RESPITE: The CASA Toolkit Page: Documentation: Block Library Index: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.
Harmonic Removal with FACTOR=3

Inputs Meaning Sample 1-D frame $\ge$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

Documentation for CTKv1.1.4 - Last modified: Thu Jun 28 12:34:11 BST 2001