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How does sound relate to energy? |
Sound waves transport energy from one place to another. |
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What is the relationship between frequency and pitch? |
Pitch is the human perception of sound frequency. |
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What is the average range of a young person’s hearing? |
20 to 20,000 hertz |
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Distinguish between infrasonic and ultrasonic sound waves. |
Infrasonic is too low in frequency (below 20 Hz) for humans to hear, whereas ultrasonic is too high (above 20,000 Hz). |
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Relative to solids and liquids, how does air rank as a conductor of sound? |
Relative to solids and liquids, air is a poor conductor of sound. |
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Why won’t sound travel in a vacuum? |
There is no material in a vacuum to vibrate and carry the sound. |
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Distinguish between a compression and a rarefaction. |
In a compression, the molecules are closer together than average; in a rarefaction, they are further apart. |
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Do compressions and rarefactions travel in the same direction, or in opposite directions, in a wave. |
They travel in the same direction at the same speed. |
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What factors does the speed of sound depend upon? What are some factors that it does not depend upon? |
It depends on temperature and humidity, not on loudness and frequency |
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What is the speed of sound in dry air at 20°C? |
340 m/s |
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Does sound travel faster in warm air or in cold air? In humid air or dry air? |
Faster in warm air, faster in humid air |
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Which is normally greater, the energy in ordinary sound or the energy in ordinary light? How does the speed of sound compare to the speed of light? |
The energy in ordinary light is greater than the energy in ordinary sound. The speed of sound is a million times less than the speed of light. |
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What ultimately happens to the energy of sound in the air? |
It becomes thermal energy. |
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The pitch of sound is most closely related to _________. |
frequency |
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What is an echo? |
Reflection of sound is an echo. |
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What is a reverberation? |
A sound that persists after many reflections |
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Sound travels from one place to another mainly in a series of _________. |
compressions and rarefactions |
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What is the difference in the speed of sound on a warm day versus on a cold day? |
It is faster on a warm day and slower on a cold day. |
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Why did the campers in Dr. Hewitt’s story hear the sound of the campers across the lake more clearly at night than during the day? |
The temperature change from cold at the surface to warm at the top changed the shape of the sound waves. |
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How does the direction of sound travel compare to the shapes of the sound waves? |
The sound is at right angles to the waves. |
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How does the cooler air above the lake affect the movement of sound at night? |
Because it is colder just above the surface and warmer higher above, the sound wave is refracted toward the ground. |
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How do the waves of sound travel on the night that produces the temperature inversion, and why? |
The waves bend toward the ground because it is warmer above and colder lower below, and waves travel more slowly through the colder air. |
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What is the cause of refraction? |
Different speeds of sound in a medium |
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Does sound tend to bend upward or downward when its speed is less near the ground? |
Downward |
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Why does sound sometimes refract under water? |
Changing temperature changes the speed of sound in water. |
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What is ultrasound? |
Sound above the frequency of human hearing |
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Why will a struck tuning fork sound louder when it is held against a table? |
The table is forced to vibrate, and its large surface vibrates more air than the tuning fork. |
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Which two factors determine the natural frequency of an object? |
Elasticity and shape |
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The speed of sound in air varies with _________. |
air temperature |
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How do forced vibrations relate to resonance? |
When forced vibrations match an object’s natural frequency, resonant amplification occurs. |
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When you listen to a radio, why do you hear only one station at a time rather than all stations at once? |
The natural frequency of the electronics is tuned to resonate with the frequency of one station. |
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How did wind-generated resonance affect the Tacoma Narrows Bridge in the state of Washington in 1940? |
The resonant amplification of bridge motion destroyed the bridge. |
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A reverberation occurs when sound undergoes _________. |
multiple echoes |
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Refraction of sound occurs with changes in wave _________. |
speed |
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What physical phenomenon underlies the production of beats? |
interference |
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What beat frequency will occur when a 370-Hz and a 374-Hz sound source are sounded together? |
4 Hz |
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How does a radio wave differ from a sound wave? |
A radio wave is an electromagnetic wave that travels at the speed of light, whereas a sound wave travels at the speed of sound through air or another elastic medium. |
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Forced vibrations mainly occur in _________. |
sounding boards |
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The natural frequency of a small bell is _________. |
higher than for a larger bell |
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Resonance occurs when forced vibration _________. |
matches natural frequency |
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Interference is a property of _________. |
sound, light, and water waves |
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The phenomenon of beats is most closely related to _________. |
interference |
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