20 years of teaching

Chapter 219 Are You Well?
Lin Feifan hit the tuning fork again, put it into the washbasin for the first time, and immediately the water splashed everywhere...

Water splashed on Wang Qinqin's face.

The students around burst into laughter, Wang Qinqin quickly retracted her neck, wiped the water off her face in embarrassment, stared at Teacher Lin, pursed her mouth, her eyes were watery...

snort!Did you do it on purpose?Teacher Lin, how are you?

Before the other students stopped laughing, Lin Feifan asked Wang Qinqin in a very low voice: "Are you in good health?"

Wang Qinqin blushed immediately and nodded.

Ask this question in class, Mr. Lin, you are really bad!

It's been so long, how can it not be better?Good morning.

There is a reason why Wang Qinqin is shy...

In the first physical education class at the beginning of the school year, Wang Qinqin asked for leave on the grounds of a stomachache to avoid physical education.

In the second physical education class, Wang Qinqin said she had a stomachache and asked for leave, but Lin Feifan disagreed, saying that she had to go to physical education because of the stomachache.

That physical education class had a lot of training. Halfway through the class, Wang Qinqin was pale, gasped for breath, and couldn't even stand up when she was sitting on the ground.

Lin Feifan found that something was wrong, and asked with concern: "What's the matter?"

Wang Qinqin said aggrievedly: "I really have a stomachache."

Immediately, Lin Feifei felt very guilty, and personally sent Wang Qinqin to the dormitory to rest, and even went to pour a cup of hot water for Wang Qinqin to drink.

During the third physical education class, Wang Qinqin had already fallen in love with physical education class, so she didn't ask for leave anymore, and came on her own initiative.

Lin Feifan was worried, and asked worriedly, "Wang Qinqin, does your stomach hurt?"

At that time, Wang Qinqin replied: "How can I have a stomachache all the time? It's better soon."

But today, in front of so many people, Mr. Lin is still asking if he is in good health. Didn't they say he was well?Teacher Lin, do you still not believe me?

Wang Qinqin lowered her head, a little distracted...

You really can't lie. When a liar tells the truth, no one will believe it...

Lin Feifan stretched out his hand and pressed it down like a palm, and the classroom immediately fell silent.

Sitting in the back, Wang Boda imitated this movement. He thought it was very chic and beautiful, and he wanted to use this movement to remind the students to be quiet during class.

Li Tuanjie, who was listening attentively, also remembered this action in his heart. He felt that this action was really effective...

Lin Feifan asked: "Students, do you know what I was talking to Wang Qinqin just now?"

Everyone shook their heads. They did see Teacher Lin interacting with Wang Qinqin, but they didn't hear what he was talking about.

Chief Yang's eyes widened, he was puzzled, he whispered to the girl and made it public, and asked everyone if they heard the content. Is this also part of the class?Is this part necessary?
Lin Feifan continued: "Wang Qinqin is very close to me, and she heard what I said, but you who are farther away from me did not hear it, so it shows that the loudness of the sound heard by people is not only related to the amplitude of the sounding body, but also related to the sound. What is it about? Liu Mingfeng, tell me."

The big man Liu Mingfeng scratched his scalp. He is usually a big bum, but he looked very shy in physics class, and said cautiously: "It also has something to do with the distance from the sound source."

"The answer is correct, please sit down!" Lin Feifei continued to explain, "The farther away from the sound source, the lower the loudness, which is related to the degree of concentration of the sound waves. got smaller."

So how do you increase the loudness?
In addition to increasing the vibration amplitude of the sound source and getting closer to the sound source, are there other methods?
Lin Feifan suddenly called out: "Ms. Li, are you hungry?" His voice was relatively low.

The students all looked back with a smile.

This made Li Tuanjie flustered all of a sudden, he didn't hear what Lin Feifan said clearly, he only knew it was aimed at him.

I have been listening to the class carefully, why was I criticized by name?

Lin Feifan clasped his hands into a trumpet shape, pointed in the direction of Li Tuanjie, and shouted deliberately: "Mr. Li, are you hungry?"

The sound is so loud!
Haha, it turned out to be to cooperate with the demonstration experiment!

Li Tuanjie waved his hands and smiled: "Not hungry, not hungry, listening to Mr. Lin's class, forgetting to eat and sleep, will you be hungry?"

Lin Feifan concluded that the sound transmission through the horn-shaped tube can reduce the dispersion of the sound and achieve the purpose of increasing the loudness.

Loudness is also known as volume or sound volume. The unit of measurement is decibel, and the symbol is dB. 0dB does not mean that there is no sound at all, but the lower limit of human hearing, which is the weakest sound that people can just hear.

The ideal quiet environment for people is 30-40dB, not the quieter the better.

Scientists once conducted an experiment in which a person was sealed in a very quiet environment, and materials with good sound insulation performance were used to prevent external sounds from entering.

At the beginning, this person was very calm, he could read a book leisurely, and seemed to enjoy it very much, but after a while, he became restless and moved around frequently, and finally became furious, pounding on the wall and hitting the door, like crazy...

70dB will interfere with conversations between people and affect work efficiency.

Living in a noise environment above 90dB for a long time will seriously affect hearing and cause neurasthenia, headache, high blood pressure and other diseases.

If suddenly exposed to a noise environment as high as 150dB, the eardrum will rupture and bleed, and both ears will lose their hearing completely.

The U.S. military tested a supersonic plane, and the plane flew over a chicken farm, rumbling...

As a result, more than 1 chickens died in the chicken farm in one day, and the sound of the aircraft engine was as high as 120dB~130dB, so many chickens were killed by the noise...

Therefore, in order to protect hearing, the sound should not exceed 90dB; in order to ensure work and study, the sound should not exceed 70dB; in order to ensure rest and sleep, the sound should not exceed 50dB.

Fang Yongzhi, who was sitting in the back, was dumbfounded. When he talked about this part of knowledge, he only read a few words in the textbook and asked the students to write them down, while Lin Feifei talked so much.

It is nothing more than to explain the impact of sound intensity levels on people's lives. Lin Feifan seems to be telling a wonderful story, which fascinates the students...

To Fang Yongzhi's surprise, next, Lin Feifei really told a story,
But this story is very common, a fairy tale that almost everyone has heard.

One night in summer, two little white rabbits were waiting for their mother at home. They waited for a long time, but their mother still didn't come back. They missed her so much.

At this time, there was a light knock on the door, and the little white rabbit sister was about to open the door, but the little white rabbit brother hurriedly stopped her and said, "I can't open the door, first ask who it is."

So, the little white rabbit sister said: "Who are you?"

The big bad wolf outside the door swallowed and said softly, "Open the door quickly, I'm grandma, and I'm bringing you delicious Chinese cabbage."

Brother Little White Rabbit said nervously after hearing the voice: "Sister, don't open the door, it's not grandma, it's a big bad wolf!"

……

(End of this chapter)