摘要:
System (10) is disclosed including an acoustic sensor array (20) coupled to processor (42). System (10) processes inputs from array (20) to extract a desired acoustic signal through the suppression of interfering signals. The extraction/suppression is performed by modifying the array (20) inputs in the frequency domain with weights selected to minimize variance of the resulting output signal while maintaining unity gain of signals received in the direction of the desired acoustic signal. System (10) may be utilized in hearing aids, voice input devices, surveillance devices, and other applications.
摘要:
A desired acoustic signal is extracted from a noisy environment by generating a signal representative of the desired signal with a processor. The processor receives aural signals from two sensors each at a different location. The two inputs to the processor are converted from analog to digital format and then submitted to a discrete Fourier transform process to generate discrete spectral signal representations. The spectral signals are delayed by a number of time intervals in a dual delay line to provide a number of intermediate signals, each corresponding to a different spatial location relative to the two sensors. Locations of the noise source and the desired source are determined and the spectral content of the desired signal is determined from the intermediate signal corresponding to the noise source locations. Inverse transformation of the selected intermediate signal followed by digital to analog conversion provides an output signal representative of the desired signal. Techniques to localize multiple acoustic sources are also disclosed. Further, a technique to enhance noise reduction from multiple sources based on two-sensor reception is described.
摘要:
A desired acoustic signal is extracted from a noisy environment by generating a signal representative of the desired signal with processor (30). Processor (30) receives aural signals from two sensors (22, 24) each at a different location. The two inputs to processor (30) are converted from analog to digital format and then submitted to a discrete Fourier transform process to generate discrete spectral signal representations. The spectral signals are delayed to provide a number of intermediate signals, each corresponding to a different spatial location relative to the two sensors. Locations of the noise source and the desired source, and the spectral content of the desired signal are determined from the intermediate signal corresponding to the noise source locations. Inverse transformation of the selected intermediate signal followed by digital to analog conversion provides an output signal representative of the desired signal with output device (90). Techniques to localize multiple acoustic sources are also disclosed. Further, a technique to enhance noise reduction from multiple sources based on two-sensor reception is described.
摘要:
In a data communications network, a split proxy can include a split proxy server disposed behind a firewall in a private portion of the data communications network; a split proxy client disposed in a client computing device positioned externally to the private portion of the data communications network; a split proxy client interface to at least one client application in the client computing device, and a split proxy server interface to at least one server application corresponding to the at least one client application in the private portion of the data communications network. A tunnel can be established between the split proxy client and split proxy server. The tunnel can host all Internet Protocol (IP) data traffic between the client application and the corresponding server application in the private portion of the data communications network.
摘要:
An optical fiber test unit and a method of operating it. The test unit has a laser with a computer controlled excitation current input. To take a measurement, the laser is turned on for a period of time which is approximately equal to twice the propagation time through the fiber. The laser is then turned off and the reflected signal is recorded. This signal is displayed and contains discontinuities which indicate discontinuities in the fiber. The unit provides good dynamic range, but is able to make measurements more rapidly than a conventional OTDR. It is therefore well suited for scan testing of fiber optic cable bundles.
摘要:
A maximum-kurtosis, distortionless response (MKDR) technique and an extension, the maximum-kurtosis, Wiener estimate (MKWE) technique, are provided. In one form, blind estimates of the speech source's channel response are made from the microphone data and MVDR is applied. The source direction is estimated by finding weights that maximize output kurtosis, or the fourth central statistical moment, in the frequency domain. The MKWE approach approximates the Wiener filter by using MKDR-output noise power estimates to compute a Wiener post-filter. These approaches can be extended to block-adaptive versions if the speech source is not quickly moving in space.
摘要:
One embodiment of the invention includes a processing subsystem (30) responsive to the detection of sound coming from a room (26) to establish an acoustic impulse response for the room (26), and determine a number of sound reflections corresponding to the impulse response. This subsystem (30) is further operable to determine volume of the room (26), one or more dimensions of the room (26) and/or at least one absorption coefficient of a room boundary as a function of the sound reflections.
摘要:
Optimum bit rates and power levels are determined for subchannels in multicarrier communication systems. A tangent of the rate-power curve has a slope &lgr;. The slope is defined by the quotient difference between high/low power and high/low rate. A particular &lgr; is evaluated to find its corresponding total power followed by an update of &lgr;, in the form of an increase or decrease, to get closer to the optimal solution. Each &lgr; is evaluated to find the optimal operating point for each subchannel on the rate-power curve by summing the power allocated to the subchannels, and comparing the result to the power budget. Look-up tables are stored for individual channels, but similarity between channels permits joint use of look-up tables by multiple channels. The tables are used to determine the rate-power characteristics at each iteration. An optimal solution is found when either a newly chosen power allocation meets the power budget exactly or a newly chosen power budget equals the high or low power of a previous iteration.
摘要:
Method and apparatus for adaptive filtering a first signal to produce a second signal that approximates a desired signal including an acoustic charge transport type programmable transversal filter (PTF) having a number of taps where each tap corresponds to an associated delayed first signal and each tap having means for providing a variable tap weight to modify the filter response. The first signal is coupled to the PTF and the output of the PTF produces the second signal. A summer compares the output of the PTF and the desired signal to produce an error signal. A programmable delay line has time delays programmable to integer multiples of the PTF tap spacing to provide a delayed version of the first signal, and a multiplier multiplies the error signal and the delayed input of the programmable delay line to produce a gradient signal. The gradient signal is filtered with an analog lowpass filter to produce a filtered gradient signal which in turn is converted to a digital signal by a low bandwidth analog to digital converter. A microprocessor implements a filtered gradient algorithm to update the PTF filter tap, load the new tap weight into the PTF, and reconfigure the programmable delay line to produce a filtered gradient for another tap. The comparison of the PTF output with the desired signal continues to develop an error signal and the adaptive process is repeated until the error signal becomes substantially zero which results in the second signal more closely approximating the desired signal.
摘要:
An electron spectroscopy system is disclosed which is specially suited for chemical analysis of electrically isolated specimens. X-rays or other ionizing radiation is focused to a relatively small spot on the surface of the electrically isolated sample to be analyzed. An electron energy analyzer has its input optics focused such that the input field of view of the electron energy analyzer is coincident with the beam spot produced by the focused beam of ionizing radiation on the specimen so as to capture secondary photoelectrons emitted from the surface of the sample under analysis. The energies of the secondary photoelectrons are analyzed to obtain a spectrum of the constituents of the surface of the sample under analysis. A flood beam of relatively low energy electrons is directed onto the surface of the sample for neutralizing the positive surface charge in the region of the beam spot. An electrically conductive grid is positioned in closely spaced relationship to the surface of the sample for smoothing the gradients in the electrical potential in the region of the beam spot, thereby improving the resolution of the secondary photoelectron energy spectrum obtained from the sample under analysis.