dsp

45 projects

105
The Jump-Up Bass
A Reese is two saws a few cents apart, so every harmonic is two lines with nothing at all between them: 84 dB of nothing at the sixth. Distortion doesn't add harmonics to it, the count is pinned at its ceiling before the first clipper even runs. What it does is put lines where there were none, and by the third nonlinearity the gap is within 17 dB of the lines either side of it. This one is also the first day where the sound isn't code: it's a patch, thirteen nodes of data, and the five steps you walk through are worked out from the signal path rather than written by hand.
sounddeepRecipes 2/12audio synthesis web-audio
103
The Moog Bass
The first of twelve basslines built a step at a time, and the step that matters turns out to be the filter you can't get from Web Audio. A Moog's ladder is four one pole stages with feedback around all four, and that feedback subtracts the input, which is what eats the bass: for an 8.5 dB resonant peak it pays 10.4 dB of fundamental while the peak itself rises 12.1 dB. Two cascaded BiquadFilterNodes put up the same peak within 0.1 dB and pay nothing at all, so at matched peaks the ladder sits 12.5 dB further down. First of twelve.
soundbuildRecipes 1/12audio synthesis web-audio
102
The Sidechain
The pump of house is a compressor on the pad keyed from the kick, and the release knob is the sound. Measured off the pad's own level: a kick every 469 ms pushes it down 16 dB, and with a 150 ms release it's more than 3 dB down for 82% of every beat, back in 378 ms. At 50 ms that's 51% and 220 ms, a dent. At 400 ms it never gets back, a quieter pad. The worklet compressor rendered offline agrees. Twelfth of twelve.
soundbuildPatches 12/12audio synthesis web-audio
101
The Organ Bass
The M1 organ bass under half of house is a Hammond in software: drawbars that hold, a percussion harmonic that comes in 17 dB above them and decays in 150 ms, and a click of 31 dB of high frequency in the first five milliseconds. All three read off the sound, the percussion to within 10 ms of its setting. It fires only on a note played alone, so a legato phrase gets it once, and that's the feel.
soundbuildPatches 11/12audio synthesis web-audio
100
The Snare
A 909 snare is two tones at 180 and 330 Hz and a burst of highpassed noise, and the tones decay faster than the noise, so every hit stops being a drum and becomes a hiss at some moment. Measured off the sound, that moment is 84 ms at half snappy, 203 at a quarter, and never arrives at full because the noise leads from the first millisecond. The two decays predict 91 and 202. Play it, or let it play the two and four.
soundbuildPatches 10/12audio synthesis web-audio
99
The Clap
A clap is four bursts of noise 10 ms apart and a tail. A drum machine gates one noise source, so every burst is fresh. A sampler layers one burst on itself, so every burst is the same noise, and a sound that repeats every 10 ms wears a comb of peaks every 100 Hz. Measured: the copied clap repeats exactly and its comb is 23 dB deep, the fresh one never comes closer than a third of the way and has no comb at all. Same envelope, same ear, different spectrum.
soundbuildPatches 9/12audio synthesis web-audio
98
The 909 Hat
A 909 hat is six square waves at 205, 254, 370, 304, 523 and 800 Hz, frequencies picked to share no period. Measured by sliding the sound against itself, the closest it ever comes to repeating is 49% different. Snap the same six onto a 50 Hz grid and it repeats exactly every 20 ms, and a tone appears where the metal was. Play it, tune it, or let it play house hats.
soundbuildPatches 8/12audio synthesis web-audio
97
The Acid Line
A 303 slide is a lag on the pitch in semitones, so it takes the same time whatever the interval. Measured off the sound, a semitone and an octave both get 63% of the way in 59.8 ms and 95% in 180 ms, and an octave covers twelve times the ground in that time rather than taking twelve times as long. The accent opens the filter 1.4 octaves and adds 3.5 dB, and leaving the level out makes an accented note measure quieter than a plain one.
soundbuildPatches 7/12audio synthesis web-audio
96
The Hoover
Pulse width does not filter, it deletes. A rectangle of width d has harmonic h at four over pi h times the sine of pi h d, so harmonic h is exactly silent whenever d is a multiple of one over h. Measured on a real rectangle against that formula, every harmonic lands within a thousandth of a dB, and sweeping the width takes each harmonic to silence exactly floor(h/2) times between nothing and a half. Play it, or let it play rave stabs.
soundbuildPatches 6/12audio synthesis web-audio
95
The Supersaw
Seven sawtooths spread across a detune, and the seven lines around every harmonic get h times further apart as you go up. Measured on A3 at 40 cents, the fundamental swells 53 dB and the beating dies at harmonic 36, where the voices are 183 Hz apart, against 43 predicted from where the clusters touch. At 80 cents it dies at 18 and at 10 cents it never does. That's why a supersaw beats at the bottom and hisses at the top.
