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| Speaker system |
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| Speaker distortion compensator |
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| Resistively damped loudspeaker system |
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| Audio system with amplifier and signal device |
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| Loudspeaker system |
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| Hanging, positionable, speaker enclosure |
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| Digital duplex transmission system |
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Arrangement for the transmission of speech according to the channel vocoder principle
| Details |
Inventors: Reiss, Ruediger;
Assignee: Siemens Aktiengesellschaft (Berlin & Munich, DE)
Primary Examiner:
Assistant Examiner:
Attorney, Agent or Firm:
A synthesizer for a channel vocoder for the transmission of speech with considerable frequency band reduction in digital technology provides a reduction of circuit expense. This is accomplished, given non-recursive filters having finite impulse response, not with a weighting of the pulse-shaped excitation variable with the transmitted envelope values of the spectral channels, but with a time variance of the filters by weighting their filter coefficients with the transmitted envelope values. In addition, with proper dimensioning of the filter coefficients, an optimum speech quality of synthesized speech is obtained at the output of the synthesizer even given elimination of the transmission of a voiced/voiceless signal. |
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DETAILED DESCRIPTION The object of the invention is to provide a digital filter bank for a synthesizer of a channel vocoder constructed in digital technology which, given a relatively low technical expense, can guarantee an optimum speech quality of the generated synthetic speech.
According to the invention, and proceeding from an arrangement for transmission of speech according to a channel vocoder principle of the type initially mentioned, the above object is achieved in that the filter banks designed in digital technology comprise non-recursive, time-variant filters having finite impulse response (FIR filters).
Further, the excitation variable of the pulse generator is supplied at the input side to the filter bank with constant pulse amplitude.
The time-variance of the gain of the filter bank is produced in multipliers by multiplication of the filter bank coefficients by the envelope values transmitted in the rhythm of successive frames.
The present invention proceeds from the significant perception that it is of no significance for the impulse reply of a FIR filter whether the pulse sequence applied to its input is weighted with the transmitted envelope values or whether, on the other hand, the weighting occurs over a multiplication of the filter coefficients by the transmitted envelope values.
A filter bank, constructed in accordance with the present invention, as a time-variant filter bank to which the excitation variable of a pulse generator is supplied at its input side with constant amplitude reduces the multiplications to be carried out in the synthesizer and, therefore, the filter expense, in an extremely advantageous manner.
Given a first, preferred embodiment, the FIR filters to which the excitation variable is supplied at the input side respectively comprise an iterative network of N-1 identical time-delay stages with a maximum of N taps.
Each FIR filter has a plurality of switches corresponding to the taps, whose control inputs are connected to the taps.
Thereby, each switch connects the output of the multiplier to the filter output
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Audio Signal Processing 
