Method for the location of a speaker and the acquisition of a voice message, and related system

Claim 3

A method according to claim 1, including the operation of reconstructing the said acoustic event using the said acoustic signals in conjunction with delays calculated on the basis of the estimation of the said first signals.

Claim 4

A method according to claim 2, including basing the said reconstruction of the acoustic event on a modeling of the acoustic signal to be reconstructed substantially according to the formula: s(t)=a.sub.0 s.sub.0 (t)+a.sub.1 s.sub.1 (t+δ.sub.1 (t))+a.sub.2 s.sub.2 (t+δ.sub.2 (t))+a.sub.3 s.sub.3 (t+δ.sub.3 (t)) in which s(t) is the said acoustic signal to be reconstructed, so(t), s 0 (t), s 1 (t), s 2 (t), s 3 (t) are the said acoustic signals δ 1 (t), δ 2 (t), δ 3 (t) are the said delays, and a 0 , a 1 , a 2 , a 3 are numerical coefficients.

Claim 5

A method according to claim 1, wherein the said acoustic signals are converted into digital format after measurement.

Claim 6

A method according to claim 4, wherein the said conversion into digital format occurs at a given sampling frequency which is higher than a frequency band of the said acoustic event.

Claim 7

A method according to claim 1, wherein the operation for generating the said first signals on the basis of the said acoustic signals comprises the phases of: extracting sampling frames from the said acoustic signals, calculating an integral transform from the said frames, calculating cross power spectra for a plurality of pairs of the integral transform of the said frames, calculating an antitransform of the said cross power spectra.

Claim 8

A method according to claim 6, wherein the phase for extracting the frames comprises the phases of: extracting frames having predetermined lengths t f , corresponding to a predetermined number N of samples, with a pitch t a , weighting the said frames by means of a window.

Claim 9

A method according to claim 7, wherein the said window is a Blackman window.

Claim 10

A method according to claim 6, wherein when a sampling frequency F c =48 kHz, N is selected such that it is of the order of 1024 and t f is of the order of 21.33 ms and t a is of the order of t f /2=10.66 ms.

Claim 11

A method according to claim 6, wherein the integral transform of the frames is a Fourier transform.

Claim 12

A method according to claim 10, characterized in that the Fourier transform is a fast Fourier transform or FFT.

Claim 13

A method according to claim 6, wherein the said cross power spectra are normalised cross power spectra.

Claim 14

A method according to claim 5, wherein the phase of calculating the cross power spectra comprises: the phase of calculating for each of said pairs of the transform a vector ρ i having n components substantially in accordance with the formula ρ.sub.i =FFT.sup.-1 [Y.sub.j ] when j=1, 2, 3, the pairs being X 0 , X 1 ; X 0 , X 2 ; X 0 , X 3 ; and the l-th complex generic component of the vector Y j being defined as: ##EQU4## in which X j * is the conjugate complex vector of the vector X j .

Claim 15

A method according to claim 13, characterized in that the components of the vector ρ j are normalised.

Claim 16

A method according to claim 1, wherein the operation for generating the said first signals on the basis of the said acoustic signals comprises the phases of: extracting sampling frames from the said acoustic signals, calculating an integral transform from the said frames, calculating cross power spectra for a plurality of pairs of the integral transform of the said frames, calculating an antitransform of the said cross power spectra, wherein the phase of calculating the cross power spectra comprises: the phase of calculating for each of the pairs a vector ρ i having n components substantially in accordance with the formula ρ.sub.i =FFT.sup.-1 [Y.sub.j ] when j=1, 2, 3, the pairs being X 0 , X 1 ; X 0 , X 2 ; X 0 , X 3 ; and the l-th complex generic component of the vector Y j being defined as: ##EQU5## in which X j * is the conjugate complex vector of the vector X j , and wherein the method includes the phase of estimating the relative delay between pairs of frames of signals which comprises the phase of using the vector ρ j to calculate an index of coherence between the frame x 0 and a frame obtained by disphasing the frame x j by a number of samples i corresponding to a delay τ i =i/F c , equivalent to an index of coherence between the acoustic signal S 0 and the acoustic signal S j disphased by a delay τ i .

