How to eliminate resonance phenomena and how to avoid resonances

During the Tang Dynasty, a strange thing happened in a monastery in Luoyang. There is a bronze chime in the room of the temple, and no one knocks on it, but it often "buzzes" by itself, what is the reason here?

It turns out that this chime and the big bell in the canteen are exactly the same number of vibrations per second when they make sounds. Whenever the little monk rings the bell, the vibration of the bell makes the surrounding air vibrate with it, and when the sound wave reaches the chime in the old monk's room, because the frequency of the chime is the same as the frequency of the sound wave, the chime also vibrates. There was a "buzzing" sound.

This is the phenomenon of resonance in which vibrations occur, also known as resonance.

You have noticed, the lower end of the huqin has a small "belly" - a bamboo tube covered with snakeskin. When you play the huqin with great interest, the vibration of the strings through the snakeskin will cause the resonance of the air in the "belly", so that the sound of the piano is not only loud, but also plump, melodious and beautiful. People call this "belly" the resonance box.

You see, don't all musical instruments such as dulcimer, pipa, violin, and piano have resonance boxes of various shapes and sizes?

In addition to the resonance box, there are many other good things that people use the resonance phenomenon to do.

When building a house, whether it is pouring concrete walls or floors, in order to improve the quality, they always pour concrete on one side and use an oscillator on the other side, so that the concrete is tighter and stronger due to oscillation.

Pedestrians on the streets, the noise of vehicles, the rumbling of machines – these constant noises not only affect people's normal lives, but also damage people's hearing. There is a resonant muffler that consists of an orifice plate and cavity with many small holes. When the frequency of the noise is the same as the natural frequency of the resonator, it will resonate violently with the air column in the hole.

In this way, the sound can be converted into heat energy when it resonates, so that a considerable part of the noise is "swallowed".

In addition, pulverizers, vibrometers, electric vibration pumps, etc., also use the resonance phenomenon to work.

But in some cases, the phenomenon of resonance can also be harmful. For example, when an army crosses a bridge, the orderly pace can create vibrations.

If its frequency is close to the natural frequency of the bridge, it may resonate the bridge to the point of breaking. Therefore, the troops had to take a quick step to cross the bridge.

In the northwest of our country, the mountains are covered with snow all year round. When the spring flowers bloom and the snow melts on the mountain, the snow layer will slide away from its original place. Often, an occasional roar will cause the thick layer of snow to collapse due to resonance, so it is stipulated that the survey team members who climb the snow-capped mountains and the mountaineers cannot speak loudly.

We need to make full use of resonance in all scientific fields, and we must also prevent resonance from harming our lives, work, and the environment. This requires us to continue to study and explore.

The easiest way: if the water pipe is iron, grind one of them, so that it changes the common frequency between them, only when the frequency is the same, there will be resonance, if it is plastic, there should not be too much sound? If you think it's noisy, you can fix him, it should work, you give it a try!

I think that the water pipe should be tied to a different weight, so that the weight changes, and the frequency of the weight must be different from the water pipe. If the difference is large, the resonance phenomenon will be reduced.

Residents have no choice. This is generally caused by the insufficient power of the water pump. My family used to be like this, and then the property replaced the water pump.

Immobilize him, or take steps to change his frequency.

Change the natural frequency of an object.

Air vibration: In general, the air travels slowly and decreases rapidly. Therefore, in order to prevent air vibrations, we try to make our spaces as large as possible.

And the material with a large difference in the fixed frequency should be selected in the space. In this way, the resonance frequency can be staggered, and the space objects can be avoided from resonating at the same time, forming a resonance trough.

Put more bonsai on the balcony and in the room, preferably leafy bonsai. This will also absorb a certain frequency, reduce room resonance, and renovate the room layout through renovation, change the glass door or glass partition wall, or redecorate. Improve room resonance at the root.

Resonance phenomenon. An object or a system is inclined to vibrate at a certain frequency without the influence of an external force, which is the "natural frequency". When the natural frequencies of two objects are the same or similar, their vibrational amplitudes will be superimposed, that is, they will produce an amplification effect, which will force the glass to vibrate violently and eventually shatter.

The power of resonance should not be underestimated, speaking of which, it has to be mentioned that the abnormal shaking incident of the Humen Bridge that occurred on May 5, 2020 is very similar to it, although the harm of resonance is indeed great, but it is also cleverly used in all aspects of life, the magic of the instrument, the playing of the Xuan instrument, the gorgeous laser beam, the electromagnetic waves of the universe, etc., are inseparable from the excellent performance of the principle of resonance.

