To provide a method and an apparatus for enhancing the acoustic quality of a wideband-to-narrowband converted signal in which wideband speech signals must be converted to narrowband speech signals if the transmission medium or the destination terminal is constructed with narrowband constraints, and a typical wideband-to-narrowband conversion method is the elimination of frequencies of 3,400 Hz by using a low-pass filter and a down-sampler but this method produces muffled speech sound since the resulting narrowband signal has a flat frequency response.
In the apparatus, a bandwidth switching filter 68 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.
ANANTHAPADMANABHAN ARASANIPALAI K
DEJACO ANDREW P
| JPS62135022A | 1987-06-18 | |||
| JPS58198097A | 1983-11-17 |
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