Publications
Shunting networks for multi-band AM-FM decomposition
October 17, 1999
Conference Paper
Published in:
Proc. IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, 17-20 October 1999.
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Summary
We describe a transduction-based, neurodynamic approach to estimating the amplitude-modulated (AM) and frequency-modulated (FM) components of a signal. We show that the transduction approach can be realized as a bank of constant-Q bandpass filters followed by envelope detectors and shunting neural networks, and the resulting dynamical system is capable of robust AM-FM estimation. Our model is consistent with recent psychophysical experiments that indicate AM and FM components of acoustic signals may be transformed into a common neural code in the brain stem via FM-to-AM transduction. The shunting network for AM-FM decomposition is followed by a contrast enhancement shunting network that provides a mechanism for robustly selecting auditory filter channels as the FM of an input stimulus sweeps across the multiple filters. The AM-FM output of the shunting networks may provide a robust feature representation and is being considered for applications in signal recognition and multi-component decomposition problems.
Summary
We describe a transduction-based, neurodynamic approach to estimating the amplitude-modulated (AM) and frequency-modulated (FM) components of a signal. We show that the transduction approach can be realized as a bank of constant-Q bandpass filters followed by envelope detectors and shunting neural networks, and the resulting dynamical system is capable of...
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A comparative study of existing and proposed FAA and Eurocontrol CHIs for en route air traffic control
September 26, 1999
Conference Paper
Published in:
44th Annual Air Traffic Control Association Conf. Proc., 26-30 September 1999, pp. 22-26.
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Summary
In this paper we present a comparison of the Computer Human Interface (CHI) similarities and differences among the key Free Flight Phase 1 (FFP1) products for en route air traffic control (ATC) and air traffic control management (ATM) as well as some recent Eurocontrol-based CHI innovations. Our comparative study focuses on details of these disparate CHIs and the potential introduction of advanced graphical interactive features seen in the Eurocontrol CHI. Active US controllers who participated in Eurocontrol's Operational Display and Input Development (ODID) study have requested that the FAA develop an alternative CHI based on ODID and its successors such as the Denmark Sweden Interface (DSI). MIT Lincoln Laboratory has built a CHI Requirements Engineering Model (CREM) to support testing of an alternative ODID-like CHI that is feasible given the newly deployed Display System Replacement (DSR).
Summary
In this paper we present a comparison of the Computer Human Interface (CHI) similarities and differences among the key Free Flight Phase 1 (FFP1) products for en route air traffic control (ATC) and air traffic control management (ATM) as well as some recent Eurocontrol-based CHI innovations. Our comparative study focuses...
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An evaluation of the ASR-9 weather channel based on observations from the ITWS prototypes
September 23, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-270
Summary
The Federal Aviation Administration's (FAA) Airport Surveillance Radar (ASR-9) is a high-scan-rate system which provides a "critical" function in terms of air traffic control (ATC). In addition to its primary role of air traffic surveillance, the system also generates precipitation data for display on air traffic specialists' radar scopes and for use by automated systems such as the Integrated Terminal Weather System (ITWS) and Weather Systems Processor (WSP). Air traffic managers use these data to provide optimum routes for aircraft operating in and near the Terminal Radar Approach Control (TRACON) airspace. The primary advantage of the ASR-9 - as an aviation weather radar - over either the Terminal Doppler Weather Radar (TDWR) or the Next Generation Weather Radar (NEXRAD) is the rapid update rate, i.e., 30 seconds, which provides air traffic managers with a more accurate representation of weather echo location within the sensor's domain. This is far superior toeither the TDWR or NEXRAD, which takes from 2.5 to 6 minutes to create a volume scan, depending on the scan strategy. The sensor is also quite reliable, with limited down time. An analysis of ASR-9 data from the ITWS prototypes has uncovered a number of problems, which impact the quality of the precipitation data. The data quality issues discussed are overly aggressive ground clutter suppression, polarization mode issues, hardware failures associated with high beandlow beam switching, attenuatiodsignal depolarization, beam-filling losses, bright- band contamination, distant weather contamination, calibration issues, and radadantenna failures. The recommendations to address the ASR-9 data quality issues can be grouped into three categories: "Variable Site Parameter (VSP)" adjustments, hardware component maintenance checks, and automated flagging of data quality problems. The report includes discussion of the frequency and characteristics of each degradation, presenting both hardware and non- hardware related problems, and concludes with proposed solutions to the problems and recommendations designed to improve the overall utility of the ASR-9 precipitation data.
