Some Systems for Speech‐Band Compression
作者:
Friederich Vilbig,
Kurt H. Haase,
期刊:
The Journal of the Acoustical Society of America
(AIP Available online 1956)
卷期:
Volume 28,
issue 4
页码: 573-577
ISSN:0001-4966
年代: 1956
DOI:10.1121/1.1908401
出版商: Acoustical Society of America
数据来源: AIP
摘要:
Speech‐band compression aims to reduce the frequency band width without impairing the desired informational content. Physical compression systems are of two types: spectrum‐alteration systems and vocoder (voice coding) systems. Spectrum alteration is not restricted to speech, is relatively simple to perform, but achieves only a compression factor of 3 to 5. Considerably higher ratios (10 to 20) are obtainable by vocoder‐type systems. Here, by a spectrum analysis on the transmitter side, a “pitch” frequency is extracted and a system function is derived. Both are then transmitted to a receiver where speech is synthesized. At the A. F. Cambridge Research Center, the following vocoder‐type systems are being developed and investigated: the scan vocoder with envelope scanning, the pulse vocoder in which the envelope is coded, and the formant vocoder in which the envelope is represented by three formant frequencies. By means of alterations and additions, the scan vocoder can be transformed into a pulse or a formant vocoder.
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