Enhanced conversion of wideband signals to narrowband signals

Details Enhanced conversion of wideband signals to narrowband signals Enhanced conversion of wideband signals to narrowband signals

2006-09-22

2009-08-18

Nguyen, Hanh (Department: 2416)

Data processing: speech signal processing, linguistics, language

Speech signal processing

For storage or transmission

C704S205000, C370S328000

Reexamination Certificate

active

07577563

ABSTRACT:
Wideband speech signals must be converted to narrowband speech signals if the transmission medium or the destination terminal is constructed with narrowband constraints. A typical wideband-to-narrowband conversion method is the elimination of frequencies above 3400 Hz using a low pass filter and a down sampler. However, this method produces a muffled speech sound since the resulting narrowband signal has a flat frequency response. Methods and apparatus are presented herein to enhance the acoustic quality of a wideband-to-narrowband converted signal. A bandwidth switching filter is used to emphasize a mid-range frequency portion of the wideband signal so that the resulting narrowband signal has a non-flat frequency spectrum.

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