🎼 音调：声音的高低由频率说了算🎼 Pitch: frequency sets how high a sound is
上一片弄清了声波——空气一疏一密地传过来。可蚊子嗡嗡是尖的，老牛哞哞是沉的，同样是声音，高低差别从哪来？这一片就管这件事：音调。Last leaf we met the sound wave — air passing along in pushes and pulls. Yet a mosquito buzzes high and an ox moos low. Same kind of thing, so where does the difference come from? This leaf is all about pitch.
第 1 步：一只蚊子，一头老牛Step 1: One mosquito, one ox
先看一对反差最大的嗓子。Start with the most extreme pair of voices around.
蚊子翅膀每秒振动约 600 次，声音又尖又细；老牛的叫声每秒约 100 次，低沉浑厚。每秒振动的次数叫频率（frequency），单位是赫兹（Hz）：600 次/秒 = 600 Hz。频率高，音调就高——所以音调说的不是“声音大小”，而是声音的高低。A mosquito's wings flap about 600 times a second — a high, thin sound. An ox's moo is about 100 times a second — deep and low. The number of vibrations per second is the frequency, measured in hertz (Hz): 600 per second = 600 Hz. High frequency, high pitch. Pitch is not about loudness at all — it is how high or low a sound sits.
那频率又由什么决定？看看吉他手每天琢磨的东西。So what sets the frequency? Look at what guitarists fuss over every day.
第 2 步：弦越细、越紧，音越高Step 2: Thinner and tighter means higher
同一根弦，越细、绷得越紧、按得越短，振动就越快，频率越高、音调越高；换成粗弦或把弦拧松，振动变慢，声音就低。吉他手拧旋钮“调音”，调的就是弦的松紧——也就是频率。弦乐器、管乐器、鼓，所有乐器调音都是这个道理。On the same string: thinner, tighter, or shorter makes it vibrate faster — higher frequency, higher pitch. A thicker string, or one you loosen, vibrates slowly and sounds low. When a guitarist turns the tuning pegs, they are changing the string's tension — that is, its frequency. Every instrument, from strings to pipes to drums, is tuned the same way.
把声音画成波形，频率的差别一眼就能看出来。Draw sounds as waves, and the frequency difference jumps out at you.
第 3 步：波形越密，音调越高Step 3: Denser waves, higher pitch
频率低的音，波形稀稀拉拉；频率高的音，波形又密又挤。人耳能听到的范围是 20 ~ 20000 Hz：低于 20 Hz 叫次声波，高于 20000 Hz 叫超声波，我们都听不见——蝙蝠和海豚却能用超声波“看”清世界。你能听到的最高音，还会随年龄慢慢下降哦。A low note draws a sparse, lazy wave; a high note packs the wiggles tight. Human ears catch roughly 20–20000 Hz. Below 20 Hz is infrasound, above 20000 Hz is ultrasound — we hear neither, but bats and dolphins use ultrasound to “see”. And the highest note you can hear slowly drops as you grow up.
🎮 你来当调音师（30 秒）🎮 Your turn: run the frequency generator (30 seconds)
道理讲完了。拖动频率滑块，看波形由疏变密、音高尺的指针往右跑；点“🔊 听一听”用耳朵验证，再接下 4 关挑战。Theory done. Drag the frequency slider and watch the wave go from sparse to dense as the pitch needle slides right; hit “🔊 Listen” to check with your ears — then take the 4 challenges.
一句话记住它：音调是声音的高低，由频率（每秒振动次数）决定——频率越高，音调越高。Remember it in one line: pitch is how high or low a sound is, set by frequency (vibrations per second) — higher frequency, higher pitch.
频率单位赫兹（Hz）= 每秒振动次数；蚊子约 600 Hz，老牛约 100 HzFrequency in hertz (Hz) = vibrations per second; mosquito ≈ 600 Hz, ox ≈ 100 Hz频率越高 → 波形越密 → 音调越高Higher frequency → denser wave → higher pitch弦越细、越紧、越短，频率越高；调音就是调松紧Thinner, tighter, shorter strings sound higher; tuning means changing tension人耳范围 20 ~ 20000 Hz，次声、超声都听不见Human hearing spans 20–20000 Hz; infrasound and ultrasound are out of reach
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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