Why do we hear the sound of the sea when we put the shell to our ear? Well, let's start in order: no matter how similar this sound is to the sound of rolling waves, it is certainly not the sound of the sea.

But the question still remains: what exactly do we hear in the shell? In a word, it is noise; noise within us and external noise that we usually do not hear or pay no attention to because it is too quiet.

To amplify this noise, you need a resonator. The easiest one you can create yourself. Open your mouth in an “O” shape and tap your throat or cheek with your finger. You will hear a note. If you increase or decrease the "O" shape or change the shape of the mouth, then you will get different notes. In this case, your mouth acts as a Helmholtz resonator, in which sound is created by the air vibrating in a cavity with a single hole. By changing the shape of the resonating cavity, you can get different tones.

Perhaps at this point you are already thinking to close the article - after all, the question was about the sea and the shell, and not about some kind of Helmholtz resonator. But in reality, there is nothing complicated about it. The resonator is a spherical vessel with a hole in the neck. By acting on the resonator, we increase the pressure inside the cavity and force the air to “compress”. Then the air begins to "flow" back, and the pressure in the cavity drops, forcing the air to "flow inward" again. The resulting oscillations have a much larger amplitude than the oscillations of the acting field. The operation of the Helmholtz resonator is clearly shown in the video below.

It is interesting: Did you know that resonators are sold in huge quantities in regular grocery stores? It is enough to buy any bottle of water and, having freed it from the liquid, blow it perpendicular to its neck. Can you hear the hum? It is emitted by the vibrating air in the neck.

The same thing happens with a sea shell as with a Helmholtz resonator. The noise that we mentioned above, in the form of air moving inside and outside the shell, blood circulating in your head, talking in the next room - all this resonates inside the cavity of the shell, amplifies and becomes loud enough for us to hear it. Just as different mouth shapes create different tones, different shell sizes and shapes sound differently as different resonance chambers amplify different frequencies.

The fact that the sound of all the seashells is a bit like the sound of the sea is pure coincidence. If you bring any object that works on the principle of a Helmholtz resonator to your ear, you will hear a similar sound, regardless of whether this object is associated with the sea or not. Place an empty glass to your ear, or simply place your palm on it, leaving a cavity between its surface and your ear, and you will hear exactly the same sound.

Sink

If you put the mouth of a sea acorn shell or any other large shell to your ear, you can hear a distant rumble. The impression is that sea waves rise and break in the shell.

Therefore, sea shells are often brought home from the beach and taken to places far from the sea, as a living memory of it. Of course, it is very tempting to think about the surf, but it is not the sound of the sea that we hear in the sink. It is an echo and repeated echo of those sounds that enter the shell from the outside.

Echo and sink

Echoes are sound waves reflected from a smooth hard surface, which we hear as a repetition of some kind of noise.

If you enter the cave and shout loudly, then in a split second you will hear your own voice, which came back to you, reflected from the walls of the cave. Imagine sound waves as waves traveling across a wheat field on a windy day.

Interesting fact: the sounds entering the sink are repeatedly reflected by its walls.

Sound waves are also transmitted through the air, that is, sound is the vibrations of the air. When sound passes through the air, air molecules rhythmically contract and diverge, transmitting this process further. Rhythmically repetitive compression and rarefaction of air - these are sound vibrations.

But sound vibrations are transmitted not only by air. They also pass through other materials, such as wood. Stand in front of a closed wooden door and shout something loudly. First, your vocal cords will vibrate, transmitting these vibrations to the air. The air will transmit vibrations to the wood of the door. The vibrating door will make the air vibrate on the other side of the door. The vibrating air will reach your father's ears, who is standing outside the door. “Why are you shouting so loudly? Stop!" - he will say, and you, in turn, will also perfectly hear him.

But if you scream in a cave, then the material of the walls does not absorb sound, but reflects it back to you, in the same way the mirror reflects the light. True, instead of seeing your reflection, in this case you hear your voice. Sound-reflecting surfaces - ear mirrors. In Europe there are valleys surrounded by mountains that are famous for their echoes. A hunting horn signal can bounce off mountains about 100 times before it dies down.