Summary
The Federal Aviation Administration's (FAA) Airport Surveillance Radar (ASR-9) is a high-scan-rate system which provides a "critical" function in terms of air traffic control (ATC). In addition to its primary role of air traffic surveillance, the system also generates precipitation data for display on air traffic specialists' radar scopes and...
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Operational and spectrum tests for ATIDS at Dallas/Fort Worth Airport
September 20, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-272
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Summary
Runway Incursion (RI) prevention is on the National Transportation Safety Board's (NTSB) list of "10 Most Wanted" safety improvements. Improved surveillance on the airport surface is an important ingredient in that it improves situational awareness and improves the accuracy of tracks used by automation algorithms. Towards this goal, the Runway Incursion Reduction Program (RIRP) has been developing the Airport Target Identification System (ATIDS). ATIDS is a prototype multilateration and Automatic Dependent Surveillance - Broadcast (ADS-B) system. It requires the enabling of existing transponders on the airport surface....The RIRP team, which includes the FAA Volpe National Transportation Systems Center, Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) and Trios Associates, Inc., has conducted interferences tests at Dallas/Fort Worth Airport (DFW) to quantify the impact that ATIDS would have on that high-use environment. The tests included environmental 1040/1090 MHz measurements, ATCRBS false target investigations, and Mode S interrogation tests. This document reports the results of these tests. [Not complete].
Summary
Runway Incursion (RI) prevention is on the National Transportation Safety Board's (NTSB) list of "10 Most Wanted" safety improvements. Improved surveillance on the airport surface is an important ingredient in that it improves situational awareness and improves the accuracy of tracks used by automation algorithms. Towards this goal, the Runway...
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A study of computation speed-ups of the GMM-UBM speaker recognition system
September 5, 1999
Conference Paper
Published in:
6th European Conf. on Speech Communication and Technology, EUROSPEECH, 5-9 September 1999.
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The Gaussian Mixture Model Universal Background Model (GMM-UBM) speaker recognition system has demonstrated very high performance in several NIST evaluations. Such evaluations, however, are concerned only with classification accuracy. In many applications, system effectiveness must be evaluated in light of both accuracy and execution speed. We present here a number of techniques for decreasing computation. Using data from the Switchboard telephone speech corpus, we show that significant speed-ups can be obtained while sacrificing surprisingly little accuracy. We expect that these techniques, involving lowering model order as well as processing fewer speech frames, will apply equally well to other recognition systems.
Summary
The Gaussian Mixture Model Universal Background Model (GMM-UBM) speaker recognition system has demonstrated very high performance in several NIST evaluations. Such evaluations, however, are concerned only with classification accuracy. In many applications, system effectiveness must be evaluated in light of both accuracy and execution speed. We present here a number...
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Evaluation of confidence measures for language identification
September 5, 1999
Conference Paper
Published in:
6th European Conf. on Speech Communication and Technology, EUROSPEECH, 5-9 September 1999.
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Summary
In this paper we examine various ways to derive confidence measures for a language identification system, using phone recognition followed by language models, and describe the application of an evaluation metric for measuring the "goodness" of the different confidence measures. Experiments are conducted on the 1996 NIST Language Identification Evaluation corpus (derived from the Callfriend corpus of conversational telephone speech). The system is trained on the NIST 96 development data and evaluated on the NIST 96 evaluation data. Results indicate that we are able to predict the performance of a system and quantitatively evaluate how well the prediction holds on new data.
Summary
In this paper we examine various ways to derive confidence measures for a language identification system, using phone recognition followed by language models, and describe the application of an evaluation metric for measuring the "goodness" of the different confidence measures. Experiments are conducted on the 1996 NIST Language Identification Evaluation...
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Speaker and language recognition using speech codec parameters
September 5, 1999
Conference Paper
Published in:
EUROSPEECH 99, 5-10 September 1999.
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In this paper, we investigate the effect of speech coding on speaker and language recognition tasks. Three coders were selected to cover a wide range of quality and bit rates: GSM at 12.2 kb/s, G.729 at 8 kb/s, and G.723.1 at 5.3 kb/s. Our objective is to measure recognition performance from either the synthesized speech or directly from the coder parameters themselves. We show that using speech synthesized from the three codecs, GMM-based speaker verification and phone-based language recognition performance generally degrades with coder bit rate, i.e., from GSM to G.729 to G.723.1, relative to an uncoded baseline. In addition, speaker verification for all codecs shows a performance decrease as the degree of mismatch between training and testing conditions increases, while language recognition exhibited no decrease in performance. We also present initial results in determining the relative importance of codec system components in their direct use for recognition tasks. For the G.729 codec, it is shown that removal of the post- filter in the decoder helps speaker verification performance under the mismatched condition. On the other hand, with use of G.729 LSF-based mel-cepstra, performance decreases under all conditions, indicating the need for a residual contribution to the feature representation.
