One wave
Every word you hear reaches your ear as one wiggle of air. Your ear splits that wiggle into low, middle, and high parts. This landscape does the same: time runs left to right, low to high runs front to back, and height is how strong each part is. Press play.
Two messages in one wave
Look along the front: thin, evenly spaced ridges climb and fall together. That is the buzz of the voice, and their spacing is the pitch. Further back, broad ranges rise and shift with every sound. That is the shape of the mouth. The buzz carries the tune. The mouth carries the word.
The instrument
Both messages come from one instrument. Air from the lungs sets how tall the landscape stands. The vocal folds buzz: that is the ridges and the pitch. Above them, the throat, mouth, and nose are a tube that rings, and the tongue, jaw, and lips change where. Narrow it to a slit and the air hisses. Tap a part to hear it and see what it moves.
Take away the tune
Here is the same sentence rebuilt twice: once on a single flat note, like a robot, and once whispered with no buzz at all. The tune is gone both times, and you can still understand every word.
Keep only the tune
Now the opposite. The hum keeps the sentence's exact pitch, loudness, and timing but closes the mouth. The hiss keeps only loudness and timing. Same tune, same rhythm, and the words are gone. In English, pitch shows feeling and emphasis. In Mandarin, it can change the word: hear four kinds of ma.
The mouth shapes the vowel
Drag the dot around the mouth map and watch the tongue, jaw, and lips move with it. The buzz stays on one note while the mouth bands move, and the vowel changes. Up and down is how open the jaw is. Left and right is how far forward the tongue sits. Change the pitch: same vowel. Shrink the speaker: the whole map shifts higher, which is how you can tell a child's voice.
Consonants are quick moves
Consonants live in fast changes, so this chapter draws each sound three times slower than it plays. A hiss that rings high sounds like /s/; ring it lower and it becomes /sh/. A pop of air with the voice right behind it is /b/. Make the voice wait about four hundredths of a second, the shaded gap, and the same pop becomes /p/.
How little is enough?
Here the sentence is cut into frequency bands, striped on the landscape, and rebuilt from noise that keeps only how loud each band gets. One band is nothing but loudness and timing. Most listeners start catching words around four bands; by 32 it sounds like a whisper, because noise has no pitch. Fill the same bands with the voice's own buzz and the speaker comes back. Three whistles that follow the mouth bands are enough too, once you know what to listen for.
Your turn
Turn on the microphone. Hold a long /ē/, slide to /ōō/, then open to /ŏ/, and watch the dot travel the mouth map while the drawing roughly follows your mouth. Whisper: the pitch line disappears and the mouth bands stay. Hum: the pitch stays and the bands flatten. Nothing you say leaves this device.
Words and music in reading
Reading aloud carries both messages. Accuracy and words correct per minute check the words. Expression checks the music: pitch, loudness, and timing. Practice the music in See Your Voice, the sounds in The Sound Table, and measure both with ReadingFluency.app.