# US 2015/0032447 A1 · Determining a Harmonicity Measure for Voice Processing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0032447 A1 - Document ID: US20150032447A1 - Status: Published application - Kind: A1 - Application number: 14/384,842 - Filed: 2013-03-21 - Published: 2015-01-29 - Earliest claimed: 2012-03-23 - Assignees: Dolby Laboratories Licensing Corporation - Applicants: Dolby Laboratories Licensing Corporation - Inventors: David Gunawan; Glenn N. Dickins - Web page: https://patentgrep.com/patent/US20150032447A1 ## CPC - G10L 25/84: for discriminating voice from noise - G10L 2025/937: {Signal energy in various frequency bands} - G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING ## Abstract A method, an apparatus, and a computer-readable medium configured with instructions that when executed carry out the method for determining a measure of harmonicity. In one embodiment the method includes selecting candidate fundamental frequencies within a range, and for candidate determining a mask or retrieving a pre-calculated mask that has positive value for each frequency that contributed to harmonicity, and negative value for each frequency that contributes to inharmonicity. A candidate harmonicity measure is calculated for each candidate fundamental by summing the product of the mask and the magnitude measure spectrum. The harmonicity measure is selected as the maximum of the candidate harmonicity measures. ## Claims ### Claim at position 1 1-34. (canceled) ### Claim 35 A method of operating a processing apparatus to determine a measure of harmonicity of an audio signal, the method comprising: accepting the audio signal; determining a spectrum of an amplitude measure for a set of frequencies, including time-to-frequency transforming the signal to form a set of frequency components of the signal at the set of frequencies; and determining as a measure of harmonicity a quantity indicative of the normalized difference of spectral content in a first subset of frequencies corresponding to harmonic components of the audio signal and the sum of the spectral content in a second subset of frequencies corresponding to inharmonic components of the audio signal, the difference normalized by the sum of spectral content in the first and second subsets, all spectral contents being up to a maximum frequency and based on the amplitude measure. ### Claim 36 (depends on 35) A method as recited in claim 35, wherein the time-to-frequency transforming performs a discrete Fourier transform of a time frame of samples of the audio input signal, such that the set of frequencies are a set of frequency bins. ### Claim 37 (depends on 35) A method as recited in claim 35, wherein the amplitude measure is the square of the amplitude, the spectral content is a total energy determined as the sum of the squares of the amplitude up to the maximum frequency, and the measure of harmonicity is proportional or equal to the normalized difference between the total energy in the first subset and the total energy in the second subset normalized by the total energy in the first and second subsets, all total energies determined up to the maximum frequency. ### Claim 38 (depends on 35) A method as recited in claim 35, wherein the amplitude measure is the amplitude and the spectral content is determined as the sum of amplitudes. ### Claim 39 (depends on 35) A method as recited in claim 35, wherein whether or not a frequency is in the first or second subset is indicated by a mask defined over frequencies that include the first and second subsets, wherein the mask has a positive value for each frequency in the first subset and a negative value for each frequency in the second subset, and wherein the determining of the measure of harmonicity includes determining the sum over the frequencies of the product of the mask and an amplitude measure. ### Claim 40 (depends on 39) A method as recited in claim 39, wherein determining the difference comprises: determining one or more candidate fundamental frequencies in a range of frequencies, wherein each candidate fundamental frequency has an associated mask; obtaining the one or more associated masks for the one or more candidate fundamental frequencies by selecting the one or more associated masks from a set of pre-calculate masks or by determining the one or more associated masks for the one or more candidate fundamental frequencies; calculating a candidate measure of harmonicity for the one or more candidate fundamental frequencies; and selecting the maximum measure of harmonicity as the measure of harmonicity. ### Claim 41 (depends on 40) A method as recited in claim 40, wherein the determining the one or more candidate fundamental frequencies comprises detecting peaks in the amplitude measure spectrum of the signal. ### Claim 42 (depends on 41) A method as recited