6 research outputs found

    Communication system with adaptive noise suppression

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    A signal-to-noise ratio dependent adaptive spectral subtraction process eliminates noise from noise-corrupted speech signals. The process first pre-emphasizes the frequency components of the input sound signal which contain the consonant information in human speech. Next, a signal-to-noise ratio is determined and a spectral subtraction proportion adjusted appropriately. After spectral subtraction, low amplitude signals can be squelched. A single microphone is used to obtain both the noise-corrupted speech and the average noise estimate. This is done by determining if the frame of data being sampled is a voiced or unvoiced frame. During unvoiced frames an estimate of the noise is obtained. A running average of the noise is used to approximate the expected value of the noise. Spectral subtraction may be performed on a composite noise-corrupted signal, or upon individual sub-bands of the noise-corrupted signal. Pre-averaging of the input signal's magnitude spectrum over multiple time frames may be performed to reduce musical noise

    Adaptive Suppression of Noise in Voice Communications

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    A subsystem for the adaptive suppression of noise in a voice communication system effects a high level of reduction of noise that enters the system through microphones. The subsystem includes a digital signal processor (DSP) plus circuitry that implements voice-recognition and spectral- manipulation techniques. The development of the adaptive noise-suppression subsystem was prompted by the following considerations: During processing of the space shuttle at Kennedy Space Center, voice communications among test team members have been significantly impaired in several instances because some test participants have had to communicate from locations with high ambient noise levels. Ear protection for the personnel involved is commercially available and is used in such situations. However, commercially available noise-canceling microphones do not provide sufficient reduction of noise that enters through microphones and thus becomes transmitted on outbound communication links

    Unmanned Aviation Systems Models of the Radio Communications Links: Study Results - Appendices Annex 2. Volume 1 and Volume 2

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    This report describes the analysis of communications between the Control Station and an Unmanned Aircraft (UA) flying in the National Airspace System (NAS). This work is based on the RTCA SC-203 Operational Services and Environment Description (OSED). The OSED document seeks to characterize the highly different attributes of all UAs navigating the airspace and define their relationship to airspace users, air traffic services, and operating environments of the NAS. One goal of this report is to lead to the development of Minimum Aviation System Performance Standards for Control and Communications. This report takes the nine scenarios found in the OSED and analyzes the communication links

    Measurement of the Mass of the Z-Boson and the Energy Calibration of Lep

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    Contains fulltext : 26847___.PDF (publisher's version ) (Open Access

    Measurement of the mass of the Z boson and the energy calibration of LEP

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    In 1985 the French government created a unique circuit for the dissemination of doctoral theses: References went to a national database “Téléthèses” whereas the documents were distributed to the university libraries in microform. In the era of the electronic document this French network of deposit of and access to doctoral theses is changing. How do you discover and locate a French thesis today, how do you get hold of a paper copy and how do you access the full electronic text? What are the catalogues and databases referencing theses since the disappearance of “Téléthèses”? Where are the archives, and are they open? What is the legal environment that rules the emerging structures and tools? This paper presents national plans on referencing and archiving doctoral theses coordinated by the government as well as some initiatives for creating full text archives. These initiatives come from universities as well as from research institutions and learned societies. “Téléthèses” records have been integrated in a union catalogue of French university libraries SUDOC. University of Lyon-2 and INSA Lyon developed procedures and tools covering the entire production chain from writing to the final access in an archive: “Cyberthèses” and “Cither”. The CNRS Centre for Direct Scientific Communication at Lyon (CCSD) maintains an archive (“TEL”) with about 2000 theses in all disciplines. Another repository for theses in engineering, economics and management called “Pastel” is proposed by the Paris Institute of Technology (ParisTech), a consortium of 10 engineering and commercial schools of the Paris region
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