Method of evaluating speech

Claim 3

The method as recited in claim 1 wherein said standard of speech is selected by recording a human voice on a storage medium; and wherein said set of filters is selected to encompass the bandpass characteristics of the international telephone network (nominally 300 Hz to 3200 Hz).

Claim 4

The method as recited in claim 1 wherein said set of filters includes fifteen filters having center frequencies, cutoff frequencies, and bandwidths, respectively, as follows: ______________________________________ Number Center Freq. (Hz) Cutoff (Hz) Bandwidth (Hz) ______________________________________ 1 250 300 100 2 350 400 100 3 450 510 110 4 570 630 120 5 700 770 140 6 840 920 150 7 1000 1080 160 8 1170 1270 190 9 1370 1480 210 10 1600 1720 240 11 1850 2000 280 12 2150 2320 320 13 2500 2700 380 14 2900 3150 450 15 3400 3700 550 ______________________________________ wherein center frequency is defined as that frequency in which there is the least filter attenuation.

Claim 5

The method as recited in claim 3 wherein said set of filters includes sixteen filters, the sixteenth filter having a center frequency, a cutoff frequency, and a bandwidth as follows: ______________________________________ Center Cutoff Bandwidth No. Frequency (Hz) Frequency (Hz) (Hz) ______________________________________ 16 4000 4400 700 ______________________________________

Claim 6

The method as recited in claim 1 wherein said sample file of possibly distorted speech is recorded.

Claim 7

The method as recited in claim 5 wherein said possibly distorted speech is digitally recorded.

Claim 8

The method as recited in claim 1 wherein said spectra from said standard of speech file and said sample file of possibly distorted speech, and from said set of bandpass filters, is temporarily stored via parallel paths.

Claim 9

The method as recited in claim 1 wherein said spectra from said standard of speech file and said sample file of possibly distorted speech file, from said set of bandpass filters, is temporarily stored via a serial path.

Claim 10

An evaluative speech processor for evaluating the quality of speech carried by a voice communication system, comprising: means to select a digital file of undistorted speech representative of a speech standard satisfying specified criteria for said voice communication system; means to select a sample file of speech carried by said voice communication system for qualitative comparison with said file of standard speech, said sample file including at least one possibly distorted speech samples; means to input said standard speech file and said sample speech file into an evaluative speech processor; means to process said files through a plurality of critical bandpass filters having filter parameters representative of the bandpass characteristics of said voice communication system and of human auditory activity obtained from empirical observations; means to store temporarily the power spectra obtained from said standard speech file and said sample file, said power spectra providing a set of distorted-standard speech pairs; means to calculate a variance-convariance matrix from said set of distorted-standard speech pairs, wherein diagonal elements for each matrix are calculated according to ##EQU7## where MSW is the mean square within, N k is the number of observations in the kth vector, and S kp 2 is the pooled variance over the set of observations, and off-diagonal elements are calculated by ##EQU8## where r pp' is the pooled correlation coefficient, and S kp and S kp' are the pooled standard deviations for the k vectors; means to process Mahalanobis' D 2 Calculation data by the equation: D.sup.2 =(X.sub.1 -X.sub.2)Σ.sub.xx.sup.-1 (X.sub.1 -X.sub.2), where X 1 and X 2 are the sample mean vectors, and Σ xx -1 is the inverse of the variance-covariance matrix; and means to output said D 2 data, which represents the speech quality estimate of said sample speech file.

Claim 11

An evaluative speech processor for evaluating the quality of speech carried by a voice communication system, comprising: means to select a digital file of undistorted speech representative of a speech standard satisfying specified criteria for said voice communication system; means to select a sample file of speech carried by said voice communication system for qualitative comparison with said file of standard speech, said sample file including at least one possibly distorted speech samples; means to input said standard speech file and said sample speech file into an evaluative speech processor; means to process said files through a plurality of critical bandpass filters having filter parameters representative of the bandpass characteristics of said voice communication system and of human auditory activity obtained from empirical observations; means to store temporarily the power spectra obtained from said standard speech file and said sample file, said power spectra providing a set of distorted-standard speech pairs; means to calculate a variance-convariance matrix from said set of distorted-standard speech pairs, wherein diagonal elements for each matrix are calculated according to ##EQU7## where MSW is the mean square within, N k is the number of observations in the kth vector, and S kp 2 is the pooled variance over the set of observations, and off-diagonal elements are calculated by ##EQU8## where r pp' is the pooled correlation coefficient, and S kp and S kp' are the pooled standard deviations for the k vectors; means to process Mahalanobis' D 2 Calculation data by the equation: D.sup.2 =(X.sub.1 -X.sub.2)Σ.sub.xx.sup.-1 (X.sub.1 -X.sub.2), where X 1 and X 2 are the sample mean vectors, and Σ xx -1 is the inverse of the variance-covariance matrix; and means to output said D 2 data, which represents the speech quality estimate of said sample speech file.

Claim 12

The evaluative speech processor of claim 9 wherein said set of filters is selected to encompass the bandpass characteristics of the international telephone network (nominally 300 Hz to 3200 Hz).

Claim 13

The evaluative speech processor of claim 9 wherein said set of filters includes fifteen filters having center frequencies, cutoff frequencies, and bandwidths, respectively, as follows: ______________________________________ Number Center Freq. (Hz) Cutoff (Hz) Bandwidth (Hz) ______________________________________ 1 250 300 100 2 350 400 100 3 450 510 110 4 570 630 120 5 700 770 140 6 840 920 150 7 1000 1080 160 8 1170 1270 190 9 1370 1480 210 10 1600 1720 240 11 1850 2000 280 12 2150 2320 320 13 2500 2700 380 14 2900 3150 450 15 3400 3700 550 ______________________________________ wherein center frequency is defined as that frequency in which there is the least filter attenuation.

Claim 14

The evaluative speech processor of claim 11 wherein said set of filters includes sixteen filters, the sixteenth filter having a center frequency, a cutoff frequency, and a bandwidth as follows: ______________________________________ Center Cutoff Bandwidth No. Frequency (Hz) Frequency (Hz) (Hz) ______________________________________ 16 4000 4400 700 ______________________________________

Claim 15

The evaluative speech processor of claim 9 wherein said sample file of possibly distorted speech is recorded.

Claim 16

The evaluative speech processor as recited in claim 13 wherein said sample file of possibly distorted speech is digitally recorded.

Claim 17

The evaluative speech processor as recited in claim 9 wherein said spectra from said standard of speech file and said sample file of possibly distorted speech, and from said set of bandpass filters, is temporarily stored via parallel paths.

Claim 18

The evaluative speech processor as recited in claim 9 wherein said spectra from said standard of speech file and said sample file of possibly distorted speech file, from said set of bandpass filters, is temporarily stored via a serial path.