A phaser is an audio signal processing technique used to filter a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low-frequency oscillator.

	Phaser audio effect A short, unprocessed string sample, followed by a few different phasing effects on the same sample
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Contents [hide] 1 Process 2 Structure 3 Usage 4 Similar effects 5 See also 6 References 7 External links

[edit]Process

Spectrogram of an 8-stage phaser modulated by a sine LFO applied to white noise.

The electronic phasing effect is created by splitting an audio signal into two paths. One path treats the signal with an all-pass filter, which preserves the amplitude of the original signal and alters the phase. The amount of change in phase depends on the frequency. When signals from the two paths are mixed, the frequencies that are out of phase will cancel each other out, creating the phaser's characteristic notches. Changing the mix ratio changes the depth of the notches; the deepest notches occur when the mix ratio is 50%.

The definition of phaser typically excludes such devices where the all-pass section is a delay line; such a device is called a flanger^[1]. Using a delay line creates an unlimited series of equally spaced notches and peaks. It is possible to cascade a delay line with another type of all-pass filter as in,^[2] this combines the unlimited number of notches from the flanger with the uneven spacing of the phaser.