Where is the echo?

Question 1: Which places are prone to echoes? Cave...in an empty house...mountain stream. Sound propagates in the form of waves, and waves will be reflected back when they encounter obstacles. The propagation speed of sound in the air is about 340m/s. Substitute into the formula: speed = distance/time 340=x/0.1 ==> x=34. Therefore, when the distance between the sound going and returning is greater than 34m, an echo will be generated

Question 2: Where is the echo valley when shouting?

Question 3: Where does the echo appear? If you shout in the valley, you will hear an echo. The echo wall in the Temple of Heaven in Beijing and the rumbling thunder on rainy days are echo phenomena. . We usually have echoes when we speak indoors, but the time it takes for the echo to reach the human ear is very short, and the human ear cannot distinguish the echo from the original sound. In this case, the echo is mixed with the original sound, making the original sound stronger. If the echo reaches the human ear more than 0.1s later than the original sound, the human ear can distinguish the echo from the original sound, and the echo can be used to measure the distance.

Question 4: Where can you hear the echo? If you shout in an empty classroom that is more than 17 meters long, you can hear the echo.

Question 5: Tell me where you heard it. Echo, what kind of physics does it feel like? Echo

During the propagation process, the sound wave will be reflected at the interface when it encounters a large reflecting surface (such as the wall of a building, etc.), and people can distinguish it from the original sound. The reflected sound wave is called an echo. The condition for the human ear to be able to distinguish the echo is that the reflected sound has sufficient sound intensity, and the time difference with the original sound must be greater than 0.1 seconds. When the size of the reflecting surface is much larger than the wavelength of the incident sound, the echo heard The clearest. That is, when the distance is 17 meters. As for the application of echo, sonar devices can be described as typical. Using echo to measure sea depth, the distance of icebergs and the orientation of enemy submarines are all completed by sonar devices with different functions. In 1912, The Titanic, a large British merchant ship, collided with an iceberg and sank on its way to the United States. This major shipwreck attracted worldwide attention. In order to find the sunken ship, American scientists designed and built the first instrument to measure underwater targets. An echo sounder is used to emit sound waves on the ship, and then the instrument is used to receive the sound wave signal reflected back from the obstacle. Measure the time between sending the signal and receiving the signal, and based on the speed of sound in the water, the distance to the obstacle and the distance of the sea can be calculated Depth. The first echo sounder successfully discovered an iceberg 3 kilometers away in 1914. In fact, this is the prototype of the sonar device that is now widely used in national defense and ocean development. During World War I, Germany The submarine sank a large number of warships and ships of the Allied Powers, and almost interrupted the maritime transportation lines across the Atlantic. At that time, the submarine was underwater, invisible and intangible, and was invincible for a while. Therefore, it became possible to use hydroacoustic equipment to search for submarines and mines. The key issue was solved. The famous French physicist Langevin and others studied and built the first active sonar. In 1918, they first received echoes from submarines 2 to 3 kilometers away in the Mediterranean Sea. This sonar can Various forms of acoustic signals are emitted in the water, and when they hit the target that needs to be located, a reflected echo is generated. After receiving it, the signal is analyzed and processed to remove interference, thereby displaying the target's orientation and distance. During World War II , because the war required more perfect sonar devices. After the war, people began to experiment with using the sound on warships to detect fish. Not only did they detect fish, but they were also able to distinguish the type and size of the fish. On this basis, people developed various Fish detection machines have greatly promoted the development of fisheries. Echo is also widely used in geological exploration. For example, in oil exploration, artificial seismic methods are often used, that is, explosive bags are buried on the ground and an array of probes are placed. By detonating explosives, the probe can receive the sound waves reflected from the interface between different underground layers, thereby detecting underground oil deposits. In terms of architecture, when designing and building large halls, the echo phenomenon must be considered as an important factor. In a closed After sound is generated in the space, the sound waves are continuously reflected on the four walls. Even after the sound source stops radiating, the sound will continue for a period of time. This phenomenon is called reverberation. If the reverberation time is too long, it will interfere with useful sounds. However, Too short reverberation is not good either, giving people a monotonous and unfulfilled feeling. Therefore, designers must take necessary measures, such as the internal shape, structure, sound absorption, sound insulation, etc. of the hall, to obtain the appropriate amount of reverberation. , improve indoor sound quality. 20Hz ~ 20000Hz, the range of human perception of sound. In addition, it is ultrasonic wave. It is infrasound wave. 0.38 ~ 0.72μm, the range of human perception of light. In addition, there are infrared rays and ultraviolet rays.

Question 6: Where else can I hear the echo? The empty house

Valley

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Question 7: Where is it? If you shout, there will be an echo. Where there are obstacles, the obstacles must be large enough and not too far apart.

For example, a valley or an empty room.

Hope you can adopt it.

Question 8: Under what circumstances will there be an echo? Where there are large reflecting surfaces, such as walls, mountains, etc.

Question 9: Where are the echoes likely to occur? In caves, empty houses, or mountain streams. Sound travels in the form of waves, and waves are reflected back when they encounter obstacles.

The propagation speed of sound in the air is about 340m/s. Substitute into the formula: speed = distance/time 340=x/0.1 ==> x=34. Therefore, when the distance between the sound going and returning is greater than 34m, an echo will be generated

Question 10: Where to shout Echo Valley