広帯域信号の狭帯域信号への強化された変換

Japanese Patent JP5199147

B2

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.

Caled H. L-Murray
Alasani Parai K. Anansa Pad Manaburn
Andrew P. Dejaco

JP2009033854A

May 15, 2013

February 17, 2009

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JP5076062A
JP7058709A
JP4263528A
JP11032014A
JP11331957A
JP10078796A
JP4213262A
JP10093689A
JP2000101572A

US6349197

Kurata Masatoshi
Satoshi Kono
Makoto Nakamura
Yoshihiro Fukuhara
Takashi Mine
Toshio Shirane
Sadao Muramatsu
Nobuhisa Nogawa
Kocho Chojiro
Naoki Kono
Katsu Sunagawa
Tetsuya Kazama
Katsumura Hiro
Shoji Kawai
Tatsushi Sato
Takashi Okada
Mihoko Horiuchi
Takenori Masanori
Takuzo Ichihara
Yamashita Gen

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