AFA BASED PERIODIC NOISE CANCELLATION

There are many methods for active cancellation of low-frequency periodic noise. Now a new efficient method is investigated. By means of a resonator based observer structure all harmonic components (up to the half of the sampling frequency) can be suppressed. Since the resonator filters out the signal at its own frequency, the rate of suppression is theoretically infinite. Since the system needs a reference signal only to estimate the frequency of the noise to be suppressed, it can be any signal, relatively free of noise, with the same frequency as the primary source. One of the advantages of the method is that the reference source can be either the error sensor, or any other microphone. For the successful noise cancellation the system needs information about the acoustic transfer function, at least its values relatively densely. There was applied a transfer function measurement method based on the resonators. The practical results were obtained by means of a DSP 96002 System Board

Synchronization and sampling in wireless adaptive signal processing systems

This paper deals with the synchronization in wireless adaptive signal processing systems. Wireless communication offers high flexibility, however, the distributed structure of wireless systems requires the synchronization of the subsystems. The synchronization becomes particularly important if the signal bandwidth is in the kHz range, and it is inevitable in distributed control systems. The demand on the synchronization is presented through the introduction of a wireless active noise control system. In this system wireless sensors (microphones) receive the signal, and the main signal processing algorithm is implemented on a central unit which produces the signal for the actuators (loudspeakers). In spite of the special application, the system has a general structure, so the results are valid for other adaptive systems. First a PLL like algorithm is described for the synchronization of the sampling in a wireless real-time signal processing system, then a higher-level synchronization is introduced for a distrib uted Fourier-analyzer based noise control system. The effectiveness of the algorithms is demonstrated by measurement results

Modell alapú digitális jelfeldolgozás = Model Based Digital Signal Processing

Az OTKA támogatás fő célja a doktori értekezésekig eljuttatni az igéretes doktoranduszokat. A pojekt sikeres volt. Publikációs listák: http://www.mycite.omikk.bme.hu/search/index.php?phase=-1 Egyszerű keresés Név Honlapok nem publikált munkaanyagokkal elérhetők a publikációs listákból. Márkus János megvédte Bank Balázs megvédte Valyon József megvédte Tóth Norbert benyújtotta Balogh László tanszéki vitája volt, az utolsó simításokat végzi Kevésbé sikeresek: Székely Nóra publikált, értekezés-részt írt, de nem fejezte be, most szül Dezsényi Csaba részeket írt, mintarendszert dolgozott ki, de nincs készen Vödrös Balázs publikált, mért, "csak"+ a megírás van hátra Molnár Károly publikált, de nem fogott neki Sárhegyi Attila elegendő eredménye és publikációja van, jelenleg amerikai internship-en van, írhatná Lasztovicza László a doktori cselekményt elindította, elegendő publikációja van, de a disszertációval nem halad Ludányi Zoltán abbahagyta Az elején/közepén tart, igéretes: Raikovich Tamás Hullám Gábor Juhász Sándor Orosz György | The aim of the project is to support PhD students in achieving a successful doctoral thesis. Results: Publication lists: http://www.mycite.omikk.bme.hu/search/index.php?phase=-1 Egyszerű keresés (Simple search) Név (Name) Home pages with additional non-published written material are also available from the list Successful work: Márkus, János defended Bank, Balázs defended Valyon, József defended Tóth, Norbert submitted Balogh, László had departmental internal defence, submits now Less successful: Székely, Nóra published, prepared parts, now goes to maternal leave from a firm Dezsényi, Csaba has written parts, created demo system, but not ready - works at a firm Vödrös, Balázs published, measured, has enough material, but writing is very slow Molnár, Károly published, but did not start writing Sárhegyi, Attila has enough results and publications, should write now. He is on internship in the US Lasztovicza, László started doctoral procedure, has enough publications, but doubtful if will write Ludányi, Zoltán quitted In process: Raikovich Tamás Hullám Gábor Juhász Sándor Orosz Györg

Adaptive Filtering with Bandwidth Constraints in the Feedback Path

Abstract This paper introduces a new, adaptive-filter-based controller that shows advantageous properties from the viewpoint of its communication requirement. The algorithm is called signed-error filtered-x LMS (SE-FxLMS). Its novelty is characterized by the fact that it makes possible data compression in the feedback path of adaptive-filter-based control loops in a very simple way. This feature is especially useful in such closed-loop systems where the feedback signals are transmitted over a low-bandwidth communication channel. This is a typical case in so-called networked control systems (NCS) where the communication is carried out over a shared communication channel, e.g., using a wireless sensor network. The paper introduces an analysis of the algorithm as well

Special Issue on “Recent Advances in Indoor Localization Systems and Technologies”

Despite the enormous technical progress seen in the past few years, the maturity of indoor localization technologies has not yet reached the level of GNSS solutions. The 23 selected papers in this special issue present recent advances and new developments in indoor localization systems and technologies, proposing novel or improved methods with increased performance, providing insight into various aspects of quality control, and also introducing some unorthodox positioning methods

Noise-Canceling Office Chair with Multiple Reference Microphones

Office employees are exposed to acoustic noise, especially in an open office environment. Passive or active headsets sufficiently reduce the level of noise, but their long-time wear is uncomfortable. The paper presents an active headrest system built into a chair. Feedforward control is utilized with multiple reference microphones, and flexible gooseneck microphones serve as error sensors. The reference sensors surround the chair, allowing the suppression of sound waves arriving from any direction. The concept of multiple reference control has been tested by extensive experiments showing that multiple reference signals help to increase the suppression in normal rooms where reverberation occurs, even if only one noise source is present. The preliminary experiments are completed by a series of simulations aiming to explore the zones of quiet at the user’s ears. The paper introduces the construction details of the noise-canceling chair: The two loudspeakers are controlled by the signals of two error microphones and four reference signals. The controller is based on the normalized filtered error least mean squared algorithm, implemented on an Analog Devices ADSP-21262 signal processor-based hardware. Experimental results are reported that show the efficient suppression of tonal, as well as broadband disturbances