soundbuildPatches 5/12audio synthesis web-audio
94
The FM Bass
Two sines, one modulating the other, and the spectrum is a Bessel function. Measured against the arithmetic at every ratio and index the page offers, the worst sideband is 0.18 dB out. At an index of 2.405 the first zero of J0 takes the note out of its own sound, 80 dB down while the sound stays loud, and a decaying index passes through that null 62 ms into every note, predicted at 61. At a ratio of 1 or 2 the folded sidebands land back on the note and the null only half happens.
soundbuildPatches 4/12audio synthesis web-audio
93
The Wobble
A wobble is a saw through a resonant lowpass swept by a tempo locked LFO, and it doesn't sweep, it steps. The filter peak can only land on a harmonic of the note, so on a 55 Hz saw it climbs a staircase of 32 harmonics from the third to the 45th, a fourth wide at the bottom and 0.39 of a semitone at the top, going round 4.6 times a second on an eighth note at 140. Sharp resonance lifts each step 18 dB, soft lifts it 6. Play it, or let it play a bassline.
soundbuildPatches 3/12audio synthesis web-audio
92
The Reese
The reese is two saws a few cents apart, and every harmonic beats at its own multiple of the detune. At 15 cents on A1 the fundamentals drift round each other every 2.09 s and the eighth harmonic beats 3.83 times a second, both read off the sound. The lowpass decides the fastest beat you hear: 5 Hz closed, 12 Hz open, and at 30 cents open it passes 15 Hz and the growl becomes grit. Play it, or let it play a bar of drum and bass.
soundbuildPatches 2/12audio synthesis web-audio
91
The 808
The 808 is one sine with a pitch envelope. It starts at 147 Hz and lands on 49 in 155 ms, and the tail takes 2.4 s to fall 60 dB. A phone speaker plays 1% of it, and 84% of that is the first 50 ms. Clipping it hard buys the phone under 3 dB. Playing it an octave up buys 10. Play it on the keys, or let it play itself.
soundbuildPatches 1/12audio synthesis web-audio
90
Bit Crush
The lo-fi knobs, measured. Eight bits puts the noise floor 48.9 dB down, a tenth off the textbook figure, and turns a note at -40 dB into 27% distortion. Four bits gives 25 dB and that quiet note comes out as nothing at all. Dither brings it back as a tone in hiss for 4.9 dB of noise, and holding samples at 6 kHz grows a 1 kHz tone two images at 5 and 7 kHz, -14 and -17 dB, where the sinc says they should be.
soundbuildSynthesis 15/15audio synthesis web-audio
89
The Mono Button
Most systems play the bass in mono, and a bass widened for headphones pays for it there. A 10 ms delay on one side reads as out of phase and takes 16 dB off a 55 Hz bass in the sum. A detuned pair pumps in mono every 1.6 s, 54 dB deep. Sum and difference combs are as wide as either and lose nothing at all, measured.
soundbuildSynthesis 14/15audio synthesis web-audio
88
The Chord Stab
A chord's shimmer is its tuning. In equal temperament the third of a C major is 13.7 cents sharp of 5:4, so the root's fifth harmonic and the third's fourth miss by 10.4 Hz and beat that fast, measured off the sound, swelling 15 dB. In just tuning the same pair sits dead still. A minor third beats faster, and a 250 ms stab still holds two and a half swells of it.
soundbuildSynthesis 13/15audio synthesis web-audio
87
Warm and Harsh
Distortion is a curve, and everything people say about warm and harsh is a claim about its shape. Measured at the same distortion, a soft clip's harmonics fall 39 dB an octave and a hard clip's fall 12. Even harmonics need an asymmetric curve, and on two tones they cost a note two octaves down that nobody played, at -29 dB.
soundbuildSynthesis 12/15audio synthesis web-audio
86
Noise and the Hat
Noise has a colour, and the colour is a number: white is flat, pink falls 3 dB an octave, brown falls 6, measured. A hi-hat is what noise is for, and the 808's is six square waves chosen to share no harmonic. How little pitch that leaves is a number too, 45% for the six and 16% for the finished hat.
soundbuildSynthesis 11/15audio synthesis web-audio
85
The Pump
Sidechain pumping, the bass ducking under every kick, is done for loudness. Measured at the same peak, it buys about half a loudness unit at best, costs 1.5 without lookahead, and a loudness meter shows 2.4 LU of a 15 dB duck. The last part of the series, and the one where the reason turns out to be the groove.
soundbuildSynthesis 10/15audio synthesis web-audio
84
The Grime Square
A pulse wave has one knob, its width, and the width decides which harmonics do not exist. At half it is a square and every even harmonic is gone. At a third, every third. At a quarter, every fourth. Measured, exactly, and then the naive digital square measured against the exact one.
soundbuildSynthesis 9/15audio synthesis web-audio
83
The Wobble
A saw through a resonant lowpass with the cutoff swept by an LFO at the tempo. Sweep it in hertz and the wobble sounds open 80% of the time, because the ear hears octaves. And however you sweep it, the resonance cannot keep up, 3 dB short at half notes and 6 dB short at sixteenths.