First of all, it is much easier to understand the mechanism of resonance, so that it is much easier to solve the problem. In order to make the frequency of the external force different from the intrinsic frequency of the object, it is necessary to consider what determines the frequency of the object. For example, circular motion, or a car or train crossing a bridge, will limit the speed so that the frequency of the external force is different from the intrinsic frequency of the object.

It depends on the occasion. If it is a car glass resonance, it can change the speed of the vehicle or change the size of the car parts, of course, the feasibility should be considered. If the sound causes resonance, the frequency of the sound can be changed or the size of the vibrating object can be changed.

In short, theoretically, it is necessary to change the vibration frequency of the vibration source, or change the geometric size and shape of the vibrating object, thereby changing its own natural resonant frequency.

Make the vibration frequency as far as possible from the natural frequency of the object.

It's hard to resonate in reality, so don't worry.

The phenomenon of resonance refers to the phenomenon that when an object or system is subjected to external vibration, the vibration frequency of itself is close to the external vibration frequency, and the amplitude will increase significantly. To put it simply, resonance is a phenomenon of energy transfer, when an object matches the frequency of the applied vibrational source with the frequency of the vibrational source, it can absorb more energy and produce a greater amplitude.

The phenomenon of resonance is widely used in many fields, such as mechanics, electronics, and other fields. In the field of machinery, resonance can be used to enhance the vibration amplitude of mechanical systems; In the field of electronics, resonance can be used to select specific frequencies, such as tuning circuits in electronic devices such as televisions and radios.

However, the resonance phenomenon may also lead to the loss of control and damage of the system, such as bridges, caves and halls buildings and other structures will be out of control and damaged under the action of too high frequency, so it is necessary to consider the factors of resonance in the design to avoid the risk of resonance out of control.

1.A curtain can be installed behind the door between the room and the balcony, and the fabric is preferably a thicker cotton cloth that can absorb a certain frequency.

2.Put more bonsai on the balcony and in the room, preferably leafy bonsai. This will also absorb a certain frequency, reducing room resonances.

3.Renovate the room layout, remove glass doors or glass partition walls, or redecorate. Improve room resonance at the root.

4.You can add a piece of sound-absorbing material to the doors and windows. The most used sound-absorbing materials are cotton, wool, linen, and styrofoam. These porous materials attenuate the vibrations of sound waves.

5.In the same case, sound-absorbing materials such as cotton, wool, linen, and foam can also be used on doors and windows. These porous materials attenuate the vibrations of sound waves.

This is a big problem. We can dampen the vibration of the vibration. From effectively reducing resonance noise and eliminating resonance phenomena.

Experts say that during MR scanning, especially superconducting systems, there is sometimes a strong noise, causing discomfort and even fear for patients. If the subject is nervous and moves, it will affect the effect of the image. Professor Mansfield (2003 Nobel Prize in Biomedicine) once said that the most prominent shortcoming of MR is that it is too noisy.

So where does the sound noise of magnetic resonance come about?

MR sound noise is mainly related to the switching of gradient fields. The magnetic field used in magnetic resonance imaging mainly includes two components, one is the main magnetic field, which is uniformly distributed in space and is the basic condition for generating magnetic resonance signals. The second is the gradient field, which varies in intensity with different spatial positions, and is used to locate the positions of different human tissues.

The main magnetic field is generated by a permanent magnet or superconducting coil and does not change over time. The gradient field is generated by a gradient coil and varies over time during the sweep. Force on Gradient CoilIn general, the gradient coil is located in the main magnetic field, and due to the current in the coil, according to the left-handed law of fleming, the wire in the coil is affected by the Lorentz force.

Generally speaking, scans such as epi that require fast switching of gradient fields in the same system produce more noise than other scans. Depending on the system, the stronger the gradient field, the better the switching performance and the louder the noise. There are two main diffusion paths for the diffusion of noise sources, one is air propagation and the other is solid contact diffusion.

The noise is diffused by the gradient coil through these two diffusion methods, either directly to the ear of the patient being examined, or it causes other components to vibrate, generating a new source of noise, and then transmitting it to the human ear.

This is an equipment problem that should not be avoided at present, and the practice of well-known hospitals now is only to cover their ears.

The main magnetic field, evenly distributed in space, is the basic condition for the generation of magnetic resonance signals.

2.Gradient fields, which vary in intensity with different spatial positions, are used to locate the position of different human tissues. The main magnetic field is generated by a permanent magnet or superconducting coil