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| Noise eliminating circuit |
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| High common mode relay multiplexer |
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| Loudspeaker having a voice coil and a piezoelectric feedback transducer |
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| Speech recognition apparatus with means for preventing errors due to delay in speech recognition |
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| Electronic musical instrument with manipulation plate |
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| Health club audio system |
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| Sound reproduction system |
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Apparatus for discriminating information signals from noise signals in a communication signal
| Details |
Inventors: Chen, Herbert M.; Hendrickson, Alan F.;
Assignee: Advanced Micro Devices, Inc. (Sunnyvale, CA)
Primary Examiner: Shaw; Dale M.
Assistant Examiner: Knepper; David D.
Attorney, Agent or Firm: Foley & Lardner
The preferred embodiment of the apparatus comprises a first signal level detector which receives the communications signal as an input and generates a detection signal as an output, a second signal level detector which receives the detection signal as an input and generates a noise detection signal as an output, and a comparing circuit which compares the detection signal and the noise detection signal and produces a speech burst detection signal. Each of the signal level detectors comprises a digital low pass filter having an input and an output which employs a comparator for comparing current samples of signals at the input with previous samples of signals at the output and generating a representative comparator output. Each low pass filter includes circuitry for establishing an attack time and a decay time, in response to the comparator output. The attack time and the decay time in the first signal level detector being established as a fast attack time and a slow decay time relative to the attack time and the decay time in the second signal level detector. |
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DETAILED DESCRIPTION OF THE DRAWINGS FIG.
1 is a schematic diagram of an apparatus incorporating the preferred embodiment of the present invention.
FIG.
2 is a schematic diagram of a first embodiment of the present invention.
FIG.
3 is a schematic diagram of the preferred embodiment of the present invention.
FIG.
4 (a)-(c) are illustrations of representative signal wave forms in various loci within the apparatus of FIG.
2.
DETAILED DESCRIPTION OF THE INVENTION In FIG.
1, an apparatus 10 for facilitating communications between an analog device (not shown) and a digital device (not shown) is illustrated.
The apparatus 10 includes a transmit circuit 12, a receive circuit 14, and a control circuit 16.
Transmit circuit 12 includes an analog input 18 from an analog device (not shown), such as a microphone or the like, an analog-to-digital conversion circuit 20, a programmable gain amplifier 22, and a compression circuit 24 for compressing digital signals prior to passing the digital outgoing signals to a digital device (not shown), such as a digital telephone circuit, at output 26.
Also included in transmit circuit 12 are an analog attenuator 30 and a digital attenuator 32.
A booster amplifier 28 is included before analog attenuator 30 to increase the signal-to-noise ratio of the outputting signal before it is treated by analog attenuator 30 or analog-to-digital conversion circuit 20.
Receive circuit 14 receives digital signals from a digital device (not shown), such as a digital telephone network, at digital input 34.
The received digital incoming signal is expanded by an expanding circuit 36 and is amplified by a programmable gain amplifier 38.
Also included in receive circuit 14 is a limiter circuit 40 to limit excursion of the digital incoming signal, a digital-to-analog conversion circuit 42, and an analog output 44.
Analog output 44 is connected to an analog output device (not shown), such as a loudspeaker, or the like.
Also included in receive circuit 14 are an analog attenuator 50 and a digital attenuator 52
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Audio Signal Processing 
