What is the acoustic knowledge of Sound in Snow Falling into the Water?

When it rains, we can always hear voices, from small to large, pouring down, scratching. But what about snow? Have the students ever heard the sound of snow? Yes, snowflakes fall into the water quietly, which sounds silent to us. However, snowflakes still emit sound waves when they fall into the water. First of all, the frequency of sound waves emitted by snowflakes falling into the water is between 50 kHz and 200 kHz, and whales in the sea can hear the sound produced by snowflakes falling into the water, which makes whales extremely uneasy. However, please don't take it for granted that these sounds are made by snowflakes hitting the water. Where did they come from? Let's look at a story first, from which we can grasp the principles of physics. The story happened during the Cold War. At that time, the US Navy wanted to monitor the activities of Soviet submarines. They found that underwater sonar is not effective when it rains, and it is often disturbed by noise, and even can't be monitored.

They handed this question to Professor kramer of the Acoustic Physics Laboratory of the University of Washington, and kramer found Professor Pross Pelletti, who is quite famous in the field of acoustics and a wizard. Prost Pelletti suspected that these sounds should not be made by raindrops hitting the water surface, but the vibration of bubbles contained in raindrops. He told the idea to other scientists, and most of them shook their heads. However, Cramer has a device that these scientists don't have: a high-speed underwater camera that can take 1000 photos per second. Using this camera, he did find bubbles in the water when it rained, and these bubbles were still shrinking, expanding and vibrating. He also found that the vibration of large bubbles produces low-frequency sound waves, while the vibration of small bubbles produces high-frequency sound waves. Others told them that fishermen often complain that when it snows, sonar often can't hear the activities of fish. They didn't believe it at first, because snowflakes contain more than 90% water and there is not much air. Later, on a snowy night, they found evidence in a motel swimming pool. When snowflakes fall into water, they also produce bubbles. Similarly, these bubbles vibrate, thus generating sound waves. In fact, neither the subtle sound people hear when splashing water nor the rumble of waterfalls comes from the collision between rocks and water, but from bubbles.

Fishermen often complain that falling snow can't detect fish, so will the fish be affected? Do fish have ears? Can they hear voices? The answer is that fish do have ears, and most fish have good hearing.

There is a tympanic membrane in the human ear. When sound enters the ear, the eardrum vibrates. When this vibration reaches the auditory part in the ear, sound can be heard.

Sound travels much easier in water than in air. There is a lot of water in the fish's body, because the fish has no eardrum, and the sound reaches the ears directly through the fish's body. In fact, most fish's ears are not connected to the outside world at all, but are protected in bags on both sides of their heads, that is, behind their eyes.

Many kinds of fish can collect sounds in another way. Their ears are connected to the swim bladder, and the sound in the water makes the swim bladder wall vibrate, just like the eardrum vibrates through the sound of air. Then, this vibration is usually transmitted to the ear along a series of small bones connected to the swim bladder. Some fish do not transmit vibration through small bones, but through tubular organs extending from the swim bladder.

Sound is very important to fish. Many fish can make powerful calls to each other and can be heard thousands of meters away. Some fish make sounds by grinding their teeth, and some fish make sounds by rubbing their fins on their bodies. Many fish use the swim bladder to distinguish sounds. Special percussion muscles vibrate the swim bladder to make a sound.