Search results for "Noise control"
showing 10 items of 16 documents
Experimental investigation of holes interaction effect on the sound absorption coefficient of micro-perforated panels under high and medium sound lev…
2011
Abstract This paper experimentally investigates the holes interaction effect on the sound absorption coefficient of micro-perforated panels under high and medium sound levels. The theoretical formulations are based on a semi-empirical approach and the use of Fok’s function to model the acoustic surface impedance. For the high sound level regime, an empirical power law involving three coefficients is adapted. It is shown theoretically and experimentally that these coefficients can lead to optimized absorption performance and particularly, a formula relating the critical Reynolds number (Reynolds number value after which the absorption coefficient decreases with the increase of sound level) a…
FPGA Implementation of an Adaptive Filter Robust to Impulsive Noise: Two Approaches
2011
Adaptive filters are used in a wide range of applications such as echo cancellation, noise cancellation, system identification, and prediction. Its hardware implementation becomes essential in many cases where real-time execution is needed. However, impulsive noise affects the proper operation of the filter and the adaptation process. This noise is one of the most damaging types of signal distortion, not always considered when implementing algorithms, particularly in specific hardware platforms. Field-programmable gate arrays (FPGAs) are used widely for real-time applications where timing requirements are strict. Nowadays, two main design processes can be followed for embedded system design…
Control of Acoustical Quality of Indoor Spaces: Thorough Analysis of the Influence of Façade Typologies
2001
Building shape is of prime importance with regard to the acoustic aspects of achieving adequate indoor environmental quality. This paper presents experimental results obtained in a measurement programme carried out at CSTB, using reduced-scale models. The objectives were to identify the architectural forms of façades' best for noise mitigation, and to address the influence of façade architecture on indoor acoustic quality. Many façade typologies have been assessed in different situations involving combinations of structural and architectural elements, such as balustrades, balconies, loggias, etc. A systematic simulation of real configurations (buildings in front of one another, stacked or …
Background noise suppression for acoustic localization by means of an adaptive energy detection approach
2008
A microphone array can be employed to localize dominant acoustic sources in a given noisy environment. This capability is successfully used in good signal to noise ratio (SNR) conditions but its accuracy decreases considerably in the presence of other background noise sources. In order to counteract this effect, a novel approach that combines the information provided by a Gaussian energy detector (GED) with the approved localization method SRP-PHAT is presented in this paper. To evaluate the presented technique, several acoustic sources (speech and impulsive sounds) were considered in a variety of different scenarios to demonstrate the robustness and the accuracy of the system proposed.
Efficient FPGA Implementation of an Adaptive Noise Canceller
2006
A hardware implementation of an adaptive noise canceller (ANC) is presented. It has been synthesized within an FPGA, using a modified version of the least mean square (LMS) error algorithm. The results obtained so far show a significant decrease of the required gate count when compared with a standard LMS implementation, while increasing the ANC bandwidth and signal to noise (S/N) ratio. This novel adaptive noise canceller is then useful for enhancing the S/N ratio of data collected from sensors (or sensor arrays) working in noisy environment, or dealing with potentially weak signals.
Online mass flow prediction in CFB boilers
2009
Fuel feeding and inhomogeneity of fuel typically cause process fluctuations in the circulating fluidized bed (CFB) process. If control systems fail to compensate for the fluctuations, the whole plant will suffer from fluctuations that are reinforced by the closed-loop controls. This phenomenon causes a reduction of efficiency and lifetime of process components. Therefore, domain experts are interested in developing tools and techniques for getting better understanding of underlying processes and their mutual dependencies in CFB boilers. In this paper we consider an application of data mining technology to the analysis of time series data from a pilot CFB reactor. Namely, we present a rather…
Foetal ECG recovery using dynamic neural networks
2002
Non-invasive electrocardiography has proven to be a very interesting method for obtaining information about the foetus state and thus to assure its well-being during pregnancy. One of the main applications in this field is foetal electrocardiogram (ECG) recovery by means of automatic methods. Evident problems found in the literature are the limited number of available registers, the lack of performance indicators, and the limited use of non-linear adaptive methods. In order to circumvent these problems, we first introduce the generation of synthetic registers and discuss the influence of different kinds of noise to the modelling. Second, a method which is based on numerical (correlation coe…
Implementation of a new adaptive algorithm using fuzzy cost function and robust to impulsive noise
2012
Adaptive filters are used in a wide range of applications such as noise cancellation, system identification, and prediction. One of the main problems for theses filters is the impulsive noise as it generates algorithm unstability. This work shows the development, simulation and hardware implementation of a new algorithm robust to impulsive noise. Hardware implementation becomes essential in many cases where a real time execution, reduced size, or low power system is needed. An efficient hardware architecture is proposed and different optimizations for size and speed are developed: no need for control state machine, reduced computation requirements due to simplifications, etc. Furthermore, t…
Sub-kelvin current amplifier using DC-SQUID
2000
Abstract We have set up a system where a low-noise DC-SQUID is used as a current amplifier. The SQUID output is read using a wide band electronics unit based on the noise cancellation scheme. The SQUID has been installed in a compact Nanoway PDR50 dilution refrigerator, and superconducting transitions of Ti/Au thermometer strips for X-ray calorimeter applications have been measured. We can operate at 100 mK using a SQUID with Pd shunt resistors. Noise and bandwidth results of the setup are presented.
Modelling and Simulation of Ego-Noise of Unmanned Aerial Vehicles
2020
In this paper, we develop a simulation model for the ego-noise of unmanned aerial vehicles (UAVs). The ego-noise is composed of spike noise and background noise. The spike noise is modelled by a finite sum of sinusoids, while the background noise is modelled by a coloured Gaussian stationary process. The main property of our model is that it only depends on physical characteristics of the UAV and it does not need real-time audio inputs to be developed. This model is very useful for training novel noise cancelling algorithms and for evaluating their performance. To validate the proposed model, we compare the statistical properties of the ego-noise simulated using our model with actual ego-no…