Tone Generator

The Tone Generator creates pure test tones and sweeps. Make a 1 kHz reference tone for checking levels, a 50 Hz tone to test a subwoofer, an A440 tuning note, or a 20 Hz–20 kHz sweep to find resonances and test speakers.

Square, sawtooth and triangle waves are built with band-limited (PolyBLEP) oscillators, so there is far less aliasing — the false, inharmonic tones naive generators produce at high frequencies.

Sine is computed directly from a phase accumulator. Square and sawtooth use PolyBLEP, which corrects the discontinuity at each wave edge with a small polynomial, greatly reducing aliasing. Triangle is computed directly from the phase; its harmonics fall off as 1/n², so aliasing is negligible. Sweeps use exact phase accumulation: logarithmic φ(t) = 2πf₀T/ln(f₁/f₀)·(e^{t ln(f₁/f₀)/T} − 1), linear φ(t) = 2π(f₀t + (f₁−f₀)t²/2T), so there are no zipper artefacts. A 4 ms fade in and out prevents clicks. The note readout converts the frequency to the nearest pitch and cents.