Patent ID: 7769182

Claim:
A method for defining an index of a match between a content of two audio sources, comprising the steps of: a) defining a set of sampling parameters; b) sampling audio from a first source according to said sampling parameters, generating a first set of samples, and audio from a second source according to said sampling parameters, generating a second set of samples; c) selecting a sequential number of samples N which belong to said first set of samples and an identical number of samples N to be compared which belong to said second set of samples; d) transferring said first sequence of N samples to the frequency domain, generating a first sequence of N/2 frequency intervals, and transferring said second sequence of N samples to the frequency domain, generating a second sequence of N/2 frequency intervals; for said first sequence of N/2 frequency intervals, calculating the sign of the derivative; e) for said second sequence of N/2 frequency intervals, calculating the sign of the derivative and the absolute value of the derivative and calculating a total sum constituted by the sum of the absolute values of the derivative in each frequency interval comprised between a lower limit and an upper limit; f) for said second sequence of N/2 frequency intervals, calculating a partial sum constituted by the sum of the absolute values of the derivative in each frequency interval comprised between a lower limit and an upper limit, wherein the sign of the derivative in the frequency interval that belongs to said second sequence coincides with the sign of the derivative of the corresponding frequency interval in said first sequence; g) using the ratio between said partial sum and said total sum as an index of the match of said content of said audio sources.