Voice Activity-5

Voice Activity-5

4th Grade Science Class Sound Activity Sound: These are simple vibrations that the ear can hear. People need to talk to communicate with each other and convey their feelings and thoughts. The basic element of speech is voice. Sound comes from a source. It spreads around like waves in water. We hear these sounds spreading around us with our ears. Sound propagates in liquids as well as in air. Some creatures living in the sea communicate in this way. But sound does not propagate in a vacuum. For example: no sound is heard in large explosions in space. Sound is a wave that occurs from the vibration of objects and moves from one place to another in the form of compression and expansion in a suitable medium (air, water, etc.). Therefore, sound is a pressure wave. The propagation speed of sound is 340 m/sec in air at 20o C. The speed of sound is affected by the temperature of the environment. As the temperature increases, the speed of sound also increases. Increasing temperature increases the vibration speed of molecules, thus causing the propagation speed of sound to increase. When sound waves encounter obstacles while traveling, they undergo reflection. In reflection, the speed of sound does not change, but its direction changes. The reflection of sound has made it easier for some creatures. For example; Bats determine their direction of movement by using the reflection of the sounds they make on objects. When the sound coming from the sound source is reflected back and heard again after hitting the obstacle, it is called echo.

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