Claim 17

A method according to claim 12, wherein the first signals comprise coherence functions C j (t, τ) consisting of the vectors ρ j respectively.

Claim 18

A method according to claim 6, wherein the sample frames are extracted in pairs each comprising a first frame present in each pair, and a second frame selected from the frames which are different from the first frame common to all the pairs such that there is one pair for each of the frames different from the said first frame.

Claim 19

A method according to claim 6, wherein the said antitransform is an inverse Fourier transform.

Claim 20

A method according to claim 18, wherein the said inverse Fourier transform is an inverse fast Fourier transform or FFT.

Claim 21

A method according to claim 1, wherein the said first signals are estimated by means of filtering and interpolation.

Claim 22

A method according to claim 20, wherein the filtering of said first signals is activated by the use of at least one finite impulse response filter or FIR.

Claim 23

A method according to claim 1, wherein the said first signals are submitted to an operation for the search of the maximum of the first signals to generate second signals.

Claim 24

A method according to claim 12, wherein the first signals comprise coherence functions C j (t, τ) consisting of the vectors ρ j respectively, wherein the said first signals are submitted to an operation for the search of the maximum of the first signals to generate second signals, and wherein the phase of searching for the maximum comprises the phases of: searching for the maximum of the said coherence functions, filtrated and interpolated, C j ' (t, τ) when a delay τ' is varied, generating functions M j (t) defined substantially according to the formula M.sub.j (t)=maxC.sub.j '(t,τ') τ' when t is varied, and calculating the delays (δ 1 , δ 2 , δ 3 ) as delays δ j (t)=τ' max corresponding to the functions M j (t).

Claim 25

A method according to claim 1, wherein the phase of detecting the said acoustic event comprises the phases of: generating a detection signal on the basis of the said second signals, detecting that the detection signal has passed a predetermined threshold.

Claim 26

A method according to claim 12, wherein the first signals comprise coherence functions C j (t, τ) consisting of the vectors ρ j respectively, the said first signals are submitted to an operation for the search of the maximum of the first signals to generate second signals, wherein the phase of searching for the maximum comprises the phases of: searching for the maximum of the coherence functions, filtrated and interpolated, C j '(t, τ') when a delay τ' is varied, generating functions M j (t) defined substantially according to the formula ##EQU6## when t is varied, and calculating the delays (δ 1 , δ 2 , δ 3 ) as delays δ j (t)=τ' max corresponding to the functions M j (t), wherein the phase of detecting the said acoustic event comprises the phases of: generating a detection signal on the basis of the said second signals, detecting that the detection signal has passed a predetermined threshold, and wherein the said detection signal is substantially generated according to the formula d(t)=max[M.sub.1 (t),M.sub.2 (t),M.sub.3 (t)] in which d(t) is the said detection signal.

Claim 27

A method according to claim 1, wherein the method comprises the operation of locating at any moment the said acoustic event on the basis of delays calculated on the basis of the estimation of signals obtained by antitransformation of the said first signals, wherein the operation for generating the said first signals on the basis of the said acoustic signals comprises the phases of: extracting sampling frames from the said acoustic signals, calculating an integral transform from the said frames, calculating an antitransform of the said cross power spectra, and wherein the operation for locating the said acoustic event comprises the phases of: calculating a branch of a hyperbola having its focus at one of the two detection points, for any pair of detection points corresponding to the pairs of frames, calculating an area, defined by the said branches of a hyperbola, inside which the acoustic event is located.

Claim 28

A method according to claim 1, wherein the operation of generating said first signals on the basis of said acoustic signals comprises the phases of: calculating an integral transform from the said acoustic signals, and calculating cross power spectra for a plurality of pairs of the integral transform, wherein the said cross power spectra are normalized cross power spectra.