The Language of Sound, Season Three: the science of sound

Watch the season opener: Air That Moves. Then The Harmonic Series. Licensed CC BY 4.0. Seasons One and Two are on the playlist, and every episode of every season is on The Language of Sound and Films.

The idea

Season One was the language of music. Season Two went inside the synthesizer, one way of making a voice per episode. Season Three goes underneath both. Before the tuning and the machines there is the physics: air, pressure, the harmonic series, beats, resonance, the ear.

Each season gets its own look. This one is called Open Air. The background is no longer a lab graticule or an engine room. It's a lattice of air molecules, and a pressure wave travels through it the whole time. Coral where the air bunches up. Periwinkle where it spreads out. In the opening the lesson's own clicks drive it. Everywhere else the music does.

The sound has a rule too. Every Season Three score grows out of the thing the episode teaches.

Episode one: Air That Moves

Watch Air That Moves.

Push the air once and you get a click. Push it again, and again. Faster, and somewhere past twenty or thirty pushes a second the clicks stop being clicks. They blur into one tone. How often the air is pushed is the pitch. A hundred and ten a second is an A. Twice as often and the pitch jumps an octave. Twice again, another.

Now push harder instead of faster. The pitch stays put. The note just gets louder. How often is pitch. How hard is loudness.

The air itself barely moves. Each molecule nudges the next and the push races on, about 343 meters a second. In 1660 Robert Boyle pumped the air out of a glass jar with a ticking watch inside. As the air went, so did the ticking.

The breakdown is the other half. Two identical waves, crest on crest, add up and the swing doubles. Slide one by half a cycle, crest on trough, and they cancel. The music goes to true digital silence for about three seconds. Noise-cancelling headphones do exactly this.

The score is built from one thing: a single pressure pulse. The opening plays the lesson live. Three clicks on the spoken words. A train of them speeding up until it fuses into 110 Hz. Exact octaves. Four steps, each exactly six decibels louder, at the same pitch. Then the tone slows back into clicks, and the last click is the song's first kick. From there it's deep progressive house in A minor where the kit is the pulse too: the kick is a falling run of pushes, the hats are single pushes, the clap is four. Every hook starts as a click train that speeds up until it becomes a note.

Episode two: The Harmonic Series

Watch The Harmonic Series.

A flute and a violin play the same note. Same pitch. So why can you tell them apart? The answer is inside the note itself.

A string is pinned at both ends, so it can only swing in shapes that fit between them: the whole length, two halves, three thirds. It swings in all of them at once. The shorter shapes swing faster. Halves go twice as fast, the same note an octave higher. Thirds go three times as fast, a fifth above that octave. Then four times, five, six, every whole number, stacked on top. You don't hear sixteen notes. You hear one note getting richer. That stack is the harmonic series. Season Two's Additive built a voice out of these same sines, one at a time; this is the physics underneath it. In 1701 the French scientist Joseph Sauveur gave the parts their names: the lowest is the fundamental, everything above it a harmonic.

The flute and the violin play the same stack. What changes is the mix. A flute is mostly the bottom few harmonics, a violin stays bright far up the stack, and that mix is the color of a sound, its timbre. Harmony starts here too. Harmonics four, five and six are A, C sharp and E, a major chord already hiding inside one note. A bugle has no valves, so every call it can play is one of these steps.

Then the trick. Take the fundamental away and the pitch doesn't move. Everything left is still spaced the same distance apart, so the wave still repeats at the same rate, and the brain fills in the note that isn't there. Take the second and third harmonics away as well and it's still the same note. That's how a deep voice stays deep on a tiny phone speaker that can't play its lowest notes.

The score is cathedral trance on a pipe organ, because an organ's stops are tuned to the harmonic series: the 8 foot stop is the fundamental, the 4 foot the octave, and on up. The lesson is played live, one A built from exact sine waves, each harmonic entering on the word that names it, so the seventh really is a little flat, a note no piano has. The first build pulls the stops on the words. The first drop plays one hook through four registrations, flute, reed, hollow odd harmonics and full organ, so the color is what develops. The breakdown takes the fundamental away for real, then the band comes back through a tiny speaker with nothing in the low end, playing a bass line whose fundamentals are never there. The second drop is that idea as music: it hits through the speaker, then the low end slams back in. Every melodic note is a harmonic of A.

Season Three

1. Air That Moves, sound is pressure moving through air.
2. The Harmonic Series, every note is a stack of whole-number multiples.
3. Beats, two close pitches throb at their difference.
4. Resonance, things sing at their own frequencies.
5. The Ear's Curve, loudness is not level.
6. Rough and Smooth, why some intervals clash.
7. Where Is It?, how two ears find a sound.
8. Illusions, the sounds the brain invents.

How it is made

Python, PIL and FFmpeg on a laptop. No GPU, no subscriptions. The music is ChipForge, an offline numpy synthesizer, and every visual reads the score's own event table, so what you see is what the music is doing. The narrator is Der Gouverneur, my Alpine philosopher voice. I host the open and the close.

License

The films are CC BY 4.0. Remix them, repost them, drop them into your own thing. Credit "Napkin Films / Organic Arts LLC" and link CC BY 4.0. Engine code (Napkin Films, ChipForge) is GPL-3.0-or-later. ElevenLabs voice audio is licensed content and is not redistributed.