in claim 41, wherein the determining the one or more candidate fundamental frequencies further comprises determining the peaks in the amplitude measure spectrum at a finer frequency resolution than provided by the time-to-frequency transform. ### Claim 43 (depends on 39) A method as recited in claim 39, wherein a mask associated with a selected fundamental frequency includes a window of positive values of width a pre-defined fraction of the selected fundamental frequency for each of a subset of harmonics of the selected fundamental frequency. ### Claim 44 (depends on 39) A method as recited in claim 39, wherein the mask has a positive first value for all frequencies in the first subset and the negative of the first value for all frequencies in the second subset, such that summing the product of the mask and the amplitude measure spectrum can be carried out by add operations. ### Claim 45 An apparatus to determine a measure of harmonicity of an audio signal, the apparatus comprising: a spectrum calculator operative to accept the audio signal and calculate a spectrum of an amplitude measure for a set of frequencies, the spectrum calculator including a transformer to time-to-frequency transform the signal; a fundamental frequency selector operative to determine a candidate fundamental frequency in a range of frequencies; a mask determining element coupled to the fundamental frequency selector and operative to retrieve or calculate an associated mask for the candidate fundamental frequency; a harmonicity measure calculator operative to determine a measure of harmonicity for the candidate fundamental frequency by determining the sum over the set of frequencies up to a maximum frequency of the product of the associated mask and the amplitude measure, divided by the sum over the set of frequencies up to the maximum frequency of the amplitude measure; a maximum selector operative to select the maximum of candidate harmonicity measures determined by the harmonicity measure calculator for candidate fundamental frequencies in the range of frequencies. ### Claim 46 (depends on 45) An apparatus as recited in claim 45, wherein the time-to-frequency transforming performs a discrete Fourier transform of a time frame of samples of the audio input signal, such that the set of frequencies are a set of frequency bins. ### Claim 47 (depends on 45) An apparatus as recited in claim 45, wherein the amplitude measure is the square of the amplitude. ### Claim 48 (depends on 45) An apparatus as recited in claim 45, wherein the amplitude measure is the amplitude and the spectral content is determined as the sum of amplitudes. ### Claim 49 (depends on 45) An apparatus as recited in claim 45, wherein the fundamental frequency selector selects each frequency bin in the range of frequencies. ### Claim 50 (depends on 49) An apparatus as recited in claim 49, wherein the fundamental frequency selector is operative on an amplitude measure spectrum oversampled in frequency to obtain the candidate fundamental frequencies over a finer frequency resolution than provided by the time-to-frequency transform. ### Claim 51 (depends on 49) An apparatus as recited in claim 49, further comprising: a storage element storing a data structure of pre-calculate masks; a plurality of mask determining elements coupled to the storage element and operative to retrieve an associated mask for a different one of the frequency bins in the range of frequencies; and a plurality of harmonicity measure calculators, each harmonicity measure calculator couplet to a respective one of the mask determining elements to form, in combination, a harmonicity measure forming element operative to determine a measure of harmonicity using the associated mask retrieved by the mask determining element, wherein the harmonicity measure forming elements operate in parallel. ### Claim 52 (depends on 45) An apparatus as recited in claim 45, wherein the fundamental frequency selector comprises a peak detector to detect peaks in the amplitude measure spectrum of the signal. ### Claim 53 (depends on 45) An apparatus as recited in claim 45, wherein a mask associated with a selected fundamental frequency includes a window of positive values of width a pre-defined fraction of the selected fundamental frequency for each of a subset of harmonics of the selected fundamental frequency. ### Claim 54 (depends on 45) An apparatus as recited in claim 45, wherein the mask has a positive first value for all frequencies corresponding to harmonic content and the negative of the first value for all frequencies corresponding to inharmonic content, and wherein all frequencies correspond to either harmonic content or inharmonic content such that the harmonicity measure calculator determines the sum of the product of the mask and the amplitude measure spectrum by add operations.