17.2 声音速度
章节大纲
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Has this ever happened to you? You see a flash of lightning on the horizon, but several seconds pass before you hear the rumble of thunder. The reason? The speed of light is much faster than the of sound.
::这是否发生在你身上?你看见地平线上有闪电,但数秒后你才听到雷声响起。原因?光速比声音快得多。What Is the Speed of Sound?
::声音的速度是什么?The speed of sound is the that travel in a given amount of time. You’ll often see the speed of sound given as 343 meters per second. But that’s just the speed of sound under a certain set of conditions, specifically, through dry air at 20 °C. The speed of sound may be very different through other matter or at other temperatures.
::声音的速度就是在一定时间内的飞行速度。 你通常会看到声音的速度为每秒343米。 但这只是在一定条件下的声音速度,具体来说,就是在20°C的干燥空气中。 声音的速度可能因其他物质或其他温度而有很大不同。Speed of Sound in Different Media
::不同媒体声音速度Sound waves are mechanical waves, and mechanical waves can only travel through matter. The matter through which the waves travel is called the medium (plural, media). The Table gives an approximate speed of sound for several different media. Generally, sound waves travel most quickly through solids, followed by , and then by . Particles of matter are closest together in solids and farthest apart in gases. When particles are closer together, they can more quickly pass the of vibrations to nearby particles.
::声波是机械波,机械波只能穿梭于物质中。波浪穿行的事物被称为介质(多面、介质 ) 。 表格给出了几种不同介质的近似声音速度。 一般而言,声波最迅速地穿行于固体中,随后是,然后是。 物质粒子在固体中最接近,气体中最接近。 当粒子相近时,它们可以更快地将振动传递到附近的粒子中。Medium (20 °C) Speed of Sound Waves (m/s) Dry Air 343 Water 1481 Hard Wood 3960 Glass 4540 Aluminum 6320 Q: The table gives the speed of sound in dry air. Do you think that sound travels more or less quickly through air that contains water vapor? (Hint: Compare the speed of sound in water and air in the table.)
::问题:表格给出了干燥空气中声音的速度。您认为声音在含有水蒸气的空气中移动的快或快吗? (提示:比较表中的水和空气中声音的速度。 )A: Sound travels at a higher speed through water than air, so it travels more quickly through air that contains water vapor than it does through dry air.
::A:声音在水中以比空气更快的速度流过水中,因此它通过空气中含有水蒸气的速度比通过干空气的速度要快。Temperature and Speed of Sound
::声音的温度和速度The speed of sound also depends on the of the medium. For a given medium, sound has a slower speed at lower temperatures. You can compare the speed of sound in dry air at different temperatures in the following Table . At a lower temperature, particles of the medium are moving more slowly, so it takes them longer to transfer the energy of the sound waves.
::声音的速度也取决于介质的速度。对于给定的介质,声音在较低温度下的速度较慢。您可以在下表的不同温度下比较干燥空气中声音的速度。在较低温度下,介质的粒子移动较慢,因此它们转移声波的能量需要更长的时间。Temperature of Air Speed of Sound Waves (m/s) 0 °C 331 20 °C 343 100 °C 387 Q: What do you think the speed of sound might be in dry air at a temperature of -20 °C?
::问题:你认为在 -20°C的温度下, 声音的速度在干燥空气中会是多少?A: For each 1 degree Celsius that temperature decreases, the speed of sound decreases by 0.6 m/s. So sound travels through dry, -20 °C air at a speed of 319 m/s.
::A:每摄氏1摄氏度温度下降,声音速度下降0.6米/秒。所以声音以319米/秒的速度穿过干、20°C空气。Can you calculate the speed of sound in air and the on the string in the Violin simulation below? Use the vs Frequency graph on the top left to analyze the waves produced by the violin. The product of the wavelength and frequency can be used to determine the speed of sound in air and wave speed on the violin string:
::您可以在下面的 Violin 模拟中计算声音在空气中和弦上的速度吗? 使用左上方的 vs 频率图分析小提琴产生的波。 波长和频度的产物可以用来确定小提琴弦中音速和波速的速度:Summary
::摘要-
The speed of sound is the distance that sound waves travel in a given amount of time. The speed of sound in dry air at 20 °C is 343 meters per second.
::声音的速度是声波在一定时间内行走的距离。 20 °C 的干空声音速度是每秒343米。 -
Generally, sound waves travel most quickly through solids, followed by liquids, and then by gases.
::一般来说,声波在固体中流动最快,其次是液体,然后是气体。 -
For a given medium, sound waves travel more slowly at lower temperatures.
::对于某一介质而言,声波在低温下行走较慢。
Review
::回顾-
What is the speed of sound in dry air at 20 °C?
::20°C时干燥空气中声音的速度是多少? -
Describe variation in the speed of sound through various media.
::说明通过各种媒体声音速度的变化。 -
Explain how temperature affects the speed of sound.
::解释一下温度如何影响声音的速度。
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The speed of sound is the distance that sound waves travel in a given amount of time. The speed of sound in dry air at 20 °C is 343 meters per second.
