"The Generation and Propagation of Sound" Sound Phenomenon PPT Courseware 14

Description

"The Generation and Propagation of Sound" Sound Phenomenon PPT Courseware 14

learning target

A preliminary understanding of the conditions for sound generation and propagation

Know that sound is produced by the vibration of objects

The propagation of sound requires a medium, and sound propagates at different speeds in different media.

Know what the echo is about

1. Sound source: the object that makes the sound.

Research activity one

Can you make them sound?

1. Paper jitter

2. Extend the ruler slightly from the table and turn it

3. Pen cover blow

4. A basin of water stirred

Discussion and exchange

1. What are the characteristics of vocalization?

1. Paper sounds in ______;

2. The ruler sounds in ______;

3. When blowing the pen cover, the air inside is ______.

4.When the basin is stirred, the water is ______.

2. What do they have in common?

Sound is produced by objects ______.

All can be used as sound sources.

[Tracking Exercise 1]

(1) How is the buzzing sound produced by mosquitoes flying?

(2) Guitar is the most common stringed instrument. Do you know what it relies on to make sound?

(3) The flute is the most common wind instrument. Do you know what it relies on to make sound?

Research activity two

Place the sounding alarm clock in a glass cover, put foam plastic between the alarm clock and the base of the cover, and gradually extract the air from the cover. What changes do you hear in the sound? Let air enter the cover again. What changes do you hear in the sound?

1. Gradually pull out the air in the hood, and the sound we hear is ________;

2. If you continue to pump air until a vacuum is achieved, there will be a ________ sound;

3. Allow air to enter the cover and _________ the sound.

The scientific method of research: the ideal experimental method

This experiment shows that sound can travel in ________ but not in ________.

[Tracking Exercise 2]

A newspaper reported that "an astronaut saw a meteorite hitting the moon from a distance in space and felt that the sound was deafening." Do you believe?

Answer: There is no air in space, and sound cannot be transmitted or heard in a vacuum, so the news is false.

Exploration activity three

Analyze how sound propagates in the air by observing the changes in horns and candles.

When the sound source is not vibrating, the surrounding air is not vibrating either.

When the sound source vibrates, the surrounding air also vibrates. The vibration of the surrounding air can be seen through the candle flame.

Let’s talk: Do you know any other examples of solid sound transmission?

Crouching: When Indians hunted, they lay prone on the ground and listened to the sounds to predict the coming herds.

Railway guerrillas put their ears on the tracks and can hear the sound of distant trains faster.

Think about it during a 100-meter race on the sports field. In order to keep accurate timing, the timekeeper at the finish line should ()

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

B. Press the stopwatch when you see the white smoke emitted by the starting gun, because your eyes are very sensitive.

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

D. It should be judged by seeing white smoke, because the speed of light propagation is very fast, while the speed of sound propagation is much slower.

Discussion and exchange

1. The propagation speed of sound in various materials is generally _____.

Generally speaking, the speed of sound in _____ > the speed of sound in _____ > the speed of sound in _____

The speed of sound is related to the medium.

2. Normally, the propagation speed of sound in the air is about: _____m/s

For the same medium, the higher the temperature, the higher the speed of sound.

The speed of sound is related to the _____ of the medium.

Knowledge sorting

1. Production of sound

The object that makes the sound is called the sound source.

Sound is produced by the vibration of objects.

The vibrations stop and the sound production stops.

Record the vibration of the sound-emitting body, and when necessary, let the object vibrate according to the recorded vibration rules, which can preserve the sound.

2. Propagation of sound

Sound travels in the form of sound waves

Sound cannot travel through a vacuum.

Solids, liquids, and gases can all transmit sound.

The substance that transmits sound is called the medium of sound.

3.Sound speed

The speed of sound in air at 15°C is 340m/s.

The speed of sound is related to the type and temperature of the medium.

Generally speaking, V solid>V liquid>V gas

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.

Compliance testing

1. As the saying goes: The sound of wind, rain, and reading are all in your ears.

Among them, the sound of wind, rain, and reading are the sounds produced by _____, ______, and _______ vibrations respectively, and these sounds are transmitted through _____.

2. In an experiment to demonstrate that sound is generated by the vibration of an object, the sounding tuning fork is placed close to a light ball under the suspension wire, and the ball is bounced away many times. In this experiment, the role of the ball is ______.

3. There is a large ancient bell in the Confucius Temple in Xi'an. Someone found that when the ancient bell was struck, after the impact stopped, the bell "remained". The main reason is: ( )

A. Echo of bells?

B． The big clock is still vibrating

C. The big clock stopped vibrating, but the air continued to vibrate

D． Prolongation of human hearing

4. When people walk on the shore, they will disturb the fish swimming underwater. The main propagation path of the sound heard by the fish in this process is: ( )

A. Land-Air-Fish B. Land-Air-Water-Fish

C. Land-water-fish D. water - air - fish

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Update Time: 2024-10-19

This template belongs to Physics courseware Lu Jiao edition eighth grade physics volume 1 industry PPT template

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