Patent ID: 8340964

Claim:
A method of manipulating sound signal, the method comprising the steps of: a) obtaining a buffer of N samples of a sound signal; b) passing the buffer of N samples through a high pass filter (HPF), with the HPF having a predetermined cut-off frequency in the range of 20 Hz to 800 Hz; c) finding the power of the buffer of N samples using the equation: pwr = 1 N ⁢ ∑ k = 0 N ⁢ x ⁡ ( k ) * x ⁡ ( k ) where N is the number of samples in the buffer and k is the time index; d) averaging the power over a period of time where power is expressed as dB or as level and is calculated as level = 10 ⁢ ⁢ log 10 ⁢ ∑ i = 0 N_DEC ⁢ pwr ⁡ ( i ) where N_DEC is the number of buffers considered per decision; the signal passed through the HPF is processed by a voice activity detection device (VAD) to determine if the result from part d is speech or a pause, in the event the input is a pause, power calculated is expressed as pwr_sil, where the power is then averaged over a period of time, and expressed in dB as level_sil which is mathematically equal to is: level_sil=10 log 10 pwr_sil the power value (dB) is then exponentially averaged using the equation: level sil avg =α*level sil avg +(1−α)*level_sil, wherein α is a value between 0.01 and 0.99 e) the signal passed through the HPF is used as an input sequence x(n) in a Goertzel calculation s(n)=x(n)+2 cos(2πω)s(n−1)−s(n−2) to compute a sequence, s(n), the resulting sequence, s(n) is used to compute the DFTs at different frequencies (ω); f) the DFTs are altered to equal their absolute value and then stored in an array N_DEC×M wherein M equals the number of pre-selected frequencies of musical notes; g) histograms depicting energy distribution for each pre-selected frequency of musical notes are calculated and histograms bins with a higher value as compared to a pre-selected threshold are then summed and stored in a 1×M element array; h) a difference signal is calculated by taking the first difference between adjacent elements in the array depicted in step (g); i) calculating the standard deviation of the difference signal; j) selecting a bottom threshold for the power level; k) if the standard deviation of the difference signal is greater than the selected threshold (between 6 and 8), the signal is deemed to be a music signal, otherwise the signal is deemed to be speech or a pause, wherein fine tuning of the decision is based on average level of silence (level sil avg ) calculated in step (d) and if this level is below a preset threshold for a period representing 80% of the analysis frames a decision of silence is made.