PHY 8 Sound Flashcards

1
Q

What are sound waves ?

A

Longitudinal waves which can only be transmitted in a material, elastic medium.

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2
Q

What is the impact of a Vacuum on sound ?

A

Sound is produced by vibrating matter, there is no matter in a vacuum and therefore no sound.

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3
Q

What are compressions in terms of sound ?

A

They are also known as condensations - they are regions where particles of matter are close together.

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4
Q

What are rarefactions ?

A

Regions where particles are sparse. They are low pressure regions of sound waves.

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5
Q

What is the relative velocity of sound in solids, liquids and gases ?

A

Solids > Liquids > Gases

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6
Q

How does temperature affect the velocity of sound ?

A

Increase in temperature increases the velocity of sound.

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7
Q

What are frequencies below 20 Hz known as ?

A

Infrasonic

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8
Q

What are frequencies above 20 000 Hz known as ?

A

Ultrasonic

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9
Q

What is the sound frequency (pitch) that can be percieved by the ear ?

A

20 - 20 000 Hz

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10
Q

What are the SI units of Hertz ?

A

Cycles/Second = S-1

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11
Q

What is sound intensity ?

A

The rate of energy (power) propagation through space

intensity (I) = Power/Area = F2 x A2

F= Frequency, A = Amplitude

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12
Q

Describe a noise that could be heard at 160 DB ?

A

An aeroplane engine

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13
Q

Describe a sound that could be heard at 20 DB ?

A

A whisper

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14
Q

What are beats in terms of sound?

A

When sounds of different frequencies are heard together, they interfere. Constructive interference results in beats.

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15
Q
A
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