Enhanced conversion of wideband signals to narrowband signals
First Claim
1. A device, comprising:
- a first element for creating a synthesized wideband speech signal; and
a second element for enhancing the synthesized wideband speech signal, wherein the second element further comprises;
a post-filter element that outputs a post-filtered signal; and
a bandwidth switching filter for emphasizing a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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Accused Products
Abstract
Wideband speech signals must be converted to narrowband speech signals if the transmission medium or the destination terminal is constructed with narrowband constraints. A typical wideband-to-narrowband conversion method is the elimination of frequencies above 3400 Hz using a low pass filter and a down sampler. However, this method produces a muffled speech sound since the resulting narrowband signal has a flat frequency response. Methods and apparatus are presented herein to enhance the acoustic quality of a wideband-to-narrowband converted signal. A bandwidth switching filter 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.
30 Citations
5 Claims
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1. A device, comprising:
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a first element for creating a synthesized wideband speech signal; and a second element for enhancing the synthesized wideband speech signal, wherein the second element further comprises; a post-filter element that outputs a post-filtered signal; and a bandwidth switching filter for emphasizing a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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2. A method for transmitting wideband waveforms originating in a wireless communication system, comprising:
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creating, by a wireless communication device, a synthesized wideband speech signal; and enhancing, by the wireless communication device, the synthesized wideband speech signal, wherein the enhancing further comprises; post-filtering the synthesized wideband speech signal and outputting a post-filtered signal; and emphasizing, using a bandwidth switching filter, a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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3. A device, comprising:
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means for creating a synthesized wideband speech signal; and means for enhancing the synthesized wideband speech signal, wherein the means for enhancing comprises; means for post-filtering the synthesized wideband speech signal and outputting a post-filtered signal; and means for emphasizing a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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4. A device comprising:
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a memory; a processor for executing an instruction set stored within the memory, the instruction set for performing the steps of; creating a synthesized wideband speech signal; and enhancing the synthesized wideband speech signal, wherein the enhancing further comprises; post-filtering the synthesized wideband speech signal and outputting a post-filtered signal; and emphasizing, using a bandwidth switching filter, a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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5. A computer-readable medium comprising instructions that are executable by a processor to:
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create a synthesized wideband speech signal; and enhance the synthesized wideband speech signal, wherein the enhancing further comprises; post-filtering the synthesized wideband speech signal and outputting a post-filtered signal; and emphasizing, using a bandwidth switching filter, a mid-range portion of the frequency spectrum of the synthesized wideband speech signal to output a signal with a non-flat frequency spectrum.
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Specification