What is "flanging"

Flange \Flange\, v. t. [imp. & p. p. Flanged (fl[a^]njd); p. pr. & vb. n. Flanging (fl[a^]n"j[i^]ng).] (Mach.) To make a flange on; to furnish with a flange.

n. (context music English) a time-based audio effect produced when two identical signals are mixed together, but with one signal time-delayed by a small and gradually changing amount, usually smaller than 20 milliseconds.

Flanging is an audio effect produced by mixing two identical signals together, one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resulting frequency spectrum, related to each other in a linear harmonic series. Varying the time delay causes these to sweep up and down the frequency spectrum. A flanger is an effects unit that creates this effect. In some cases the two signals will become so close that it almost fades away to oblivion called "sucking air." It has also been called the "Darth Vader effect."

Part of the output signal is usually fed back to the input (a "re-circulating delay line"), producing a resonance effect which further enhances the intensity of the peaks and troughs. The phase of the fed-back signal is sometimes inverted, producing another variation on the flanging sound.