TASI Quality - Effect of Speech Detectors and Interpolation

Abstract

This article describes tests made to select design parameters for the speech detectors in the TASI system. Results of subjective tests carried out to determine maximum permissible loading of TASI circuits during busy hours are also described. Finally, conclusions drawn from observations on a working TASI system are given. These observations indicate that TASI is a more satisfactory method of increasing transatlantic cable capacity than alternate methods, such as the use of 2‐kc channel banks.

Adapted packet speech interpolation

“…The APSI input buffer technique is a novel approach to the buffering and variable rate encoding required by the APSI system. From equations (3) and (4) we note that it is not possible to determine the analogue to digital encoding rate before the number of active sources a, is determined. The value a, is determined by examining the output of S silence detectors at the end of the ith frame.…”

Real-time implementation and evaluation of an adaptive silence deletion algorithm for speech compression

“…The first speech detectors for TASI were based on an analog averaging detector operating on a 500 to 3000 Hz bandwidth, with a fixed threshold to differentiate speech and silence intervals [19]. To prevent the loss of weak syllables, a hangover was incorporated to prevent the release of the speech detector until the speech power remained below the threshold for 240 ms.…”