A 5-kHz-bandwidth low-bit-rate speech coder: Bandwidth, noisiness, and opinion scores

Noboru Harada, Hitoshi Ohmuro, Kazunori Mano

Research output: Contribution to journalArticlepeer-review


With the development of PCs, Internet technology, and mobile communications, the demand for low-bit-rate speech coding schemes as well as for high-information-level natural speech have increased in recent years. While naturalness increases with the use of speech signals of broad frequency bands, more information is needed for coding. In this paper, we propose a 5-kHz-band speech coding scheme that clarifies the relationships between the frequency band feeling, noisiness, and subjective opinions on quality by means of evaluation experiments using multiple frequency bands, while allowing selection between low bit rate and naturalness. The proposed scheme operates in three bit-rate modes, 7.8, 5.75, and 3.95 kbit/s. Subjective quality evaluation tests confirm that the coding scheme achieves quality almost equal to G.729 (3.4-kHz bandwidth, 8 kbit/s) and G.722 (7-kHz bandwidth, 48 kbit/s) at 5.75 kbit/s and quality higher than these at 7.8 kbit/s.

Original languageEnglish
Pages (from-to)110-119
Number of pages10
JournalSystems and Computers in Japan
Issue number14
Publication statusPublished - 2002 Dec 1
Externally publishedYes


  • 5-kHz bandwidth
  • CELP
  • Speech coding

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Information Systems
  • Hardware and Architecture
  • Computational Theory and Mathematics


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