definition v1 of flanger

A flanger is a human-made audio effect technique that produces a sweeping comb-filter 'jet' sound by summing a signal with a short delayed copy of itself whose delay length is slowly modulated by a low-frequency oscillator. Mechanism: the dry signal is mixed with a delayed copy at delay time tau(t); tau(t) is modulated by an LFO within a narrow band (roughly 0-20 ms, where the delayed copy stays correlated with the dry); the sum exhibits comb filtering — regularly spaced notches where the delayed wave cancels the dry — and as tau(t) sweeps, the notches sweep the spectrum, producing the characteristic whooshing jet sound. Parameters: (1) delay range / modulation depth (typically 0-15 ms; beyond ~20 ms the effect becomes chorus or echo and loses its jet character); (2) LFO rate (typically 0.01-10 Hz, commonly 0.1-0.5 Hz); (3) LFO waveform (sine, triangle, random); (4) wet/dry mix ratio; (5) optional feedback of the wet signal back into the delay line (regeneration), which deepens the comb notches. It is distinct from chorus (delay times of tens to hundreds of ms with per-channel detuning, thickening rather than jetting), from echo (delays of ~100 ms or more with audible repeats), and from time-stretching (which rescales the whole spectrum). Persistence mechanism: the technique is fixed by its algorithmic recipe (short delay line, LFO-modulated delay, wet/dry summation, optional feedback) and persists as reusable DSP code, effect plugins, and hardware units in audio toolkits and studio practice. [formal: flanger | substrate: behavior | horizon: hours | explicit: yes | epoch: 0.01]