Python practice in Audio & DSP

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• Kill the DC

  A cheap mic added a DC offset that wastes headroom. Subtract the mean so the waveform swings symmetrically around zero.

  levels. Free room.

• Level It Out

  The take is too hot in places. Peak-normalize the signal so its loudest sample sits at full scale before it hits the converter.

  levels. Free room.

• Read the Meter

  The loudness meter needs a number. Compute the RMS level of the buffer, the effective loudness the ear responds to.

  levels. Free room.

• Tune the Oscillator

  First sound of the day: generate a clean sine at the requested frequency so the rest of the patch has something to work with.

  signals. Free room.

• Count the Crossings

  A rough pitch estimate counts how often the waveform crosses zero. Tally the sign changes, the cheapest frequency cue in the book.

  analysis. Account access required.

• Shape the Note

  A raw tone clicks on and off. Build an ADSR envelope so the note has a real attack, sustain, and release.

  envelopes. Account access required.

• Stack the Harmonics

  Build a richer tone additively: sum the harmonics with the given amplitudes over the fundamental.

  additive. Account access required.

• Window the Frame

  Before the analyzer FFTs each frame, taper it with a Hann window to tame spectral leakage.

  windows. Account access required.

• Measure the Energy

  Loudness scaling and Parseval's theorem both start here: the total energy of a signal is the sum of its squared samples. Compute it.

  spectral. Account access required.

• Slide the Kernel

  Apply a filter the honest way: convolve the signal with the kernel from scratch, two loops, no np.convolve.

  convolution. Account access required.

• Smooth the Signal

  Tame a noisy control signal with a one-pole low-pass: mix a little of the new input with a lot of the last output.

  iir. Account access required.

• Transform by Hand

  No library calls: compute the Discrete Fourier Transform straight from its definition so you know exactly what np.fft does.

  dft. Account access required.

• Carve with a Biquad

  Compute the RBJ cookbook coefficients for a resonant low-pass biquad, the second-order section behind every parametric EQ.

  iir. Account access required.

• Design the Filter

  Roll your own low-pass: a windowed-sinc FIR with unity DC gain, the workhorse of clean digital filtering.

  design. Account access required.

• Fast Transform

  The analyzer needs speed. Implement the radix-2 Cooley-Tukey FFT, splitting even and odd samples and recombining.

  fft. Account access required.

• Read the Decibels

  Faders and meters speak in decibels, not raw amplitude. Convert a linear amplitude to dBFS with the 20*log10 law, where unity gain reads zero.

  levels. Account access required.

• Build the Echo

  Add depth with a feedback echo: each repeat is a fraction of the last, fading into the distance.

  effects. Account access required.

• Compand the Signal

  Telephony squeezes dynamic range with mu-law companding before quantizing. Apply the mu-law encoder, the nonlinear curve that gives quiet sounds more bits.

  quantization. Account access required.

• Detect the Pitch

  Prove the tuner works: detect the fundamental of a tone with the YIN difference function and its cumulative-mean-normalized pick.

  pitch. Account access required.

• Play a Voice

  The whole instrument in one function: a sawtooth oscillator through a low-pass and an ADSR envelope. Synthesize the note.

  instrument. Account access required.