"Hazards and Control of Noise" Acoustic Phenomenon PPT Courseware 6

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"Hazards and Control of Noise" Acoustic Phenomenon PPT Courseware 6

Review questions:

1. The three elements of sound are: _______, _______, and _______.

2. The pitch of the sound is determined by the _______ of the sound-emitting body's vibration. The faster the _______, the higher the pitch.

3. Loudness is related to the _______ of the sound emitter. The greater the _______, the greater the loudness.

4. Even if you are blindfolded, you can distinguish the voices of your classmates because each student’s _______ is different.

5. Most people experience sound in the frequency range from _______HZ to _______HZ.

1. Sources of noise:

1. Definition of noise:

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

(1) Noise from a physical perspective:

It is the sound produced when the sound-emitting body vibrates irregularly.

What is the difference between the waveforms of noise and music?

Musical sound: The sound produced when the sound-emitting body vibrates regularly.

Noise: The sound produced when the sound-emitting body vibrates irregularly.

(2) Noise from the perspective of environmental protection:

All sounds that hinder people's work and study, affect people's lives, and interfere with people's hearing are noises.

Please tell me: What are the sources of noise around you?

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.

Make a note

(1) People use decibels to classify sound intensity levels, and the symbol of decibels is dB.

(2) 0dB is the weakest sound that people can hear just now - the lower limit of hearing

(3) In order to protect hearing, the noise should be controlled not to exceed 90dB; to ensure work and study, the noise should be controlled not to exceed 70dB;

In order to ensure rest and sleep, the noise should be controlled not to exceed 50dB.

Noise hazards

Psychological effects: It makes people irritable, lacks concentration, hinders sleep and rest, and affects work efficiency.

Physiological effects: headache, indigestion, blurred vision, deafness, etc., or even confusion, shock or death in severe cases.

Physical effects: High-intensity noise can damage buildings.

On-site training

1. Which of the following statements about noise is incorrect ( )

A. The pleasant music may be noise;

B. Noise is emitted when the machine vibrates during operation;

C. Noise harms people’s physical and mental health;

D. Sounds that interfere with the sounds people want to hear are noises.

2. The ideal sound environment for ordinary people is ( )

A. Like to be in a silent world

B. Like to be in a quiet environment of 30-40dB

C. Like to be in a lively environment with 80-90dB

D. I don’t care even if the environment is above 100dB.

3. In order to ensure work and study, the noise should be controlled not to exceed ( )

A.90dB B.50dB

C.70dB D.30dB

4. When washing clothes in a washing machine, if the clothes are not put away properly, it will cause the washing machine to vibrate violently and make noise. What should be done in this case ( )

A. Wear earplugs or cover your ears to reduce noise in human ears;

B. Close the door to reduce the noise during transmission;

C. Lay your clothes flat to reduce the noise at the source;

D. Stop the washing machine and wash by hand to reduce the noise at the source;

do you know?

In winter, after a heavy snowfall, people often feel completely silent. Do you know why?

The snow that has just fallen is fresh and fluffy. There are many small pores on its surface. When external sounds are introduced into these small pores, they will be reflected. Since the pores are often large inside and small in diameter, only a small part of the sound can be heard. Reflected from the entrance, most of it was sucked away, resulting in a scene of complete silence.

Sound is absorbed by the snow as it travels.

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Update Time: 2024-11-22

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