Patent ID: 6725108
Filing Date: 2004-04-20
Classification: G10G,H04R

Abstract:
A system for analyzing an acoustic spectrum comprising:a computer with one or more memories and one or more central processing units; an audio input device that acquires an audio waveform in the time domain; means for conducting a spectral analysis process that evaluates the frequency content of the audio waveform at one or more discrete evaluation frequencies, the spectral-analysis process determining at each evaluation frequency a spectral amplitude representing the power spectral density of the waveform at the respective frequency, this set of spectral amplitudes versus frequency being called a power spectrum; a note analysis process that identifies a set of peaks in the power spectrum, finds low-integer relationships between the frequency of the peaks, and thereby determines which of the peaks belongs to a note contained in the audio waveform; wherein said note analysis process comprises the following steps: a. selecting the largest peak into a set of overtones comprising the note; b. sequentially comparing a candidate peak not yet in the set to those already in the set, said sequential comparisons being done in order of decreasing amplitude of the candidate peaks; c. for each of the comparisons, selecting the candidate peak into the set of overtones if and only if the candidate peak's frequency as well as the frequencies of all peaks already in the set are low-integer multiples of a common fundamental frequency, within a tolerance.