"Noise and Environmental Protection" Acoustic Phenomenon PPT Courseware 2

Description

"Noise and Environmental Protection" Acoustic Phenomenon PPT Courseware 2

1. Source of noise

1. The meaning of noise

Note: Due to different angles, the meaning of the referred noise is also different.

(1) From a physical point of view: the sound emitted when the sound-emitting body vibrates irregularly

Noise from a physical perspective: it is the sound emitted when the sound-emitting body vibrates irregularly.

(2) From the perspective of environmental protection: any sound that hinders people's normal rest, study and work, as well as sounds that interfere with the sounds people want to listen to.

Please tell me: What noises are there around you?

Practice one practice

The following are noises ( )

A. During class, beautiful singing came from the big speakers in the school.

B. The teacher’s voice during class.

C. The symphony played in the concert hall.

D. The sound of wind and rain imitated by a ventriloquist on the stage.

2. Source of noise

What are the sources of noise in life?

Traffic and transportation noise: horns, whistles, brakes, exhaust sounds, mechanical operation sounds, etc. from various means of transportation.

Industrial noise: noise from textile factories, printing plants, and machine workshops

Construction noise: road construction, building building, piling, etc.

Noise in social life: household noise, noise in entertainment venues, shops, and markets.

2. Noise levels and hazards

1. The classification of noise levels is expressed by decibel (dB) value, which essentially refers to the loudness.

2. Ask students to look at the decibels of sound intensity levels in the table below and recall how they felt in these environments.

To protect hearing, the sound cannot exceed 90dB;

To ensure learning and working, the sound cannot exceed 70dB;

To ensure rest and sleep, the sound should not exceed 50dB;

3. An instrument for measuring noise levels - noise detector.

4. The harm of noise: from the perspective of the physiological and psychological effects of noise on people. Noise also has other hazards. For example, the noise generated by jet aircraft can shatter the window glass of nearby buildings, and the noise can cause "fatigue" and even breakage of work equipment.

Ways to control noise

1. Prevent noise generation - control and install mufflers at the sound source and prohibit honking.

2. Block the transmission of noise-----control sound insulation boards, plant trees and grass (to absorb noise), close doors and windows during the transmission process.

3. Prevent noise from entering human ears - control at human ears: wear earmuffs and cover ears with hands.

Tutorial assessment

1. From the perspective of environmental protection, which of the following statements about music and noise is correct ( )

A. Music is pleasant and enjoyable, but sometimes it can also become noise.

B. Musical sound is the sound produced by musical instruments; noise is the sound produced by machines.

C. Sounds with regular waveforms are musical sounds

D. Musical sound refers to the sound below 40dB, and noise refers to the sound above 40dB.

2. Which of the following sounds is noise? (fill in the serial number)

1) The noise in the self-study class

2) The sound of reading aloud during morning reading

3) The accompaniment of musical instruments when singing

4) The sound of electric drills for house decoration

5) The teacher’s lecture disturbed a student’s drowsiness in class

3. After a heavy snowfall, people felt that everything was quiet outside. The reason is, what do you think is correct ( )

A. It may be that after heavy snowfall, fewer vehicles are used and the noise is reduced.

B. Maybe it’s because after heavy snowfall, the ground is covered with snow and the noise is reflected

C. It may be that the temperature is lower after heavy snow and the noise propagation speed slows down.

D. It may be that it is fluffy and porous after heavy snow, which absorbs noise.

4. The following examples of reducing noise at the sound source are ( )

A. Wear earplugs B. Add a soundproof cover to the machine

C. There is a silencer on the pistol D. Install a soundproof cover

5. The following figure shows the waveforms of two sounds. It can be seen from the figure: Figure (1) is the waveform of _____, and the reason is ____________. Figure (2) is the waveform of _____, the reason is ______________.

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Update Time: 2024-07-06

This template belongs to Physics courseware Beijing Normal University eighth grade physics volume one industry PPT template

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