Time-Scale Modification of Complex Acoustic Signals in Noise
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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A new approach is introduced for time-scale modification of short- duration complex acoustic signals to improve their audibility. The method preserves an approximate time-scaled temporal envelope of a signal, thus capitalizing on the perceptual importance of the signals temporal structure, while also maintaining the character of a noise background. The basis for the approach is a subband signal representation, derived from a filter bank analysissynthesis, the channel phases of which are controlled to shape the temporal envelope of the time-scaled signal. Channel amplitudes and filter bank inputs are selected to shape the spectrum and correlation of the time-scaled background. The phase, amplitude, and input control are derived from locations of events that occur within filter bank outputs. A frame-based generalization of the method imposes phase consistency and background noise continuity across consecutive synthesis frames. The approach and its derivatives are applied to synthetic and actual complex acoustic signals consisting of closely spaced sequential time components. Time-Scale modification, Slow-motion audio replay, Complex acoustic signal, Signal enhancement, Noise background preservation, Improved audibility, Temporal envelope, Filter bank analysissynthesis, Sine-wave.