HarmonicRemoval

The HarmonicRemoval block implements an algorithm for removing higher harmonics from spectral slices. This is a useful form of post-processing to apply to summary autocorrelations as it removes potentially distracting peaks that are not due to an F0 of one of the sources present.

The algorithm works by repeatedly subtracting a frequency stretched copy of the spectral slice from itself. The slice is first stretched by a factor of 2 and subtracted, then by a factor of 3 and so on up to a factor of FACTOR (see figure below). A suitable value of FACTOR is usually about 2, 3 or 4. After the multiple subtractions the spectral slice is half-wave rectified to remove any negative components.

Harmonic removal with a FACTOR of 3.

Inputs	Meaning	Sample	1-D frame	2-D frame
in1	frames of spectral data	No	Yes	No

Outputs	Meaning
out1	spectral data after harmonic removal

Parameters	Type	Default	Meaning
FACTOR	Integer	-	Number of frequency multiples to subtract