Extracts the time-varying spectral envelope (.for file) from a spectral analysis file (.ana). The spectral envelope can be extracted either by equal frequency bands (Mode 1) or equal pitch intervals (Mode 2). You can also choose the resolution of the analysis: a larger number of bands or larger pitch interval is more general, less accurate. An identical extraction process is built into several processes in the spectral suite. MODES 1. Formants by frequency: frequency-based extraction of spectral envelope 2. Formants by pitch: pitch-based extraction of spectral envelope PARAMETERS channels - Mode 1: No. of frequency channels per point used to extract spectral contour (fewer more accurate) Range: 1-100
bands - Mode 2: No. of pitch
bands per
octave used to extract spectral contour (greater more
accurate)Range:
1-12
NOTES In frequency mode (1), the pitch interval of the band gets progressively smaller with higher frequency. Similarly, a pitched sound's higher harmonics have progressively smaller intervals. So sound with a lot of high-frequency detail may be more suited to a frequency-based extraction. In pitch mode (2), the pitch interval (in semitones) stays the same*. The frequency range covered by this interval will therefore be progressively wider with higher frequency. (In music, an interval is a frequency ratio — an octave is 2/1 — so although it appears to us to have the same gap, in fact it covers a progressively wider range of frequencies as we go higher in pitch.) (*Presumably a semitone resolution is not possible in the extreme bass: the second-lowest analysis frequency band from c. 43 - 86Hz, covers an interval of about 11 semitones.)
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