonstrate?

①Put some paper scraps on the drum surface. When you beat the drum, you can observe the paper scraps beating and hear the sound of the drum.

Sound is caused by the vibration of objects.

② When a mobile phone is placed in a vacuum cover, when there is an incoming call, only the indicator light flashes and no ringing sound is heard.

Sound cannot travel in a vacuum.

③"The sound of wind, rain and reading are all in my ears"

Gases, liquids, and solids can all be used as sound sources, and air can transmit sound.

④ When the gong is sounding, hold down the gong with your hand and the sound will disappear.

The vibrations stop and the sound production stops.

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Update Time: 2024-11-23

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 1 industry PPT template

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