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| Practical Applications of Reflection of Sound |
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| Some applications of the principle of Reflection of Sound are: |
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| (1) Megaphone, (2) Hearing Board, (3) Sound Boards. |
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| (1) Megaphone: Megaphone is a horn-shaped tube. The sound waves are prevented from spreading out by successive reflections and are confined to the air in the tube. |
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| (2) Hearing aid: It is a device used by the people who are hard of hearing. Here the sound waves, which are received by the hearing aid are reflected into a narrower area leading to the ear. |
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| (3) Sound Boards: Curved surfaces can reflect sound waves. This reflection of sound waves is used in auditorium to spread the waves uniformly throughout the hall. Reflection of sound waves is done by using Sound Boards. The speaker is located at the focus of the sound board. |
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| A musical sound can be defined as a pleasant continuous and uniform sound produced by regular and periodic vibrations. |
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| Example: The pleasant sound produced by a guitar, piano, tuning fork etc. |
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| Noise can be defined as an irregular succession of disturbances, which are discordant and unpleasant to the ear. |
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| The sound heard after reflection from a rigid obstacle (such as cliff, wall) is called echo. |
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| The sensation of sound lasts or persists in our brain for 0.1 sec., even after the sources of sound has stopped vibrating. |
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| If d is the distance between the observer and the obstacle and V is the speed of sound, then the time taken by the sound to reach the obstacle and then to come back is calculated using the formula: |
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| or |
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| If velocity of sound is taken to be equal to 334 m/s and t = 0.1 sec, |
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| Thus, in order to hear the echo of a sound, the reflecting surface should be at a minimum distance of 17.2 m from the observer. |
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| Bats and dolphins can detect the presence of an obstacle by hearing the echo of the sound produced by them. This process is called sound ranging. |
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| One of the most important applications of the reflection of sound is oceanographic studies. For this purpose, we use a system called the SONAR. The SONAR is abbreviated form of Sound Navigation and Ranging. The SONAR system is used for detecting the presence of unseen under water object, such as submerged submarine, a sunken ship, iceberg and locating them. In Sonar ultrasonic waves are sent in all directions from the ship and are then received on their return after reflection. |
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| (1) It is used for medical diagnosis and therapy and also as a surgical tool. |
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| (2) Bats and porpoises use ultrasound for navigation and to locate food in darkness. |
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| (3) It is used to detect defective foetus. |
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| (4) It is used as a tool in the treatment of muscular pain. |
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| (5) Sonogram (is a technique of 3-dimensional photographs with the help of ultrasonic waves) is used to locate the exact position of an eye tumor. |
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