Fundamental frequency extracting system
OwnerHarald E. W. Bodeinventor
Life of this patent
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Abstract
A system for extracting the fundamental frequency or pitch of complex waves such as voice, musical instruments or other audio signals. Separate channels extract the fundamental frequency component when it is present in successively wider frequency bands, the frequency intervals between which are equal or less than an octave. Control signals generated in response to the presence of the fundamental components in any lower frequency channel inhibit each of the higher frequency channels thereby reducing the possibility of an overtone being detected as a fundamental frequency component of the complex wave.
Claims13
A system for extracting the fundamental frequency component of a complex wave such as the pitch of a voice or of an instrument, which system comprises a plurality of channels each having a single means for detecting the fundamental component of said wave when it is present in any of a plurality of successively wider bands of frequency, each being wider than its preceding band by a frequency increment not exceeding an octave of the highest frequency of the preceding band, and means responsive to the detection of said fundamental component in each of said bands for generating a control signal, a plurality of gating means for applying said control signal through separate ones of said gating means, to each of said channels for said bands of frequency higher than the channel generating said control signal for inhibiting the detection of said fundamental component in each and all of said higher frequency bands.
A system for extracting the fundamental frequency component of a complex wave such as the pitch of a voice or of an instrument, which system comprises a plurality of channels each having means for detecting the fundamental component of said wave when it is present in any of a plurality of successively wider bands of frequency, each being wider than its preceding band by a frequency increment not exceeding an octave of the highest frequency of the preceding band, means responsive to the detection of said fundamental component in each of said bands of frequency lower than any other of said bands for generating a control signal and applying said control signal to each of said channels for said other bands inhibiting the detection of said fundamental component in each of said other bands, said detecting means comprising a plurality of fundamental frequency extractor means which are responsive to said fundamental component in said successively wider bands having highest frequencies of f.sub.1, f.sub.2, f.sub.3 . . . f.sub.N-1, f.sub.N where said increment, (f.sub.2 -f.sub.1), (f.sub.3 -f.sub.2), . . . (f.sub.N -f.sub.N-1) does not exceed said octave such that (f.sub.2 -f.sub.1).ltoreq.f.sub.1, (f.sub.3 -f.sub.2).ltoreq.f.sub.2 . . . (f.sub.N -f.sub.N-1).ltoreq.f.sub.N-1), a plurality of said channels each having a separate one of said extractor means therein, and said extractor means having low pass filter means having cutoff frequencies of said frequencies f.sub.1, f.sub.2, f.sub.3, . . . f.sub.N-1, f.sub.N respectively in different ones of said channels, said inhibiting means comprising means operatively connected in each of said channels at the output of the extractor means thereof, except for said channel having said low pass filter means of cutoff frequency f.sub.N therein, for generating control voltages upon detection of the fundamental frequency component within the band passed by the low pass filter means therein, and means for applying said control voltages from each of said channels having low pass filter means of cutoff frequency lower than any other of said channels to each of said other channels for inhibiting said other channels.
Dependencies are inferred from the claim text.