soundbuildSynthesis 8/15audio synthesis web-audio
82
The Supersaw
Seven saws spread across thirty cents is the sound of every trance lead. Everyone argues about how many voices. Measured, the movement is about 2 dB whether you stack two or sixteen, and what more voices buy is that the shimmer never repeats, but only if the spacing is uneven. Evenly spaced, seven voices loop every 3.1 seconds.
soundbuildSynthesis 7/15audio synthesis web-audio
81
The 808 on a Phone
A phone speaker hears one per cent of a clean 808, and 93% of that is the first 60 milliseconds. Saturation does not bring the energy back, it moves it later into the body of the note. Drive makes a sub last on a phone. It does not make it louder.
soundbuildSynthesis 6/15audio synthesis web-audio
80
The Reese
Two saws seven cents apart, into a lowpass, into saturation. The bass under most of jungle, built from the last four parts. Saturation flattens its swell from 6.4 dB to under 1, and cannot stop the sub vanishing 60 dB down every four and a half seconds. That is why there is a sine under every Reese.
soundbuildSynthesis 5/15audio synthesis web-audio
79
One Detune, Ten Speeds
Two saws seven cents apart is the Reese, the bass under most of jungle. Detune them and they beat, but a saw is a stack of harmonics and the tenth one beats ten times faster than the first. One knob, and every harmonic moves at its own speed.
soundbuildSynthesis 4/15audio synthesis web-audio
78
The Click Is Not the Note
A pure 55 Hz sine has one frequency in it, and it still clicks when the note starts. How much depends on where the wave was at that instant, by 19 dB. The click is the envelope, and the attack is a filter on it.
soundbuildSynthesis 3/15audio synthesis web-audio
77
Where the Filter Really Cuts
The cutoff dial on a synth is only telling the truth at one setting of the resonance dial. Turn the resonance to 2 and a cutoff reading 1,000 Hz cuts at 1,485. Measured off the filter, not the diagram.
soundbuildSynthesis 2/15audio synthesis web-audio
76
Stack Sines, Get a Saw
A sawtooth is not a thing a synth has, it is a stack of sine waves each 1/n as loud as the first. Build it one sine at a time and listen to it turn into the sound every bass patch starts from.
soundbuildSynthesis 1/15audio synthesis web-audio
74
The Glass That Keeps Ringing
How long a glass rings and how narrowly it listens are the same number. Measure it both ways and they agree, unless you sweep past it too fast, and then one of them is 64% wrong.
soundbuildaudio physics dsp
73
The Note That Disappears
Wobble a note's pitch fast enough and it stops being a wobble and becomes a chord. Turn the depth to 2.405 and the note you started with is 132 dB down, while everything around it carries on.
soundbuildaudio web-audio maths
63
Which Is Louder
Two clips with identical peak levels, and one is obviously louder. Your answers reveal which of three measures you are actually following, and it is not the one on the meter.
sounddeepaudio dsp psychoacoustics
57
The Wedge You Can Bow In
A bowed string will only speak inside a wedge of bow force and bow position. Two boundaries, two different power laws, and the gap between them closes near the bridge.
sounddeepaudio physics web-audio
56
Blow Into a Tube
A clarinet with no oscillator in it. A tube and a flap of cane, and the note is what the loop between them settles on.
sounddeepaudio physics web-audio
55
One Knob, Three Sounds
A tone whose loudness wobbles. Speed the wobble up and it becomes three separate notes, without the signal changing in any way at all.
soundpsychoacoustics audio dsp
54
The Shape You Cannot Hear
Draw a spectrum, then rearrange its phases. The waveform becomes unrecognisable, the sound does not change, and the peak moves by six decibels.
soundaudio dsp psychoacoustics
51
Where the Fundamental Goes
Drag one number and the note you are listening to disappears while the sound gets louder. Bessel functions say exactly where.
soundaudio dsp maths
46
Two Numbers Make a Vowel
A vowel is two bumps in a spectrum. A voice can only send them at multiples of its own pitch, and a high voice cannot send enough.
soundpsychoacoustics audio dsp
39
A Tone in Neither Ear
The same noise in both ears, with one narrow band phase-inverted on the right. Each ear alone is featureless. Together they produce a pitch.
soundpsychoacoustics audio dsp
37
The Wheel Goes Backwards
Two wheels on one shaft, one seen continuously and one at 24 frames a second. Half of all speeds make the second wheel spin the wrong way.
perception dsp animation
35
Which Half Matters
A Fourier transform splits an image into sizes and offsets. Throw away the sizes and you can still read it. Throw away the offsets and you cannot.
dsp vision algorithms
28
One String
A buffer of noise and a two-sample average. That is a plucked string, and it cannot be tuned properly, for a reason you cannot fix.
soundweb-audio dsp synthesis
26
The Sound Of Sorting
Four algorithms doing the same job, with their comparison counts checked against the theory that predicts them.
soundalgorithms web-audio dsp
24
Circles All The Way Down
Draw any closed shape and it turns out to be a stack of rotating circles. Provably, and with a receipt.
dsp geometry generative
19
Hollow
Add a sound to a copy of itself a millisecond late and specific frequencies vanish, at places you can calculate exactly.
soundweb-audio psychoacoustics dsp