Summary
In this paper, we investigate the effect of speech coding on speaker and language recognition tasks. Three coders were selected to cover a wide range of quality and bit rates: GSM at 12.2 kb/s, G.729 at 8 kb/s, and G.723.1 at 5.3 kb/s. Our objective is to measure recognition performance...
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Modeling of the glottal flow derivative waveform with application to speaker identification
September 1, 1999
Journal Article
Published in:
IEEE Trans. Speech Audio Process., Vol. 7, No. 5, September 1999, pp. 569-586.
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Summary
An automatic technique for estimating and modeling the glottal flow derivative source waveform from speech, and applying the model parameters to speaker identification, is presented. The estimate of the glottal flow derivative is decomposed into coarse structure, representing the general flow shape, and fine structure, comprising aspiration and other perturbations in the flow, from which model parameters are obtained. The glottal flow derivative is estimated using an inverse filter determined within a time interval of vocal-fold closure that is identified through differences in formant frequency modulation during the open and closed phases of the glottal cycle. This formant motion is predicted by Ananthapadmanabha and Fant to be a result of time-varying and nonlinear source/vocal tract coupling within a glottal cycle. The glottal flow derivative estimate is modeled using the Liljencrants-Fant model to capture its coarse structure, while the fine structure of the flow derivative is represented through energy and perturbation measures. The model parameters are used in a Gaussian mixture model speaker identification (SID) system. Both coarse- and fine-structure glottal features are shown to contain significant speaker-dependent information. For a large TIMIT database subset, averaging over male and female SID scores, the coarse-structure parameters achieve about 60% accuracy, the fine-structure parameters give about 40% accuracy, and their combination yields about 70% correct identification. Finally, in preliminary experiments on the counterpart telephone-degraded NTIMIT database, about a 5% error reduction in SID scores is obtained when source features are combined with traditional mel-cepstral measures.
Summary
An automatic technique for estimating and modeling the glottal flow derivative source waveform from speech, and applying the model parameters to speaker identification, is presented. The estimate of the glottal flow derivative is decomposed into coarse structure, representing the general flow shape, and fine structure, comprising aspiration and other perturbations...
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Criteria for sprites and elves based on Schumann resonance observations
July 27, 1999
Journal Article
Published in:
J. Geophys. Res., Vol. 104, No. D14, 27 July 1999, pp. 16,943-16,964.
Summary
Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the measured time constants for lightning charge transfer with the electrostatic relaxation time at altitudes of nighttime sprite initiation (50-70 km) generally validate the electrostatic assumption in predictions made initially by Wilson [1925]. The measured charge moments (Q dS = 200-2000 C-km) are large in comparison with ordinary negative lightning but are generally insufficient to account for conventional air breakdown at sprite altitudes. The measured charge moments, however, are sufficient to account for electron runaway breakdown, and the long avalanche length in this mechanism also accounts for the exclusive association of sprites with ground flashes of positive polarity. The association of elves with large peak currents (50-200 kA) measured by the National Lightning Detection Network in a band pass beyond the Schumann resonance range is consistent with an electromagnetic pulse mechanism for these events.
Summary
Ground flashes with positive polarity associated with both sprites and elves excite the Earth's Schumann resonances to amplitudes several times greater than the background resonances. Theoretical predictions for dielectric breakdown in the mesosphere are tested using ELF methods to evaluate vertical charge moments of positive ground flashes. Comparisons of the...
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The FAA Terminal Convective Weather Forecast product: scale separation filter optimization
July 12, 1999
Conference Paper
Published in:
29th Int. Conf. on Radar Meteorology, 12-16 July 1999.
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Summary
A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay of thunderstorms. The team began work three years ago by evaluating air traffic user needs and requirements. We found that users were willing to trade off forecast accuracy for longer lead times, especially for air traffic management plans that were easy to implement or that incurred low risk (Forman, et al., 1999). The PDT was able to develop an operationally useful forecast product that has been demonstrated in Dallas, TX since March, 1998 (Hallowell, et al., 1999). Further improvements have been made, and testing is now taking place at both Dallas and Orlando, FL. This paper summarizes the basic algorithm methodology and presents quantitative results on optimization of the scale separation filter, which is an integral aspect of the forecast algorithm.
Summary
A large percentage of serious air traffic delay at major airports in the warm season is caused by convective weather. The FAA Convective Weather Product Development team (PDT) has developed a Terminal Convective Weather Forecast product (TCWF) that can account for short-term (out to 60 min) systematic growth and decay...
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