"Scientific Inquiry: The Generation and Transmission of Sound" The World of Sound PPT Courseware 4

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"Scientific Inquiry: The Generation and Transmission of Sound" The World of Sound PPT Courseware 4

1. The production of sound

Please do the following experiments together:

1. Shake the pages of the book with your hands to make a sound.

2. Make a sound of "Ah——" and touch your throat with your hands at the same time.

Let me ask you: What did you see when you heard the sound? What did you feel again?

We can find that objects that make sounds are vibrating.

1. All objects that are producing sound are vibrating. When the vibration stops, the sound production also stops.

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

2. Propagation of sound

Next, let’s look at the experiment shown in Figure 3-10 on page 34 of the book.

(Please listen carefully, how does the ringtone change as the air is extracted?)

Experiments have proven that liquids can also transmit sound.

In addition to the experiment you just did, what other examples have you seen or heard in your life that illustrate that sound can propagate in water?

Please do a little experiment:

There are two students at the same table. One student taps the table and the other puts one ear to the other end of the table. What do they hear?

It seems that in addition to gases and liquids, solids can also propagate sound.

Sound can be transmitted through all gas, liquid, and solid materials as media. These materials as transmission media are often referred to as media for short. Sound travels through media.

3. The propagation speed of sound

Please guess which medium in which sound propagates the slowest in solids, gases, and liquids?

Sound propagates at different speeds in solids, liquids and gases. The propagation speed in air at 15°C is 340m/s.

Please calculate, when you go hiking with your classmates, and you shout loudly to your classmates who are 680 meters away from you, how long will it take for them to hear your voice after you speak? What other sounds might you hear?

4. Echo

The echo reaches the ear more than 0.1 second later than the original sound, and the human ear can separate the echo from the original sound.

Question 3: Echo can be used to measure the depth of the seabed and determine the existence of objects in the sea. Please think about what you need to know first to use echo to measure the depth of the seafloor. Then how to calculate?

Answer: The propagation speed of sound in sea water v, and the time t taken from when the sound is emitted to when the echo is received. The calculation formula of seawater depth S is S=1/2vt

practise

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

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

(3) At 15°C, the speed of sound in the air is _________.

(4) Railway workers put their ears against the tracks in order to hear the train in the distance. This is because _________.

(5) Someone shouted to the mountain peak on the opposite side of the valley, and an echo was heard 1.5 seconds later. Can I ask for the distance between the person and the mountain peak?

Summary

1. How does sound occur?

2. The propagation of sound depends on the medium (gas, liquid, solid).

3. The propagation speed of sound in different materials is different.

The speed of sound in air at 15℃ is v=340m/s

4. Knowledge related to echo

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Update Time: 2024-10-01

This template belongs to Physics courseware Shanghai Science Edition 8th Grade Physics industry PPT template

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