The sound of the sea in the sink

The mention of multiple reflections of sound brings us back to the seashell. For listening to the so-called sea surf, the best shells are multi-chamber. These cameras are like a suite of rooms in an empty house. The walls of the sink are smooth and hard, so even faint sounds entering the sink are reflected and once again reflected from all the numerous walls. All external sounds - voices, music, slamming doors - merge into a rumbling noise in the sink.

Many of you have already come tanned from different shores - seas and oceans. And, of course, they brought a beautiful shell with them, so that at the moment of nostalgia for vacation, they could press it to their ear and hear the sound of the waves. And what does the shell really record on some invisible chips the sounds of the surrounding water element, and then all the time reproduces them inside itself?
Let's cut open the shell and look for recording devices there. As you understand, this idea is unlikely to be crowned with success, which means that it is not water that is making noise in the shell. What then? There is a theory that when we put a shell to our ear, we actually hear the sounds of blood flowing through our blood vessels. There are a lot of people who believe that this is really so. But this theory is refuted by one simple experiment: let's try to run a hundred meters at the fastest speed that we can, and then bring the shell to our ear. Our pulse increased, blood began to circulate at a faster rate, but the sound inside the shell did not change. This means that we do not hear the movement of our blood through the vessels at all.
The third theory is this: the shell makes noise due to the movement of air currents. This explains why the sound seems louder when the ear is brought closer to the shell, and quieter when it is farther. But this theory can be easily destroyed by coming with a sink to a soundproof room - we have such rooms on television. And what do we see? In a soundproof room, although there is air in it, the shell does not make the sound of the ocean. She is silent!
So, we easily got to the conclusion that the sounds of the sea can be heard only when there is noise around! This is the basis of the fourth, correct theory, which is based on the "Helmholtz resonance" - the author of classical works on acoustics. This is the same Hermann Ludwig Ferdinand Helmholtz, after whom our Research Institute for Major Diseases is named.
Back in 1850, Helmholtz understood why the phenomenon of air resonance in a cavity occurs, an example of which is the hum of an empty bottle from a stream of air directed perpendicular to its neck. Here is the formula for this resonance. You will say: but a shell is not a bottle. There is no neck there ?! It turns out inside - the shell consists of a whole chain of cavities with a narrow neck - a kind of suite of rooms. Ambient noise gets in and begins to resonate, hitting the walls of the shell. That is, we hear multiple echoes merged into solid noise. Therefore, the size and shape of the shell directly affects the noise emitted, the larger it is and the more curvatures, the richer the so-called noise of the sea will turn out.
And this is also easy to check. Place a glass or even folded palms to your ear. You will hear the same noise, albeit weaker.

Kalashnikov Mikhail

Purpose of work: to find out why the sound of the sea is heard in the shells

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MBOU SOSH №12 with in-depth study of individual subjects

Is there a sea in the shells?

MBOU SOSH №12

with in-depth study of individual subjects

Head: Korovina Tatiana Vasilievna

Surgut

1. Experimental part No. 1

Let's conduct an experiment: we bring various objects to the ear - samples.

Sample No. 1. Small shell

Sample No. 2. Large shell

Sample No. 3. Swirling shell

Sample No. 4. Cup

Sample No. 5. Palm

On the Internet, I read that the volume of the sound coming from the shell depends on its size and sinuosity.

Sample No. 1. The shell is small.

Putting the shell to my ear, I heard a faint, barely audible noise. It is very small, so there was almost no noise.

Sample No. 2. The shell is large.

This shell had more noise because it was much larger than the previous sample.

Sample No. 3. The shell is swirling.

The swirling shell turned out to be the loudest, because external sounds, reflected from the walls of the shell, turn into a rumble, similar to the sound of waves.

I wondered if other objects could make shell-like sounds?

Sample No. 4. Cup

It turns out they can. The noise of the glass is almost the same as in the second sample.

Sample No. 5. Palm

And the noise from the palm is quieter than from the glass. It is similar to the noise of a small shell, as the space in the palm is small and not twisted, meaning the sound is less reflected.

