Method and apparatus for objective speech quality measurements of telecommunication equipment
First Claim
1. Test apparatus comprising:
- a signal generator for supplying a test signal which has a spectral resemblance to human speech but which corresponds to more than one speaker, andanalysis means for receiving a distorted signal which corresponds to said test signal when distorted by equipment to be tested, and for analyzing said distorted signal to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener,said analysis means including means to split the signal into a plurality of spectral bands having bandwidths which vary with frequency.
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Accused Products
Abstract
A telecommunications testing apparatus comprising a signal generator which generates a speech-like synthetic signal, which is supplied to the input of a telecommunication apparatus to be tested. The distorted output of the telecommunications apparatus is supplied to an analyzer, which derives, for both the undistorted test signal and the distorted signal from the telecommunications apparatus, a measure of the excitation of the human auditory system generated by both signals, taking into account both spectral masking and temporal masking phenomena. The difference between the two excitations is then calculated, and a measure of the loudness of the difference is derived which is found to indicate to a high degree of accuracy the human subjective response to the distortion introduced by the telecommunications system.
45 Citations
65 Claims
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1. Test apparatus comprising:
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a signal generator for supplying a test signal which has a spectral resemblance to human speech but which corresponds to more than one speaker, and analysis means for receiving a distorted signal which corresponds to said test signal when distorted by equipment to be tested, and for analyzing said distorted signal to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener, said analysis means including means to split the signal into a plurality of spectral bands having bandwidths which vary with frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. Telecommunications testing apparatus comprising:
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a signal generator for supplying a test signal which has a spectral resemblance to human speech but corresponds to a more than one speaker, and analysis means for receiving a distorted signal which corresponds to said test signal when distorted by telecommunications apparatus to be tested, and for analyzing said distorted signal to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener; in which the analysis means is arranged to estimate the effect which would be produced on the human auditory system by said test signal, and to estimate therefrom the effect which would be produced on the human auditory system by said distortion. - View Dependent Claims (25)
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26. Telecommunications testing apparatus comprising:
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a signal generator for supplying a test signal which has a spectral resemblance to human speech but corresponds to a more than one speaker, and analysis means for receiving a distorted signal which corresponds to said test signal when distorted by telecommunications apparatus to be tested, and for analyzing said distorted signal to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener; in which the analysis means is arranged so as to generate said distortion perception to depend upon perceptual loudness of said distortion, and to depend nonlinearly upon the amplitude of said distortion.
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27. Telecommunications testing apparatus comprising:
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a signal generator for supplying a test signal which has a spectral resemblance to human speech but corresponds to a more than one speaker, and analysis means for receiving a distorted signal which corresponds to said test signal when distorted by telecommunications apparatus to be tested, and for analyzing said distorted signal to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener; in which the analysis means is arranged to generate a plurality of spectral component signals of said test signal and/or said distorted signal; in which the component signals have different bandwidths, and in which the component signal bandwidths are selected so they correspond to equal masking amplitudes for signals centred within each band.
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28. Telecommunications testing apparatus comprising:
- a signal generator for supplying a test signal, and analysis means arranged to;
(a) receive a distorted signal which corresponds to said test signal when distorted by telecommunications apparatus to be tested, (b) to decompose said distorted signal into a plurality of spectral component bands, the spectral component bands having bandwidths approximately evenly spaced in pitch, (c) to calculate the temporal masking of the distorted signal, (d) to form for each of the spectral component signals, the difference between the distorted signal and a correspondingly calculated test signal component for a plurality of successive temporal portions of the test signal; and (e) to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener by deriving a measure of the said spectral component differences over a plurality of said temporal portions and said spectral components, and a measure of the distribution of said differences over said temporal portions and spectral components.
