Wyniki wyszukiwania - BazTech

1

Estimation method for measurements with heavy-tailed noise variance

Jańczak D.

Przegląd Elektrotechniczny

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2017

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R. 93, nr 12

22--25

EN

The paper presents a new method of signal estimation in systems with measurement channel corrupted by noise which variance is random process with heavy-tailed distribution. The noise model provides a description of the wide range of interference occurring in telecommunication systems. The proposed estimation algorithm is based on the multi-Gaussian approximation. The results of the simulation tests showed high efficiency of the method and its low numerical load.

PL

W artykule zaproponowano metodę estymacji sygnału w przypadku gdy wariancja szumu pomiarowego opisana jest rozkładem gruboogonowym. Rozważany model szumu pozwala na opis szerokiego zakresu zakłóceń pojawiających się w systemach telekomunikacyjnych. Proponowana metoda oparta jest na aproksymacji wielogaussowkiej. Wyniki badań symulacyjnych, wykazały wysoką skuteczność proponowanej metody i niskie obciążenie numeryczne.

2

Earplug Actuator Selection for a Miniature Personal Active Hearing Protection System

Pawełczyk M., Latos M.

Archives of Acoustics

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2010

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Vol. 35, No. 2

213-222

EN

There are many industrial environments which are exposed to a high-level noise. It is necessary to protect people from the noise. Most of the time, the consumer requires a miniature version of a noise canceller to satisfy the internal working place requirements. Very important thing is to select the most appropriate personal hearing protection device, for example an earplug. It should guarantee high passive noise attenuation and allow for secondary sound generation in case of active control. In many cases the noise is nonstationary. For instance, some of the noisy devices are switched on and off, speed of some rotors or fans changes, etc. To avoid any severe transient acoustic effects due to potential convergence problems of adaptive systems, a fixed-parameter approach to control is appreciated. If the noise were stationary, it would be possible to design an optimal control filter minimising variance of the signal being the effect of the acoustic noise and the secondary sound interference. Because of noise nonstationarity for most applications, the idea of generalised disturbance defined by a frequency window of different types has been developed by the authors and announced in previous publications. The aim of this paper is to apply such an approach to different earplugs and verify its noise reduction properties. Simulation experiments are conducted based on real world measurements performed using the G.R.A.S. artificial head equipped with an artificial mechanical ear, and the noise recorded in a power plant.

3

Adaptive Algorithms for Enhancement of Speech Subject to a High-Level Noise

Latos M., Pawełczyk M.

Archives of Acoustics

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2010

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Vol. 35, No. 2

203-212

EN

There are many industrial environments which are exposed to a high-level noise, sometimes much higher than the level of speech. Verbal communication is then practically unfeasible. In order to increase the speech intelligibility, appropriate speech enhancement algorithms can be used. It is impossible to filter off the noise completely from the acquired signal by using a conventional filter, because of two reasons. First, the speech and the noise frequency contents are overlapping. Second, the noise properties are subject to change. The adaptive realisation of the Wienerbased approach can be, however, applied. Two structures are possible. One is the line enhancer, where the predictive realisation of the Wiener approach is used. The benefit of using this structure it that it does not require additional apparatus. The second structure takes advantage of the high level of noise. Under such condition, placing another microphone, even close to the primary one, can provide a reference signal well correlated with the noise disturbing the speech and lacking the information about the speech. Then, the classical Wiener filter can be used, to produce an estimate of the noise based on the reference signal. That noise estimate can be then subtracted from the disturbed speech. Both algorithms are verified, based on the data obtained from the real industrial environment. For laboratory experiments the G.R.A.S. artificial head and two microphones, one at back side of an earplug and another at the mouth are used.

4

Feedforward vs. Feedback Fixed-Parameter H2 Control of Non-Stationary Noise

Latos M., Pawełczyk M.

Archives of Acoustics

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2009

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Vol. 34, No. 4

521-535

EN

Stationary random noise can be modelled as a wide-sense stationary white noise filtered by a minimum phase filter. Such filter can be used to design an optimal control filter minimising variance of the signal being the effect of the noise and the secondary sound interference. However, in many environments the noise is subject to change. For instance, some of the noisy devices are switched on and off, speed of some rotors or fans changes, etc. As a result contribution of different frequency components may significantly vary in time. Solving the optimisation problem to update control filter is rather avoided in on-line systems. In adaptive approach there are problems with convergence or some unpleasant transient acoustic effects. In this paper, the fixed-parameter approach to control is appreciated. Dominating frequency components/bands can usually be distinguished for the acoustic environment. Then, the idea of generalised disturbance defined by a frequency window of different type can be applied. If a reference signal, correlated with the disturbance to be reduced is available in advance, a feedforward structure can be applied, and otherwise, a feedback structure is used. Spectral and inner-outer factorisations are employed in order to cope with non-minimum phase character of the acousto-electric plant. Efficiency of the proposed approach for both control structures is verified based on the data obtained from an active personal headset. The generalised disturbance based control systems are confronted with the classical Wiener control systems designed for the given disturbance.