Question

II. Answer the following questions
1. When does an object produce sound?
2. What is the frequency of a sound wave?
3. What kind of sound waves produce a pleasant sound?
4. What is an echo?
5. How do bats fly safely in darkness?
6. What are wind instruments?
7. What causes sound pollution?
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Answer 1

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• Sound is produced when materials vibrate. Energy in sound waves can be transmitted from one substance to another. The air molecules are pressed together when the vibrating object moves forward and pushes against them.
• Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure, the corresponding wavelengths of sound waves range from 17 m (56 ft) to 17 mm (0.67 in).
• Noise and musical sound (pleasant sound) , both are the mixtures of sounds of different frequencies but frequencies in musical sound are discrete and rational and wave pattern is periodic and regular but noise frequencies are continuous and irregular . So music is an pleasant sound produced by regular wave patterns .
• A sound that is repeated as it is sent back off a surface such as the wall of a tunnel.
• Bats fly safely in darkness because these have fine sense of locating echoes. They produce high pitched sounds. The sound bounce off the objects they hit and return to them as an echo. Echo location helps bats to locate objects in darkness and fly safely at night.
• A wind instrument is a musical instrument that contains some type of resonator (usually a tube) in which a column of air is set into vibration by the player blowing into (or over) a mouthpiece set at or near the end of the resonator.
• The source of outdoor noise worldwide is mainly caused by machines, transport, and propagation systems. Poor urban planning may give rise to noise disintegration or pollution, side-by-side industrial and residential buildings can result in noise pollution in the residential areas.

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Answer 2

Answer:

1. Sound is produced when materials vibrate. Energy in sound waves can be transmitted from one substance to another. The air molecules are pressed together when the vibrating object moves forward and pushes against them.

2. Sound that is perceptible by humans has frequencies from about 20Hz to 20,000Hz. In air at standard temperature and pressure,the corresponding wavelengths of sound waves range from 17m(56ft) to 17mm(0.67in).

3. Noise and musical sound (pleasant sound), both are the mixtures of sound of different frequencies but frequencies in musical sound are discrete and rational and wave patterns is periodic and regular but noise frequencies are continuous and irregular. So music is an pleasant sound produce by regular wave patterns.

4. A sound that is repeated as it is sent back off a surface such as the wall of a tunnel.

5. Bats fly safely in darkness because these have a fine sense of locating echoes. They produce high pitched sounds. The sound bounce off the object they hit and returns to them as an echo.Echo location helps bats to locate objects in darkness and fly safely at night.

6. A musical instrument that you play by blowing through it is known as wind instrument.

7. The source of outdoor noise worldwide is mainly caused by machines, transport, and propagation systems. Poor urban planning may give rise to noise disintegration or polluted,side-by-side industrial and residential buildings can result in noise pollution in the residential areas.

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