"The Use of Sound" Sound Phenomenon PPT Courseware 12

Description

"The Utilization of Sound" Sound Phenomenon PPT Courseware 12

Review before class

1. How is sound produced? What is the speed of sound?

Sound is produced by the vibration of objects.

The speed of sound is used to describe how fast sound travels.

The magnitude is equal to the distance that sound travels per second.

2. What is the frequency range in which people can hear sounds? What is ultrasound? What are infrasound waves?

Sound: 20Hz-20000Hz sound

Ultrasound: sound above 20000Hz

Infrasound: Sound below 20Hz

learning target

Understand the ability of sound to transmit information and energy and its applications in modern technology.

Navigation of this section

1. Sound and information

1. Sound can convey information

2. Echolocation and sonar

3.B-ultrasound

2. Sound and energy

1. Sound can transmit energy

2. Clean watches and other fine machinery

3. Remove stones from human body

"B-ultrasound"

Ultrasound waves are emitted into the pregnant woman's body. The ultrasound instrument receives and measures the reflected sound waves. The reflected waves are processed and displayed on the screen, so that the baby's development can be known.

Choose one

The medical B-ultrasound machine uses ultrasound waves to diagnose conditions, but people cannot hear the sound it makes. This is because ( )

A． The loudness of the sound is too low

B. The sound is too loud

C． The frequency of sound is lower than the frequency of sound that humans can hear

D. The frequency of sound is higher than the frequency of sound that humans can hear

2. Echolocation: Determine the location and distance of the target based on the direction and time of the arrival of the echo. For example: bats foraging, using sonar to detect ocean depth, "B-ultrasound", etc.

The working principle of sonar: echolocation, that is, using a transmitter to emit ultrasonic pulses, and the sonar instrument detects the reflected sound waves, so that the depth of the seabed h=1/2vt can be calculated

Consolidation exercises

1. Place two identical tuning forks side by side (without contact), with the ping pong ball leaning against tuning fork B. When tuning fork A is struck, you will find that the ping pong ball _________, which illustrates _________.

2. The following are not the use of acoustic information ( )

A. The rumble of thunder in the distance indicates a possible heavy rain.

B. Doctors use B-ultrasound to observe people’s physical condition

C. Surgeons use ultrasound to remove stones from the human body

D. When choosing a porcelain bowl, experienced people always knock it to distinguish the sound quality.

Compliance testing

1. Have you read Jin Yong’s martial arts novels? The "lion's roar" Kung Fu described in it can use sound waves to kill the opponent. Let's analyze what characteristics such a sound may have: ①________, ②________. This kind of kung fu uses sound to convey ________.

2. As shown in the picture, a glass is placed between two tuning forks. When the tuning forks made a sound, we found that the glass was shattered. This shows that sound has ________. What can we do in life by using this characteristic of sound? application? Please give an example________ (just give one example)

3. Which of the following statements is incorrect ( )

A． Strong ultrasonic waves are commonly used to drill and cut gemstones

B. Infrasound waves generated during earthquakes can be heard by some animals but not by humans.

C． In shipwreck salvage, sonar is used to locate sunken ships and measure sea depth.

D. Ultrasound can be used to predict earthquakes, detect typhoons and nuclear explosions in the atmosphere

Analysis of typical cases 1

During a military exercise, a destroyer used sonar technology to discover an enemy submarine staying in the deep sea directly below it. The command center ordered an immediate attack. It is known that the time it takes for the sonar to emit a sound wave and receive the reflected echo is 0.74 seconds. ask:

What should be the depth of a bathymetric explosion used in an attack? (The speed of sound in sea water is 1531m/s)

Analysis: This is the military application of sound knowledge. The explosion depth of the depth bomb used in the attack is the depth of the enemy submarine detected by sonar.

Solution: According to the question, the distance traveled by the explosion sound of the depth charge is:

S sound = v sound t = 1531m/s×0.74s=1132.94m

Therefore, the explosion depth is:

h= S sound/2=1132.94/2=566.47m

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Update Time: 2024-11-20

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

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