| 摘要 |
A measurement method for evaluating the disturbances in an audio signal or test signal ( 1 a, b) by comparing it to an undisturbed reference signal ( 1 c, d). After being prefiltered ( 2 ) using the transfer functions of the outer and middle ear, the input signals are converted to a time-pitch representation by an perceptually adapted filter bank ( 3 ). Squares of absolute values ( 5 ) of the filter output signals are calculated (rectified), and the filter outputs are convoluted with a spreading function ( 4 ). Convolution can take place either before or after rectification. Level differences between the test and reference signals as well as linear distortions of the reference signals are compensated for in step ( 7 ) and evaluated separately. In step ( 8 ), a frequency-dependent offset is then added in order to model the residual noise of the ear, and the output signals are spread over time ( 9 ). Part of this time spreading operation can take place directly after rectification in step ( 4 ) in order to reduce computing time. After the time spreading step ( 8 ) (low-pass filtration), subsampling of the signals may then be performed. By comparing the resulting aurally compensated time-frequency patterns of the test and reference signals ( 1 a, b and 1 c, d), it is possible to calculate a series of output quantities in step ( 10 ), which provide an estimate of the discernible disturbances.
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