During the experiment, it turned out that the loudest sound comes from a large swirling shell.

1. Hypothesis number 2

On the Internet, I discovered one theory that we hear the sound of the movement of blood flowing through our blood vessels, which is reflected from the surface of the shell.

1. Experimental part No. 2

Let's conduct an experiment: we will do physical labor or just run for 5-10 minutes.Blood As you know, in such conditions it begins to circulate much faster, which means that the noise that we should hear will be much louder. In fact, its volume does not change at all.

1. Hypothesis number 3

Another hypothesis: this sound is formed due to the movement of air currents through the shell of the mollusc. Therefore, if the shell is kept at a short distance from the ear, then the noise seems much stronger than if the shell is brought directly to the ear.

1. Experimental part No. 3

Let's conduct an experiment: we will bring the shell to the ear and move it away from it. As a result of the experiment, it turned out that this theory has no basis either.

But if we carry out the same experiment in silence, in a soundproof room, then, despite the fact that there is air in the shell, the shell will not make noise and make sounds of the ocean.

So, it turned out that the sound of the sea turns out to be nothing more than the noise of our environment, which was reflected from the walls of the shell. Moreover, we hear it in a distorted form. And the larger the shell, the richer the sound is.

The noise inside the shell is also influenced by the ambient noise. The shell in its action is very similar to a resonator chamber. When external noise penetrates into the shell, reflecting against its walls, it is amplified. Therefore, the more noise outside, the louder the sound of the ocean (sea) seems.

1. Conclusions:

It turned out that

• the sound of the sea of ​​the shell turns out to be nothing more than the noise of the environment around us, which was reflected from the walls of the shell;
• we hear this sound in a distorted form;
• the larger and more sinuous the shell, the richer the sound is;
• the louder the sound of the environment, the louder the “sound of the sea”.

My hypothesis was confirmed - a shell that keeps the sound of the sea surf ... very romantic, but alas, this is a myth!

List of used literature

1. "GEOlenok" (GEOlenok). Monthly magazine, №1 / 2013, p. 28.
2. Do you know physics? / Ya.I. Perelman - M .: Tsentropoligraf, 2010.
3. Physics in games / B. Donat / Per. with him. - M .: Tsentropoligraf, 2011.
4. Scientific fun. Physics: experiments, tricks and entertainment: / Tom Tit - M .: Ast: Astrel, 2008.
5. http://qbici.ru/nauka/pochemu-v-rakushke-shumit-more/
6. http://class-fizika.narod.ru/9_26.htm
7. http://www.eduspb.com/node/1787
8. http://pochemu.su/pochemu-shumit-rakushka/

If you bring a clam shell to your ear, you can hear the sound of the ocean. No matter how far a person is from the ocean, he can always hear the rumbling waves rolling towards the shore. This noise is best heard in large, coiled strombids.

Many people believe that the sound we hear in the shell is just the sound of blood moving through the blood vessels of our ear. But that's not the point at all. If this were the case, then the sound would increase after exercise, when the blood begins to move faster. But even after playing sports, the sound does not change.

Others argue that this sound is generated by the movement of air currents through the shell of the mollusc. Therefore, if the shell is kept at a short distance from the ear, then the noise seems much stronger than if the shell is brought directly to the ear. But this theory has no foundation either. Because in a soundproof room, even though there is air in it, the shell does not want to play the desired melody of the ocean.

The theory that the noise of the ocean is produced by the noise of our environment seems to be the most true. The shell, if held at a distance from the ear, picks up this noise around us, which resonates inside the shell. The "sound of the ocean" is influenced by the size and shape of the shell. Because different shells pick up different frequencies. You can hear the sound of the ocean without shells. For example, you can pick up an empty glass or press your palm to your ear. Moreover, by moving a mug or hand, the sound of the "ocean" begins to change.

The noise inside the shell is also influenced by the ambient noise. The shell in its action is very similar to a resonator chamber. When external noise penetrates into the shell, reflecting against its walls, it is amplified. Therefore, the more noise outside, the louder the sound of the ocean appears.