- a signal generator for supplying a test signal, and analysis means arranged to;
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29. Telecommunications testing apparatus comprising:
- analysis means for receiving a distorted signal which corresponds to a test signal when distorted by telecommunications apparatus to be tested, and including means for generating a plurality of spectral component signals of said distorted signal, each said spectral component signal comprising a time sequence of successive spectral component values representative of component signal levels over a time interval, the time intervals being longer for lower frequency spectral component signals than for higher frequency spectral component signals,
in which the component signals have different bandwidths which vary with frequency. - View Dependent Claims (30)
- analysis means for receiving a distorted signal which corresponds to a test signal when distorted by telecommunications apparatus to be tested, and including means for generating a plurality of spectral component signals of said distorted signal, each said spectral component signal comprising a time sequence of successive spectral component values representative of component signal levels over a time interval, the time intervals being longer for lower frequency spectral component signals than for higher frequency spectral component signals,
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31. Apparatus for testing equipment for handling speech signals, said apparatus comprising:
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a signal generator for supplying a test signal, and analysis means arranged to receive a distorted signal which corresponds to said test signal when distorted by the apparatus to be tested, the analysis means including; means to decompose said distorted signal into a plurality of spectral component bands, the spectral component bands having different bandwidths which vary with frequency; means to calculate the temporal masking of the distorted signal by forming, for each of the spectral component signals, the difference between the distorted signal and a correspondingly calculated test signal component for a plurality of successive temporal portions of the test signal; and means to generate a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener by deriving measure of the said spectral component differences over a plurality of said temporal portions and said spectral components. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48)
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49. Apparatus for testing humanly perceptible distortion of speech signal processing said apparatus comprising:
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means for applying a test signal to speech signal processing circuits; means for measuring the distribution and interaction over time and frequency of the spectral component differences within a distorted test signal output from said speech signal processing circuits; and means for generating a distortion perception measure based on said distribution and interaction over time and frequency of the spectral component differences. - View Dependent Claims (50, 51, 52)
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53. A method of testing speech signal handling equipment to be tested, said method comprising:
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supplying a test signal to the speech handling equipment, said test signal having a spectral resemblance to human speech but which does not correspond to a single speaker conveying intelligent content, analyzing the test signal as distorted by said speech signal handling equipment; determining the extent to which the distortion of said signal will be perceptible to a human listener; and generating a distortion perception measure indicative of said determined extent; said step of analyzing including splitting the signal into a plurality of spectral bands having bandwidths which vary with frequency. - View Dependent Claims (54, 55, 56, 57, 58)
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59. A method of testing telecommunications apparatus comprising:
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analyzing a speech-like test signal which has a spectral resemblance to human speech but does not correspond to a single speaker conveying intelligent content, as distorted by said telecommunications apparatus; determining the extent to which the distortion of said signal will be perceptible to a human listener; and generating a distortion perception measure indicative of said determined extent; generating said test signal; passing said test signal through said telecommunications test apparatus; and
analyzing the distorted signal produced at the output of said telecommunications test apparatus;analyzing the extent to which said test signal would be perceptible to a human listener; deriving a measure of the difference between the perception of the test signal and of the distorted signal; and deriving said distortion perception measure in dependence upon said difference.
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60. A method of testing equipment for handling speech signals, said method comprising the steps of:
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supplying a test signal, receiving a distorted signal which corresponds to said test signal when distorted by the equipment under test, and decomposing said distorted signal into a plurality of spectral component bands, the spectral component bands having different bandwidths which vary with frequency; calculating the temporal masking of the distorted signal to form, for each of the spectral component signals, the difference between the distorted signal and a correspondingly calculated test signal component for a plurality of successive temporal portions of the test signal; and generating a distortion perception measure which indicates the extent to which the distortion of said signal will be perceptible to a human listener by deriving a measure of the said spectral component differences over a plurality of said temporal portions and said spectral components. - View Dependent Claims (61)
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62. Method for testing humanly perceptible distortion of speech signal processing circuits, said method comprising:
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applying a test signal to speech signal processing circuits; measuring the distribution and interaction over time and frequency of the spectral component differences within a distorted test signal output from said speech signal processing circuits; and generating a distortion perception measure based on said distribution and interaction over time and frequency of the spectral component differences. - View Dependent Claims (63, 64, 65)
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Specification